Triassic critters, Madygen & Co.

Madygen freshwater sharks made the JVP front page

2011-09-10T05:53:00.000-07:00

Fischer, J., S. Voigt, J. W. Schneider, M. Buchwitz & S. Voigt (2011): A selachian freshwater fauna from the Triassic of Kyrgyzstan and its implication for Mesozoic shark nurseries. Journal of Vertebrate Paleontology 31: 937- 953. [Abstract]

Aha: Egg capsules and microvertebrate fossils can be a worthwile study object after all. (Event though Jan Fischer, my fellow grad student at the Geological Institute in Freiberg, had an interview with a critical local newsreporter who doubted that anybody could ever be interested in something like that.)

Jan and colleagues describe chondrichthyan egg capsule fossils from the Madygen Formation and refer them to Palaeoxyris, a capsule type usually assigned to hybodont sharks, and Fayolia, probably produced by xenacanth sharks. These fossils are accompagnied by nearby finds teeth of hybodont shark teeth - most of them are tiny and probably belonged to juveniles of the newly erected species Lonchidion ferganensis.

Oxygen isotope analysis of the teeth and their comparison to hybodont teeth from other localities yields a clear freshwater signal for the Madygen samples, indicating that the shark offspring indeed inhabited a freshwater habitat.

Facial analysis of the sedimentary succession of the Madygen Formation demonstrates the presence of wide-spread shallow and vegetated shore areas during the Middle Triassic which could have functioned as a shark nursery, i.e. a separate and ecologically distinct habitat for juveniles which was not invaded by adult sharks of the same species.

Triassic cicadomorph insects with camouflage

2011-05-10T06:10:00.000-07:00

Shcherbakov, D. 2011. New and little-known families of Hemiptera Cicadomorpha from the Triassic of Central Asia – early analogs of treehoppers and planthoppers. Zootaxa 2836: 1-26. [article preview with abstract]

Dmitry Shcherbakov describes twelve new (monotypic) genera and species of cicadomorphs from the Madygen Formation on the basis of some exquisitely preserved fossils and redescribes three others.

He finds homoplastic similarities of the fossil families Saaloscytinidae and Maguviopseidae (newly erected) to leaf hoppers and tree hoppers (Membracoidea) and of Mesojabloniidae to plant hoppers (Fulgoroidea)

Convergent to the extant groups of cicadomorphs the newly described fossil taxa use different means of camouflage, namely bizarrely-shaped tegmina (singular 'tegmen' = anterior cover wings without aerodynamic function), dorsal projections on the thorax and tegmen, well-developed surface sculpture, and (dull) coloration. According to Shcherbakov the specific morphology of the Maguviopseidae and Saaloscytinidae mimicked thorns, bracts, seed-bearing organs, seeds, buds, or leaves, whereas the Mesojabloniidae mimicked rotten wood or bark.

Shcherbakov assumes that predation by tree-living reptiles, such as Sharovipteryx and Longisquama (which are known from the same locality within the Madygen Formation), was an important factor underlying the evolution of elaborate types of camouflage.

As none of these Triassic hoppers appear to have survived for long, Shcherbakov concludes that their extinction was linked to the extinction of the host plants whose plant organs they imitated.

A palaeodictyopteran and other relics from Madygen

2011-04-10T06:42:00.000-07:00

Béthoux, O., S. Voigt, and J. W. Schneider. 2010. A Triassic palaeodictyopteran from Kyrgyzstan. Palaeodiversity 3: 9-13. [pdf 1.5 Mb]

Despite the substantial collection and study of insect fossils from the Madygen Formation (see overview in Shcherbakov 2008a) there are still unkown elements of the entomofauna left. Béthoux et al. (2010) describe a wing of a not yet reported group of insects from lacustrine shales of the northwestern ouctrop area of the Madygen Fm. (which also yielded Sharovipteryx and Longisquama).

Ruling out all alternatives on the basis of wing venation data, they come to the conclusion that reliquia spec. nov. was a late member of Palaeodictyoptera, an order-rank group according to conventional classification schemes that was previously thought to have died out during the Middle or Late Permian.

Béthoux et al. suggest that the disappearance of ancient insect groups in equatorial realms is linked to the Late Paleozoic aridisation in these areas that triggered the migration to wetter higher latitude ecosystems, such as the Madygen lake environment. The relatively late occurence of paleodictyopterans in Madygen is also in agreement with Shcherbakov's (2008b) hypothesis that the renewal of Triassic entomofaunas was asynchronous, starting in the lower latitudes and spreading to the higher latitudes.

Other Madygen relics?

Apart from modern groups, such as dipterans and hymenopterans among insects as wells as lissamphibians and archosaurs among tetrapods there are further relict forms, such as the choniosuchian Madygenerpeton or the basal cynodont Madysaurus. As hinted by Béthoux et al. the question to what degree and why Madygen functioned as a refugium is still to be answered.

Chroniosuchia: Paper on osteoderm histology in online preview

2011-03-30T16:24:00.000-07:00

...my first experience with bone histology:

Buchwitz, M., Witzmann, F., Voigt, S. & Golubev, V. in press. Osteoderm microstructure indicates the presence of a crocodylian-like trunk bracing system in a group of armoured basal tetrapods. Acta Zoologica, DOI: 10.1111/j.1463-6395.2011.00502.x

Abstract. The microstructure of dorsal osteoderms referred to the chroniosuchid taxa Chroniosuchus, Chroniosaurus, Madygenerpeton and cf. Uralerpeton is compared to existing data on the bystrowianid chroniosuchian Bystrowiella and further tetrapods. Chroniosuchid osteoderms are marked by thin internal and relatively thick external cortices that consist of lowly vascularised parallel-fibred bone. They are structured by growth marks and, in case of Madygenerpeton, by lines of arrested growth. The cancellous middle region is marked by a high degree of remodelling and a primary bone matrix of parallel-fibred bone that may include domains of interwoven structural fibres. Whereas the convergence of Bystrowiella and chroniosuchid osteoderms is not confirmed by our observations, the internal cortex of the latter displays a significant peculiarity: It contains distinct bundles of shallowly dipping Sharpey’s fibres with a cranio- or caudoventral orientation. We interpret this feature as indicative for the attachment of epaxial muscles which spanned several vertebral segments between the medioventral surface of the osteoderms and the transversal processes of the thoracic vertebrae. This finding endorses the hypothesis that the chroniosuchid osteoderm series was part of a crocodylian-like trunk bracing system that supported terrestrial locomotion. According to the measured range of osteoderm bone compactness, some chroniosuchian species may have had a more aquatic lifestyle than others.

Maths in Paleontology (I): Data

2011-02-11T08:00:00.000-08:00

''In every special doctrine of nature only so much science proper can be found as there is mathematics in it.'' - Immanuel Kant, Metaphysical Foundations of Natural Science (1786)

Warningly the maths professor who got the unthankful task to teach us first-semester scientists-to-be some basic basics of his field chose Kant's statement as the first in his first lecture on "higher" maths. However, when I started my studies in geology and paleontology, there was another saying among old school geology teachers: "A bad mathematician makes a good geologist."

Many a fellow student were rather willing to believe in these latter words than in the inconvenient alternative. (I always considered this believe as outdated and I got the feeling that geology as a science might have been shaped not only by the talents of its protagonists but also by their limitations in terms of exactness and rigorousity.)

Luckily you were not necessarily considered as a bad geologist if you were interested in maths and the notion that modern geoscience involves maths and exact methods (e.g. methods of quantitative data analysis, databases, multivariate statistics and geostatistics, geoinformatics and geographic information systems, 3D and 4D modelling, remote sensing) was clearly on the rise. Perhaps from a biologists' point of view this story would be different, but, to tell you the truth, some of the biology-based paleontologists I got to know are not much living on the exact side either.

Apart from microscopy seminars, field, and lab practicals which teach you ways of data acquisition some classes in statistics and data analysis during first semesters of study give you an idea about the structure of data and ways how to sample and how to deal with data in order to find new knowledge, e.g. a relationship between two phenomena previously not considered to be related.

At the very beginning you will learn that there are different types of data used in paleontology and that you have to bring your data into shape for any kind of mathematical analysis tools, i.e. arrange them as a data table such as the following:

Specimen	Class	State of XYZ	No. of UVW	size L [mm]	size M [cm²]
A	a	Aa	2	12.1	234
B	b	B	3	13.3	87
...	...	...	...	...	...
X	x	X	...	...	...

Normally lines of the table represent samples (or groups of samples or taxa) whereas columns may represent various features or measures. Such features may be the belonging to a certain class or category or the presence, absence, or specificity of a feature. Measured values as entries may have a discrete contribution (e.g. natural numbers such as the number of teeth or segments or body chambers) or a continuous distribution (e.g. length, area, angle, temperature measurements).

Various data relevant for paleontologists can be arranged as tables, such as morphological and microstructural data, stable isotope and other geochemical data, geographical, sedimentological, and stratigraphic data, as well as taphonomic and paleoecological data. Some of these data have a special structure and can be referred to one of the following types:

Compositional data...

... add up to 100%. Chemical compositions of fossils or faunal compositions are compositional data:

Community	Trilobites	Brachiopods	Echinoderms	Poriferans	Nautiloids
A	23 [%]	42	17	5	13
B	10	15	5	50	20
...	...	...	...	...	...
X	...	...	...	...	...

These data require careful considerations and a special kind of maths because all variables are (necessarily) correlated and thus an alleged dependence, e.g. of brachiopod and echinoderm abundances, can be obscured by variation in another group.

Spatially or temporally correlated data

‘Spatial correlation’ means that values for data points close to each other are more similar than values of more distant data points – e.g. the faunal composition of an ecosystem from Arizona is rather like that of a Nevada community than that of a Massachusetts community.

Locality	Easting (X)	Northing (Y)	Facies	Archosaurs [%]	Rhynchosaurs [%]
A	5687	0487	lacustrine	23	45
B	6485	0808	fluviatile	34	38
C	6800	1490	fluviatile	40	37
...	...	...	...	...	...

Geostatistics is the usual method to deal with spatially correlated data. Spatial correlation can also occur on much smaller scales, e. g. the shape and size of two skull bones in contact to each other can show a stronger dependence than the shape and size of bones that are more distant to each other.

In paleontology temporal correlation is quite abundant, especially if your study considers different stratigraphic ages or sedimentological field data:

Population	Horizon	Ar/Ar age [Ma]	Facies	δ¹⁸O [‰]	Average size [mm]
A	1	210 ± 1	deltaic	-2.0	5.2
B	2a	N/A	distal shelf	1.4	6.4
C	2c	207 ± 2	?	2.1	6.8
D	4	200 ± 1	deltaic	-2.2	6.0

As in stockmarket analytics methods of time series analysis can be applied to interpret temporally correlated data (i.e. time series). Such data may be relevant for your study as they often indicate evolutionary trends (biological evolution in the stricter sense but also evolution of paleoenvironments), cyclic processes with a certain periodicity, and/or they can form the basis for relating contemporaneous processes in the geological past (e.g. stratigraphic correlation of separate sedimentary successions).

Orientation data

For elongated fossils such as conical shells or long bones the orientation of the fossil long axis towards the geographical cordinate system can be measured using a compass (with inclinometer). In a similar way the orientation of bedding planes can be documented. Such measurements are often used for the purpose of deducing the former transport direction of a ancient sediment transport and depostion system (such as a river, delta, or alluvial fan). A data table with orientation data may look like that:

Specimen No.	Description	Length [cm]	Horizon	Azimuth>	Dip
1	long bone	21	1	N 20° E	0°
2	rib	12	1	N 10° W	5°
3	calamite stem	80	2a	N 15° E	0°
...	...	...	...	...	...

“Azimuth” refers to the angle towards north. Orientation data are distributed on a halfsphere. Mean values (e.g. the average orientation of long bones) and other distribution parameters cannot be derived directly from the averaging of orientation angles but vector arithmetics has to be applied.

Cladistic data

Phylogeny on the basis of morphology conventionally involves cladistic methods, especially in the field of vertebrate paleontology which deals with a particular character-rich group that is deemed suitable for cladistic approaches employing certain kinds of analysis software specialized for the calculation of phylogenetic trees (e.g. PAUP, WinClada).

In cladistic datasets lines represent taxa, mostly species or genera of the group of interest, and columns represent characters (ordered by number), i. e. features of the skeleton which are variable among the included taxa:

Taxon	1	2	3	4	5	6	7	8	9	10
A-saurus	0	0	0	0	0	0	1	0	?	0
B-raptor	?	0	1	?	0	0	1	1	0	0
C-onyx	1	1	0	?	-	1	-	1	0	1
D-ops	1	1	2	1	1	1	1	0	1	1
E-mimus	0	-	2	1	1	2	0	0	1	1

One of the main issues in cladistics is the definition of characters and the correct (unbiased) coding of morphological information. You can include qualitative differences ("bone X contacts bone Y but not bone Z" = character state “0”; "bone X contacts bones Y and Z" = character state “1”) and quantitative differences ("length of metatarsal 3 larger than or as large as length of metatarsal 4" = character state "0"; "mt3 is shorter than mt4" = "1"). Sometimes mixed character states like "0 or 1 [but not 2]" occur in a taxon and are coded accordingly.

Missing data...

...occur all the time in paleontology ... either because specimens are not complete enough or because their geological age cannot be exactly determined or because specimens are too rare or valuable to use them for a destructive analysis method or because they are for some reason no longer accessible. "N/A" ("not applicable") or empty entries or question marks often symbolize missing data.

Some introductory literature:

Borradaile, G. J. 2003. Statistics of Earth Science Data. Springer, Berlin, 280 pages. ISBN 3540436030

Swan, A. R. H. and M. Sandilands. 1995. Introduction to geological data analysis. Blackwell, Oxford, 446 pages. ISBN 0632032243

New paper on cycadophytes from Madygen

2011-01-16T13:06:00.000-08:00

Moisan, P., S. Voigt, C. Pott, M. Buchwitz, J. Schneider, and H. Kerp. in press. Cycadalean and bennettitalean foliage from the Triassic Madygen Lagerstätte (SW Kyrgyzstan, Central Asia). Review of Palaeobotany and Palynology. [DOI:10.1016/j.revpalbo.2010.11.008]

Philippe Moisan who is doing his Ph.D. in Münster (with paleobotanist Hans Kerp as his supervisor) studies the flora of the Triassic Madygen Fm. In his first paper on that issue he introduces cycadophyte finds collected between 2005 and 2009.

Many of the studied the specimen come from the same succession and locality as Madygenerpeton (there is also a small sketch of the sedimentary profile, see Fig. 2).

One thing I learned from this study was that so-called "xeromorphic features", i.e. plant features that are usually the consequence of an adaptation to aridity, cannot only occur in xerophytes, i.e. in plants adapted to dry environments, but (for other reasons) in hygrophytic and halophytic plants as well.

Indications for aridity, such as desiccation crack horizons or or seasonally drying-out ponds and rivers or wide-spread red bed sediments are lacking in Madygen. Thus, according to Philippe's interpretation, "xeromorphism" in Madygen plants probably served other purposes than the xeromorphism of xerophytes (e.g. "self-cleaning of the leaf surface, regulation of excessive radiation and leaf temperature, mechanical defense against phytophagous insects").

Three recent papers on chroniosuchians

2010-12-02T21:37:00.000-08:00

Buchwitz M, Voigt S. 2010. Peculiar carapace structure of a Triassic chroniosuchian implies evolutionary shift in trunk flexibility. Journal of Vertebrate Paleontology 30: 1697-1708. [Link]

Schoch RR, Voigt S, Buchwitz M. 2010. A chroniosuchid from the Triassic of Kyrgyzstan and analysis of chroniosuchian relationships. Zoological Journal of the Linnaean Society 160: 515-530. [Link]

Klembara J, Clack J, Čerňanský A. 2010. The anatomy of palate of Chroniosaurus dongusensis (Chroniosuchia, Chroniosuchidae) from the Upper Permian of Russia. Palaeontology 53: 1147-1153. [Link]

The redescription of the Chroniosaurus dongusensis palate by Klembara and colleagues adds further data to the morphological dataset provided by Clack and Klembara (2009) in their revision of C. dongusensis on the basis of a new specimen (which is the most complete of any yet known chroniosuchian). According to the updated phylogenetic analysis from the 2010 paper Chroniosaurus as the only included chroniosuchian taxon formed the sister group of embolomeres.

Schoch and colleagues (me included) describe Madygenerpeton pustulatus, a new species of chroniosuchians from the Middle to Late Triassic of Central Asia with a highly derived skull morphology and a carapace that was chroniosuchid-like in many aspects. The find shows that one lineage of chroniosuchids survived the Permian-Triassic boundary (by 20 or so million years).

The authors discuss characteristics uniting chroniosuchians with "higher reptiliomorphs" and unlike the approach of Klembara and colleagues their cladistic analysis, which includes five chroniosuchian taxa, results in a position of chroniosuchians somewhat closer to amniotes than to embolomeres. Chroniosaurus comes out as the closest relative of Madygenerpeton (both share the characteristic ornamentation of the skull and osteoderms besides other features).

Buchwitz & Voigt consider the functionality of chroniosuchian carapaces, comparing them to archosaur osteoderm systems. They argue that chroniosuchian carapaces basically served terrestrial locomotion but that the higher lateral flexibility of the Madygenerpeton osteoderm system was linked to a secondary increase in undulation swimming capability.

Reference:
Clack JA, Klembara J. 2009. An articulated specimen of Chroniosaurus dongusensis, and the morphology and relationships of the chroniosuchids. Special Papers in Palaeontology 81: 15-42. [Link]

Palges Meeting October 2010 in Munich

2010-10-30T15:52:00.000-07:00

The 80 th Annual Meeting of the German Paleontological Society took place from the 6th through the 8th October 2010 within the halls of the Bavarian State Collection for Geology and Paleontology in Munich.

Of particular interest for me was the session on Early Mesozoic vertebrates chaired by the Rauhut couple and Richard Butler as it united many interesting characters, such as Silvio Renesto, Martin Ezcurra, Rainer Schoch, and Daniela Schwarz-Wings and covered a variety of Triassic vertebrates including archosaurs, temnospondyls, and bony fish.

With 5 talks and 6 posters our small Freibergian working group had quite a number of contributions this year (my prof Jörg Schneider was talking about Paleozoic cockroaches from China, Olaf Elicki about Cambrian trace fossils from Africa and the Middle East, Frederik Spindler about the evolution of haptodonts and other early synapsids, Jan Fischer about oxygen isotope signals in Permian and Triassic freshwater shark teeth and I had a talk on osteoderm histology and the Chroniosuchia). My colleagues Ilja Kogan and Jan Fischer won the 1st poster prize with their poster entitled "The Madygen lake deposits: A unique multi-taxa kindergarten for Triassic fisches" - which is quite an achievement as normally the winner comes from the host institute of the Palges Meeting.

The image on the right shows me in front of a poster entitled "Paleontology in the German Wikipedia" [pdf].

Even though there are many private collectors and paleontology enthusisasts in Germany, Austria, and Switzerland you won't find much about "regional paleontology" in the German Wikipedia which was the reason for my colleagues and me to introduce some aspects of Wikipedian (Pop-)Sciencewriting.

The poster praised the advantages Wikipedia can have if it is reasonably incorporated in public outreach campaigns and we commented critically on the dinosaur focus which increases the already biased public image of what paleontology is about.

Madygenerpeton pustulatus: first description finally out

2010-10-28T14:57:00.000-07:00

Schoch, R. R., S. Voigt, and M. Buchwitz. 2010. A chroniosuchid from the Triassic of Kyrgyzstan and analysis of chroniosuchian relationships. Zoological Journal of the Linnean Society 160(3): 515-530. [Abstract]

Madygen trace fossil paper

2010-03-22T18:07:00.000-07:00

Voigt, S. and D. Hoppe. 2010. Mass Occurrence of Penetrative Trace Fossils in Triassic Lake Deposits (Kyrgyzstan, Central Asia). Ichnos 17:1-11. [Link]

Besides the exquisite soft body preservation of insects and tetrapods within some parts of the lacustrine succession, the Triassic Madygen lake shows a rich inventary of invertebrate trace fossils, studied by my colleague from Freiberg Sebastian Voigt.

The interesting point about these ichnofossil assemblages is that they demonstrate a certain differentiation of the lake ground in better and less well aerated zones, displaying different degrees of bioturbation and abundances of indicative ichnotaxa.

You can imagine that fresh water lake grounds only became inhabited stepwise after the conquest of land by animals, so these trace fossil assemblages mark a certain evolutionary level of lake ecosystems, otherwise rarely documented in detail from the Middle to Late Triassic.

Perception of deep time by geologists and biologists

2010-02-28T10:58:00.000-08:00

Following the Darwin Year a colloquium lecture by zoologist Prof. Wolfgang Maier from Tübingen dedicated to "Darwin and deep time" discussed Charles Darwin’s role as a geologist who (among others) introduced the concept of deep time (a term later coined for million to several billion year long time ranges in geology) to biology.

Darwin did this by translating a hierarchy of (anatomical) similarity into a tree scheme that linked organisms from successive time slices with thousands of generations separating each two slices (see the scheme from Darwin’s "Origin of Species": [link]). The time slices can be related to certain units of the geological time scale.

Deep time correspondents in stratigraphy …

The problem of imagining time ranges far outside the scale of human experience has been approached by geologists with the method and concepts of stratigraphy: Strata of rock can be interpreted as a succession of time slices. Relative ages and age differences often manifest in an amount of rock which is loosely corresponding to certain a time span if similar rockforming processes are underlying. The relationship between the duration of a process and the amount of materal it creates can be inferred from direct observation of recent systems, allowing the assignment of absolute time (in years or millions of years) to a succession of strata. Given that long-term geological processes are rarely gradual, a more reliable absolute age is provided by radiometric dating.

If you would ask a geologist how he/ she percieves deep time I suppose he/ she would explain that it becomes clear from the slowness of present-day geological processes on the one hand and from the vast amount of products of such processes on the other hand.

… and phylogenetics

The evolution of organisms yields another approximation of deep time: The passing of time manifests in the hierarchical distinctness of living systems. Seeing how slow evolution works in a human being’s life span and how much change in anatomy/ biochemistry etc. must have occurred since last common ancestor of mouse and elephant or of mouse and lemon tree, leads to another way of percieving long time spans.

Regarding a certain distinctness and species richness of a group as a product of a certain number of character changes and speciation events (which is more or less well correlated with time) was probably enhanced by the more quantitative look at phylogenetics since the introduction of cladistics and molecular methods.

When I was attending a workshop on molecular paleobiology in 2008 specialists of that field were using the expression “(addressing) deep time problems” synonymous to phylogenetics of higher systematic groups, i.e. as the study of evolutionary changes that occurred deep down in the tree of animals and other organisms – opposed to let’s say the comparative analysis of human and neanderthal genomes or the radiation of Darwin finches.

The viewpoints of paleontologists…

But how do (present-day) paleontologists percieve deep time? You would expect them to share the view of both, phylogeneticists and stratigraphers, as most of them are taught at least a bit about both fields. However, for a paleontological fieldworker who employs the study of fossils as a means to understand and describe geological processes and paleoenvironmental contexts the flow of time is much easier grasped as a series of events preserved in a succession of rocks (and not as a phylogenetic tree scheme).

On the other hand, as a consequence of the so-called paleobiological revolution, you don’t need to be a field worker to contribute to the understanding of ancient organisms. In fact many aspects of paleobiology require mere laboratory and magazine work and you can spend a lifetime on that without ever considering rocks – naturally the perspective of such a modern paleobiologist on deep time will be strictly that of a phylogeneticist.

…can lead to conflicts?

These different perceptions on deep time and evolution are probably the background why cladistics was (and still is) met with some scepticism by “old school paleontologists” (or by “Eastern Europe school paleontologists”): Instead of considering all kinds of data for phylogenetic hypothesis-making I am supposed to use merely data from the (anatomical, molecular, etc.) comparison of organisms, as if evolution does not manifest in other ways in the geological record.

One could argue that it is possible to integrate other data, i.e. stratigraphic ages and palaeobiogeographical relations, in a cladistic analysis or at least in the discussion of its results, and so assure that hypotheses from the tree perspective on evolution are tested under consideration of independent data.

The idea to use time directly as a character in a parsimony analysis with consecutive time slices as character states may be epistemically unsound, as it is problematic to justify any kind of model assumption how time is weighted with respect to anatomical characters (and implicitly would this mean a post-hoc failure if proximity in time is regarded as indicative for degree of relationship?).

An a posteriori fit to other data – e.g. looking which of the equally parsimonious morphology-only-based time-calibrated trees has shorter lineages of no record (ghost lineages) – might be a better approach, but is still hard to swallow for some people who have problems with parsimony analyses on the basis of (too) small character samples (i.e. with inherent biases due to sample size/ character poorness or ambivalence of fossils).

Madygen News 2009

2009-10-17T20:29:00.000-07:00

Expedition. This year's two month expedition to Madygen, Kyrgyzstan, ends in about a week. Rather than merely assembling more fossils the task for 2009 was to carry out further observations concerning the facies architecture and fine stratigraphy of the Madygen Formation - in fact to solve the evolution of the Madygen depositional environment throughout the time comprised by the Triassic sequence of the Madygen SW outcrop area.

Since the ways of communication between Germany and the Kyrgyz outback are difficult I didn't get much of an opportunity yet to talk to Madygen project leader Sebastian Voigt (my de facto chief who is still in the field). But from what I've heard the paleoenvironment is now well explained and some furthergoing approaches, e.g. comparing the conditions of Madygen to those of the other (few) terrestrial lagerstätten of the Triassic, are now feasible.

Symposia contributions and papers

- on the flora:

Moisan, P., H. Kerp, S. Voigt, C. Pott & M. Buchwitz (2009): Cycadophyte foliage from the Triassic Madygen Formation, SW Kyrgyzstan Central Asia. Terra Nova 2009/3:81-82. [Abstract Volume of Annual Meeting of the German Paleontological Society in Bonn] ... the respective paper is soon to come.

- on kazacharthran body and trace fossils: ... still in the review process.

- on fish:

Kogan, I., K. Schönberger, J. Fischer, S. Voigt & M. Buchwitz (2009): A nearly complete Saurichthys specimen from the Triassic of Madygen (Kyrgyzstan, Central Asia). Terra Nova 2009/3: 63-64.

A first note on this find will published at the end of 2009 in Freiberger Forschungshefte.

SVP poster on egg capsules and teeth of hybodont sharks, which have been discovered in 2008: Fischer, J., S. Voigt, M. Buchwitz & J.W. Schneider (2009): The selachian fauna from the non-marine Middle to Late Triassic Madygen Formation (Kyrgyzstan, Middle Asia): preliminary results. JVP 29 (3, suppl.): 95A-96A.

- on chroniosuchians:

Buchwitz, M. & S. Voigt (2009): Locomotion aspects of a chroniosuchid carapace. In: D. Schwarz-Wings, O. Wings & F. Sattler (eds.): 7th Annual Meeting of the European Association of Vertebrate Paleontologis - Abstract Volume. Aachen, 2009, p.14.

Buchwitz, M. & S. Voigt (2009): Phylogenetic and functional implications of the chroniosuchian osteoderm morphology. Terra Nova 2009/3: 25.

I'm trying hard to finish these manuscripts just now. The first description of the new chroniosuchid species, focussing on the skull features, is 'in press'.

- about the thing that must not be named:

Buchwitz, M., S. Voigt & J. Fischer (2009): Dorsal appendages of You-know-what reconsidered: aspects of development and the link to the evolution of filamentous integumentary structures. JVP 29 (3, suppl.): 72A.

...there is another longer manuscript putting some effort into the detailed description/documentation and a discussion of some rather modest model (... but I cannot really tell yet whether an 'accept' is feasible in the near future).

- on the depositional environment of the Lagerstätte Madygen and its tetrapod localities:

Voigt, S., M. Buchwitz, J. Fischer, P. Moisan & I. Kogan (2009): Lagerstätte Madygen - outstanding window to a continental Triassic ecosystem. JVP 29 (3, suppl.): 196A.

Buchwitz, M., S. Voigt, J. Hentschke & P. Moisan (2009): The Triassic Madygen Formation (Kyrgyzstan, Middle Asia) features a new tetrapod locality. Terra Nova 2009/3: 25-26.

...the latter poster introduces some (real) archosaur finds from 2008.

Questionnaire for Geobloggers(incl. Paleobloggers)

2009-10-04T10:02:00.000-07:00

http://geoblogs.stratigraphy.net/survey/

The organisator is my former study colleage Lutz Geißler (now M.Sc. in geology), who is at the German forefront of publicising geoscience - with his web portals geoberg.de, geonetzwerk.org, and with his postcard/ poster/ online campaign "Wir sind überall." ("We are everythere!" - referring to the role geoscience plays in daily life/ for the satisfaction of basic needs).

SVP meeting reminiscences

2009-09-30T15:30:00.000-07:00

My first SVP meeting was a bit of an eye opener for me:

Microtomography and 3D imaging, molecular paleobiology, advanced phylogenetical and biogeographical approaches, bone and tooth histology and microstructures, morphometrics, biomechanical modelling, any kind of studies on living functional/ ecological/ developmental analogues of fossil beings (actuopaleontology) - that's where the pot of gold is hidden.

... as a former geologist it gives me a certain urge to come to terms with what I should have learned about biology but only got briefly or autodidactically yet.

Apparently world is not as easy and small as it seems when you work as an isolated scholar for too long a time.

Reptile from the Petrified Forest of Chemnitz

2009-09-28T04:37:00.000-07:00

In Early Permian volcaniclastic deposits of Chemnitz (Saxony, Germany) the partial skeleton of 30-cm-long basal reptile including a complete autopodium, further parts of the limbs, the vertebral column, thorax, and a fragmentary skull have been discovered last week by excavators from the Natural History Museum of Chemnitz.

This is the first tetrapod fossil from these deposits which are otherwise famous for their in situ silified tree stems ("Petrified Forest of Chemnitz").

Symposia Summer: Are posters for kids? I daresay yes.

2009-09-11T18:09:00.000-07:00

My former room mate (a post-doc and Humboldt scholar) once said that poster presentations rapidly lose their appeal once you have reached the age of speaking. And perhaps he was right after all.

Inlcuding this year's SVP meeting contributions I made 10 posters and was co-~~painter~~author of further 6 during the last three years (about two thirds about paleontology and one third on structural geology). That's enough to paper the walls of my of and my neighbour's lab room, but what did I get apart from that?

Flooding of the publication list? - Yes, but 20 abstracts = 1 peer-reviewed paper. To get something published cheeply should surely not be the point of postermaking - also considering the overall time you are investing for a mere halfpage of printed text.

Becoming a whiz in vector graphics? - Perhaps, but this is also part of normal publishing, lecture-preparation and thesis-writing, so you would have learned that anyway...

Feedback from experts? Negligible. Sometimes you are lucky and the right people are present and really interested in what you have done - but if they are not and yours is one of 50 posters displayed don't be too optimistic. Some people are so frustrated about the (probable) lack of response that they have their posters pinned up by an oral presenter from their own faculty and save the travel costs.

Dialogue with my former supervisor about a poster of mine:
- "Luckily I can give this to Maria. Symposia are such a waste of time!"
- "Obviously, you don't have yet understood what this part of science is about..."
- "Of course, I know about the importance of communicating your science and stuff... I was only teasing." (Afterwards pretending it was only irony, but meaning every word I said at first.)

I forgot something important: the winning of the poster prize! You can try. You need high-resolution colour fotos, high quality drawings, mirror finish paper, a sense for symmetry and for the golden section, and a vanilla ice topic (like dinosaurs, trilobites, Cambrian explosion, human origins).

And afterwards you can fancy yourself as the king of the ~~symposium junior scientists~~ layouters. Three cheers for the PP winner!

Why an oral presentation is better

Preparing an oral presentation is more time-consuming than making a poster: you have not only to put figures on a (rather patient) sheet of paper and do some write-around. Giving a talk you are really forced to make sense of your premisses, methods, data, results, conclusions and arrange everything in a sequence (only one dimension - time; a poster has two dimensions so you can illustrate complex interrelationships more easily and thus be more confuse without notice).

All these aspects help you directly with your scientific work: A well-structured presentation can easily make a well-structured publication and vice versa. And if there is a catch or lapse in reasoning you may become aware of it in the course of trying to explain your model to others.

With an oral presentation you get a real audience: Even if no one is interested in your topic common politeness makes them stay still and gives you the power to waste 15 minutes of the life time of 50 or 100 or 200 listeners. What a feeling of might!

If you are provocative you can even stir up a reaction. Compare posters and talks to potted plants and dogs. A dog/presenter is barking at you if he wants attention and thus you feel pushed to show him his place, the poster/ potted plant is simply hanging/ standing around and withers...

So give a talk if you have the guts!

Fieldwork photo of the week

2009-08-12T14:35:00.000-07:00

Some parts of the Madygen succession are particularly rich in plant remains inluding calamite stems accumulated in thin, sometimes coaly siltstone layers.

Contributing to Wikipedia as a paleontologist/ geoscientist

2009-08-01T20:00:00.000-07:00

There was a time when Wikipedia articles on palaeobiological and geoscientific topics where almost exclusively abysmal, including unreferrenced children's-book-like fossil animal portrayals 30 years behind the state-of-the-art.

That there has been a change during the last years, is more or less the consequence of the infusion of expert or semi-expert knowledge. Compare this and this version of the English Wikipedia article on a famous fossil taxon and you may acknowledge that a 5 year riping process can result in a nice and relatively up-to-date encyclopedia article.

Scepticism from the scientific community had different causes:

(1) unreliability as a data source/ lack of references - these problems were mostly solved when the community of WP writers established higher standards and agreed on that all major points made by an article have to be supported by independent sources.

(2) WP-related plagiarism by students. I suppose this is merely a problem of teaching youngsters the difference between right/honest and wrong/inhonest use of source texts and nothing Wikipedia can be blamed for.

(3) potential influence by people with a special agenda. Mostly neutralized by the overload of sensible/ unbiased Wikipedia workers. In most cases the WP community has enough background knowledge - so that unsupported/biased statements are recognized and rejected/presented in a neutral way.

There is also the question of utility, especially from the expert's point of view...

Why writing WP articles can be a worthwhile operation...

(1) Your contribution will be read. Search engines mostly place Wikipedia articles very high on the list. Anyone searching your article's lemma will find your text and use it. Thus you will be the provider of primary insight into a specific scientific topic.

Your article may be helpful even for serious research - namely for scientists of related fields searching for the explanation of a term (and references to further technical literature/ online sources).

(2) You can bring rarely publicised aspects of your science to public awareness by the choice of the topics you are writing about. By creating a featured article on a rare species of ammonoids you can direct the focus of paleo-enthusiasts to an otherwise neglected field (you gain more publicity for what is really at the heart of your interest).

(3) Sometimes it is a good excercise to recount for a non-specialist audience what appeared plausible in the internal discourse among scientists of your field. You may find that some concepts are hard to explain (and perhaps don't make much sense when in the cold light of day...).

This list could be could be continued.

Hindrances for new expert authors?

Frequent misunderstandings about the Wikipedia project are listed under "What Wikipedia is not" - you should read this to prevent later disappointments.

There are some Wiki formats - mostly as easy or easier to handle than HTML codes - and you are facing a growing body of rules and conventions. A recipe is to copy and paste the style/format features of an existing article code and to fill in your new content.

Don't argue too much about styles and formats with established Wikipedia users. Your primary aim as a specialist should be to provide up-to-date information, scientific background and overview knowledge, and corrections on misconceptions/ misunderstandings which often arise from the popularization of science.

If you out yourself as an expert you will find that amateurs among the experienced Wikipedia users will give you much support at the beginning and back you up in discussions (which can arise if you are working on controversial topics).

My own Wikipedia experience

I had my first edits in the German Wikipedia in 2005 when I was still an undergrad. If English is not your mother tongue you may think about editing articles in your own language WP, but mostly in the en:WP there is more substance to start with.

In any case you will find that much work is to be done and that you have to be selective with your engagement. Look at the points that you believe are most important and easily done. If you have done a literature search for your professional work you may use some of the data again for a WP article. If you are a PhD student, be aware of the Wikipedia procrastination potential!

EAVP Meeting 2009 in Berlin, Germany

2009-07-25T05:20:00.000-07:00

This week the European Associatuon of Vertebrate Paleontologists had its 7th annual meeting at the Humboldt University of Berlin Museum of Natural History, organized by Daniela Schwarz-Wings and her team.

Between Tuesday and Thursday about 34 oral presentations were held and 22 posters were displayed. Sorted systematically:

reptiles: 19.5 oral presentations (dinosaurs: 11) + 10.5 (7) posters
synapsids: 8.5 (mammals: 7) + 6.5 (6)
fish/ sharks: 3 + 3.5
anamniote tetrapods: 3 + 1.5

Apparently the EAVP is mostly a paleoherpetological society.

The two field trips organized for Friday covered the Rüdersdorf Muschelkalk Quarry (which yielded Nothosaurus, Placodus and others critters of the marine Middle Triassic) and the Pleistocene Rixdorf horizon of Niederlehme to the SW of Berlin.

Christian A. Meyer from Basel became new president of the EAVP, he takes the office over from Eric Buffetaut who is new editor-in-chief of the society's online-only journal Oryctos. Next year the meeting will be held in Aix-en-Provence in southern France, Greece is planned for 2011.

Chroniosuchians and stay in Moscow

2009-06-28T17:03:00.000-07:00

To resolve the riddle: The bonified eyeball from the last post represents a a ball-shaped intercentrum of a chroniosuchid from the Permian of Russia.

In chroniosuchian reptiliomorphs the intercentra (white arrows) are interlocked with the amphicoelous pleurocentra in a ball-and-socket-like fashion. The image on the left shows some section of a Chroniosuchus vertebral column in ventral view. Intercentra become bony balls only in the adult individuals - not fully bonified in sub-adults and juveniles they are preserved with a crescent, disk-like or ellipsoidal shape.

Also, the fusion of the neural arch with the pleurocentrum - a feature otherwise characteristic for "higher reptiliomorphs" such as seymouriamorphs and diadectomorphs - is only completed in the course of ontogenesis (so that you can find suture lines in the subadult individuals).

Moscow: Paleontological Institute and Museum of the Russian Academy of Sciences (PIN)

The paleo-style PIN building has a castle-like rectangular shape with an inner courtyard featuring life-size sculptures of fossil critters from Russia and areas of the former Soviet Union. The exhibition has almost everything you wish for as a vertebrate enthusiast (here depicted: the two-story dinosaur hall). Rich in type specimens the collection is essential for some and important for many studies - so earlier or later many of the fossil vertebrate people spend some time there.

Concering the Chroniosuchia: With the exception of bystrowianid chroniosuchian remains from Kupferzell, Germany (Witzmann et al. 2008) and China (Young 1979) and some rather questionable Chinese chroniosuchid chroniosuchians (Li & Cheng 1999), all yet described Permian and Triassic chroniosuchian taxa come from the European part of Russia and are mostly archived in the PIN. I am thankful to Valery Golubev who helped me a lot during my week of stay when I was studying the type materials and to Jury Gubin who nicely put up with me in his room.

Some literature on chroniosuchians

Here considered: titles also available in English (plus the Chinese ones mentioned above).

Golubev, V. K. (1998). "Narrow-armored Chroniosuchians (Amphibia, Anthracosauromorpha) from the Late Permian of Eastern Europe." Paleontologicheskij Zhurnal 1998(3): 64- 73. [Russian, English]

Golubev, V. K. (1998). "Revision of the Late Permian chroniosuchians (Amphibia, Anthracosauromorpha) from Eastern Europe." Paleontologicheskij Zhurnal 1998(4): 68- 77. [Russian, English]

Golubev, V. K. (1999). "A new narrow-armored chroniosuchian (Amphibia, Anthracosauromorpha) from the Late Permian of the East Europe." Paleontologicheskij Zhurnal 1999(2): 43- 50. [Russian, English]

Li, J., Cheng Z. (1999). " New anthracosaur and temnospondyl amphibians from Gansu, China." Vertebrata PalAsiatica 37(3): 234- 247. [Chinese with English abstract]

Novikov, I. V., M.A. Shishkin (2000). "Triassic chroniosuchians (Amphibia, Anthracosauromorpha) and the evolution of the trunk dermal ossifications in the bystrowianids." Paleontological Journal 34(supplement): S165- S178. [English]

Novikov, I. V., M.A. Shishkin, V.K. Golubev (2000). Permian and Triassic anthracosaurs from Eastern Europe. The Age of Dinosaurs in Russia and Mongolia. M. A. S. M.J. Benton, D.M. Unwin, E.N. Kurochkin. Cambridge, Cambridge University Press: 60- 70. [English]

Witzmann, F., R.R. Schoch, M.W. Maisch (2008). "A relic basal tetrapod from the Middle Triassic of Germany." Naturwissenschaften 95(1): 67- 72. [English]

Young, C. C. (1979). "A new Late Permian fauna from Jiyuan, Honan." Vertebrata Palasiatica 17: 99- 113. [Chinese with English abstract]

Bonified eyeball

2009-06-24T04:12:00.000-07:00

Or what the hell is this?

Lineage concept vs cladistics in continental biostratigraphy

2009-05-26T01:40:00.000-07:00

The white hair of my chief Ph.D. supervisor is to some degree explained by his livelong efforts to get a grip on Carboniferous to Permian continental biostratigraphy - trying out different groups such as cockcroaches, conchostracans, freshwater sharks, and amphibians.

One of the underlying concepts which I suppose I will always find hard to believe is the idea of searching for and finding so-called lineages, i.e. series of species occurring subsequently in the stratigraphic record which show stepwisely distinct anatomies because each species has descended from the respective next-oldest species.

Of course every species has an ancestor and many have descendants but how can I define them from the fossil record? Is there not the typical problem of epistemic vagueness of the ancestor in any kind of phylogeny (e.g. discussed by Wolf-Ernst Reif in some of his many theoretical papers on cladistics in paleontology)?

Searching for lineages leads to a fallacy?

The idea that whithin a continental sedimentary succession a certain species occurring deeper than a related species should be regarded as the ancestor of the latter - unless disproven - always reminded of a type of logical fallacy called post hoc ergo procter hoc: "B occurred later than A, therefore A must be the reason for B." In terms of imposing the lineage concept: "Species B occurred subsequent to species A, therefore A must be the ancestor of B."

If a multiple- and irregularly branched bush is a good analogon to how evolution works I daresay the idea of a biostratigrapher to pick up the isolated fragements of branches (i.e. fossils) and glue them together in a few long continuous branches results in a bad model of the bush.

The problems occur after I have established a biostratigraphic zonation concept on the basis of what I think is a lineage: Someone working on the same material puts the species of my 'lineage' into a cladistic analysis and finds that there is almost no concordance between the appearance date of a species and its likely phylogenetic position.

If I do agree that similarities/ dissimilarities in morphology, histology, behavior, etc. should form the basis of a classification and consider the data basis of the phylogenetic analysis as sufficient I will have to admit that my scheme has been proven wrong. Or else if I suppose that the data are not sufficient and I myself cannot add more then I will have to concede that my scheme is at least no more valid than the alternative.

Proving microevolution depends on the sufficiency of "population" samples?

Im not saying that it is impossible to find arguments in favor of an ancestor-descendant relationship: Imagine I have large enough sample of specimens of the supposedly related species A, B, and C from three successive horizons. For A, B, C the empiric distributions of morphological parameters can be compared:
If the mean value & variance for A is not signficantly distinct from the mean and variance of B and
if the mean value & variance for B is not signficantly distinct from the mean and variance of C
but given a significant difference in the mean values/ variances of A and C,
I could infer that from A to C microevolution took place...
...but do we have such samples, let's say for tetrapods?

An example: Amphibian Biostratigraphy

These problems have been discussed for the amphibian biostratigraphy of the European Permocarboniferous as developed by Werneburg and Schneider and applied for various amphibian occurrences, see for example:

R. Werneburg & J.W. Schneider, 2006, Amphibian biostratigraphy of the European Permo-Carboniferous. In: S.G. Lucas, G. Cassinis and J.W. Schneider, Editors, Non-Marine Permian Biostratigraphy and Biochronology: Geological Society of London, Special Publications 265 (2006), pp. 201–215. [Link]

R. Werneburg, A. Ronchi, and J.W. Schneider, 2007, The Early Permian Branchiosaurids (Amphibia) of Sardinia (Italy): Systematic Palaeontology, Palaeoecology, Biostratigraphy and Palaeobiogeographic Problems. Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 252, Issues 3-4, 3 September 2007, Pages 383-404 [Link]

The zonation scheme and proposed lineages have been criticized by Steyer (2004) as being a stratophenetic rather than a true phylogenetic approach considering the criteria how the authors relate different species:

J. S. Steyer, 2004, Phylogenetic or stratophenetic systematics? - Comment of R. Werneburg: The branchiosaurid amphibians from the Lower Permian of Buxières-les-Mines, Bourbon l’Archambault Basin (Allier, France) and their biostratigraphic significance. Bull. Soc. géol. France, 2004, 175 (4), 423-425
[Link]

Another particular problem is that amphibians are known to be abundantly subject to heterochronous evolution - evolutionary shifts in the ontogenesis, in particular, neoteny, is a common phenomen and can obscure characteristic features.

A recent analysis by Schoch & Milner (2008) on branchiosaurids, a group of neotenic small dissorophoid temnospondylians which is often considered for biostratigraphy, features a cladistic approach and proposes a scenario, related to which nodes of the tree neoteny/ life style changes occurred:

R.R. Schoch & A.R. Milner, 2008, The intrarelationships and evolutionary history of the temnospondyl family Branchiosauridae. Journal of Systematic Palaeontology (2008), 6 : 409-431 [link]

While the relationship of Branchiosaurus forming the outgroup of major clades (Melanerpeton-clade, Apateon-clade) is correspondent to the order of occurrences in the stratigraphic record, certain long ghost lineages occur - in particular the interpretation of Apateon gracilis/Melanerpeton gracile shows a mismatch between the cladistic approach of Schoch & Milner and the scheme of Werneburg & Schneider. This divergence is also the consequence of conflicting interpretations of the gracil(e/is) material, however, it demonstrates the potential for stratigraphic misinterpretation:

If I believe that a species forms the end member of a lineage because it is the youngest in certain sedimentary sequences I may underestimate the species' stratigraphic range - unlike the cladistic analysis which (if well-founded) would imply a deep divergence suggesting that some of the earlier record of the species is missing.

Decoupling (continental) biostratigraphic zonation from the lineage concept

Assuming that evolution works rather bush-like than lineage-like, I dont' see why we can't keep a biostratigraphic zonation even in the case of sparse continental records. I still can associate a series of morphologically defined taxa with a certain stratigraphic range and spatial distribution - until the concept has been shown not to be adequate (or not outside a more narrowly defined spatiotemporal window).

Whether it is a lineage-like relationship of species or another factor (related to geography, climate, ecology or else) that makes biostratigraphy work is a question which might be solved only in some cases.

PALHERP Bonn 2009

2009-05-14T23:00:00.000-07:00

The Meeting of the German Paleoherpetologists was launched in 1997 as an act of rebellion against the old mammal establishment which ruled the regular vertebrate workshops of the German Paleontological Society. A particular aspect of the Palherp is the relaxed atmosphere giving students the chance to present ideas and results without unfair senior criticism.

Last weekend the 13th Palherp meeting was held in Bonn. As the Steinmann Institute of Bonn University houses the German Research Foundation Unit on Sauropod Biology you can call it one of centres of paleoherpetology in Germany. Given the focus of the Bonn working group many of this year's presentations covered dinosaurs and/or bone histology.

Saturday: Martin Sander's keynote lecture on sauropod biology was followed by presentations on sauropodlet longbone histology, on rib histology and sauropod reproduction strategies.

The lower tetrapod session covered chroniosuchians, a pelycosaur jaw fragment as the earliest German amniote find, parareptiles and a basal diapsid.

In the afternoon a presentation on didactyle theropod footprints from the Oberkirchen Sandstone and a discussion of arguments/ phylogenetic analyses in favour of convergent flight origins in the Eumaniraptora followed. Furthermore a talk on finds from the Lower Muschelkalk of Winterwijk. H. Haubold discussed problems related to the continental P/T mass extinction event if it is taken as a dogma.

Sunday talks included the introduction of a new basal sauropod (from Niger), dinosaur palaeopathology, tooth morphology, isotope palaeontology, and 19th century history of dinosaur science.

Fieldwork Photo of the Week

2009-03-18T11:38:00.000-07:00

Madygen river oasis. Close to the point where the river cuts through a Paleozoic limestone massif (on the left), forming a deep gorge.

Fieldwork Photo of the Week

2009-02-28T14:21:00.000-08:00

Badlands of the SW outcrop area (Urochishche Madygen). Reddish colours mark the "Variegated Member" of the Madygen Formation. In the distance: tree tops of the Madygen river oasis.

Fieldwork Photo of the Week

2009-02-19T13:54:00.000-08:00

Colourful Jurassic strata. Who can see the unconformity?

Constructivist geoscience (II)

2009-02-17T18:12:00.000-08:00

As a natural scientist you are disposed to believe that there is something on the outside of your consciousness, and also, that you as a human being have suitable means to investigate those things.

And there is the theory of critical rationalism and the praxis of how geoscience (and palaeobiology) is really done.

So what about the chronic underdeterminedness of geoscientific (and paleobiological?) models: Is the remaining uncertainty large enough to consider much of the geoscientific knowledge as mere constructs which are (forseeably) bad descriptions of real things?

The following list of sources of uncertainty and of other problematic points is without order, representing a collection of thoughts I had during one of those late night train journeys:

(1) Uncertainty from the misunderstanding of recently active complex processes (e.g. sediment transport by a river) used as model systems for ancient processes.

(2) Uncertainty from a lack of knowledge about the longterm consequences of currently active processes.

(3) Anactualistic processes (e.g. on Hadean earth; recovery after a meteorite impact).

(4) Selectivity of geological records and the variety of factors by which it can be governed.

(5) Equivocality of deeper earth investigation methods (geophysics, "1D" outcrops from drillings).

(6) Problems arguably associated with the "descriptive tradition of geoscience", which passes along varying ideas about the necessary exactness. There can be a certain disregard for matters of decision making, the question of how to choose a favourite hypothesis, the distinction between noise and information relevant for a problem.

(7) Plurality of fieldwork procedures [and other aspects of methodology], i.e. documentation methods in the field and the decision makings/ usuals paths of inference involved. Enhanced by national/ language boundaries - there can be different schools, sometimes failing to communicate.

(8) Choice of model systems: Due to the complexity of the matter we are choosing well understood model systems, but the comparability is overestimated in the specific case.

(9) Overuse of a canon of "inherited" procedures, which lead to systematic misunderstandings or put constraints on thinking (e.g. the drawing of sedimentary logs).

(10) Metamodels and metatheories (e.g. global palaeoclimate models, supertrees) may be particular problematic in geology/palaeontology as historical sciences. There may be so various data and multiple steps of inferences that circularities are hard to avoid and/or the question is, of how much value the insight from the model is.

(11) Bad integration of data in multidisciplinary approaches, if the model assumptions on which the integration is based are not well considered.

(12) Overinterpretation as a notorious phenomenon in geoscience, coming from the chronic paucity of data, the community's failure of encouraging modest/ honest claims.

(13) Unsystematic or right-out defective handling of temporarily or principially not-available data. (Hypothesis hinges to a considerable degree on the missing data - though you as the inventor are saying the solution of the problem is only a matter of effort.)

(14) As in other sciences: the dealing with falsifying data. As your object is so complex, you as geoscientist may always find an exception demonstrating that you are not (so) wrong.

(15) Underuse of quantitative approaches, another relic from earlier times of geosciencemaking.

(16) Changing accessibility of important outcrop areas (but also archives) limits falsifiability of hypotheses.

(17) Misinterpretations from reducing/ enlarging the dimensionality of a problem in an inference step (e.g. reconstructing a time series of 3D models from a number of 1D sedimentary logs). Not always considered: There is not necessarily a proportionality between the time span of a process and the volume of "waste" it creates or deletes.

(18) Downscaling, if done without reflection/ definition of the way of doing, can reduce the reproducability/ comparability.

(19) Thinking in cyclicities and the tendency to infer cyclic processes although their support is poor.

(20) Misconception about what the data are and where the interpretation begins. One might think this is only a beginner's mistake in geoscience - however, it may happen as well on a higher level if you have multiple stages of inference.

(21) Thinking in categories as though they represent something natural which is not defined by the observer (e.g. genus, family in biological systematics; stage, era in chronstratigraphy).

So, look critically at your own models in geoscience (and paleobiology). Are they well constructed?

Permotriassic entomofaunal change + the Madygen

2009-02-13T18:25:00.000-08:00

Dmitry E. Shcherbakov from Moscow is one of the paleobiologists studying the very group of beings for which Madygen really is a lagerstätte: insects.

Some of his 2008 papers in the Moscovian Paleontological Journal and Alavesia, a relatively new journal for fossil insects, can be found as .pdfs on the library page of the International Palaeoentomological Society (IPS).

Shcherbakov, D.E. 2008. Insect recovery after the Permian/Triassic crisis. Alavesia 2: 125-131. [pdf]

Shcherbakov, D.E. 2008. On Permian and Triassic insect faunas in relation to biogeography and the Permian–Triassic crisis. Paleontological Journal 42 (1): 15-31. [pdf]

The Alavesia paper outlines a three phase development of Triassic entomofaunas, beginning with
(I) a low-diversity episod of P/T recovery dominated by Paleozoic insect groups, followed by
(II) a summit phase with typical Triassic taxa in the Anisian-Carnian, and, with a decline in diversity, ending in
(III) a phase dominated by Late Mesozoic elements, especially featuring new aquatic insect groups.
Shcherbakov suggests, that each of the transitions began in the humid low latitudes and occurred later in the higher latitudes, i.e. the boundaries between those three stages are diachronous.

In the Paleontological Journal paper Dmitry Shcherbakov looks at the insect diversity of Late Carboniferous to Triassic localities, counting the proven occurrences of insect families per stage ('stage' as a chronostratigraphic unit). He illustrates the change in aquatic/ terrestrial, phytophages/ predators, modern/ ancient groups and explains the ecological, evolutionary, and biogeographic background of diversity fluctuations.

Shcherbakov, D.E. 2008. Madygen, Triassic Lagerstätte number one, before and after Sharov. Alavesia 2: 113-124.[pdf]

This review paper begins with a recount of the research history of the Madygen Formation as a Triassic fossil locality, beginning with the geological fieldwork in the 1930s (by Kochnev) which led to the first finds of a fossil flora, classified as Triassic, and to the introduction of the Madygen strata as a separate stratigraphic unit.

In detail the role of paleoentomologist Alexander G. Sharov is recognized, who lead five field expeditions between 1962 and 1966 to a fossiliferous point in the northern Madygen outcrop area (Dzhailoucho). These campaigns turned out as the most successful with regard to the number of recovered insect specimens and other fossils. The historical part is followed by a short overview of the flora and non-insect fauna.

The main part is a synopsis of the particular insect fauna of Madygen. Besides the exquisite state of preservation, several figures illustrate why Madygen really is a lagerstätte: Members of twenty insect orders and 96 out of 106 insect families known from the Ladinian/Carnian have been reported from the Madygen Formation.

In this order beetles, cockcroaches, and homopterans represent the most abundant groups. Among rarer groups are certain specialities, such as the most diverse assemblage of titanopterans. Modern insect orders are represented by several groups of early dipterans and the earliest hymenopterans (belonging to the group of sawflies).

Ballad

2009-02-12T15:28:00.000-08:00

In memory of Charles R. Darwin (1809-1882)

My fish is sad and lonely
Striving for arms to embrace only
O Lamarck, the flesh is weak!
The fins just stay-
Despair 'n' dismay.

See generations later
Arms had but the best wade-through raider.
Fish feelings selection not passed.
They ebbed away-
Despair 'n' dismay.

Nothing but comprehension
Lies in Darwin's more stately mansion
World tells no moral'ty tale.
No more to say-
Despair 'n' dismay.

Fieldwork Photo of the Week

2009-02-02T05:03:00.000-08:00

In the back you can see a tectonic contact: Massive limestones are thrusted over some less competent schist units and/or Madygen sediments. Thanks to Juliane for that photo.

Triassic critters: Freshwater sharks

2009-01-23T20:00:00.000-08:00

Lakes and rivers of the younger Paleozoic and as well in the Triassic could not only house tetrapod and bony fish vertebrate dwellers but also selachian predators, in particular the Xenacanthida, well known for their characteristic neck spines, and the Hybodontiformes, which display a pair of lateral head spines and characteristic fin spines. The latter are distinct from those of the Acanthodii (popularly also referred to as "spiny sharks"), a group of basal vertebrates that ocurred in freshwater environments as well, but became extinct before the beginning of the Triassic.

Complete shark specimens are seldom recorded, the same is true for complex finds comprising a couple of skeletal elements from the same individual - taxonomists often have to deal with assemblages of individual scales, spines, and teeth and systematics heavily relies on tooth characteristics (e.g. Schneider 1988 for the Xenacanthida, Rees 2008 for hybodont sharks).

Like the recent bullhead sharks (Heterodontus) at least some of the Carboniferous to Triassic freshwater sharks were oviparous - different types of spiral egg capsules not quite unlike those capsules of Heterodontus occur in different types of freshwater environments, e.g. marginal lake sediments or low-energy river banks; often they appear unrelated to skeletal remains. This has been interpreted as being indicative for a separation between the actual habitats of the sharks and their spawning grounds (about the facial aspects: see Schneider & Reichel 1989). To what extent the occurrence of xenacanth and hybodont sharks in freshwater deposits is indicative for a marine influence is currently a matter of debate.

In the first descriptions of the 19th century fossil egg capsules were misinterpreted as cone-like fructifications of some kind of plant. This was due to the rhomboidal pattern the egg capsule impressions often display as consequence of taphonomic flattening (and the consequent overlap of the spiral patterns on the front and back sides). Two types of shark egg capsules have been recovered from the Madygen Formation during fieldwork in 2007 (Fischer et al. 2007) - more on that later.

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Jan Fischer, featured in the last FPhotW, who is working on the Madygen chrondrichthyans (as soon as they appear) and isotope paleontology of shark teeth/spines, is thanked here for supplying me with literature. (Hopefully I can convince Jan to write a guest contribution).

Refs:

Synoptical papers:
Maisey, J.G. (1982): The Anatomy and Interrelationships of Mesozoic Hybodont Sharks. - American Museum Novitates 2724: 1- 48; New York.

Schneider, J. W. & Zajic, J. (1994): [Xenacanths (Pisces, Chondrichthyes) of the middle European Upper Carboniferous and Permian - revision of the originals of GOLDFUSS 1847, BEYRICH 1848, KNER 1867 and FRITSCH 1879-1890.] - Freiberger Forschungshefte, C 452: 101-151; Leipzig.

On tooth systematics:
Schneider, J.W. (1988): [Basics of the morphogeny, taxonomy, and biostratigraphy of isolated xenacanth teeth (Elasmobranchii)]. - Freiberger Forschungshefte, C 419: 71- 80; Leipzig.

Rees (2008): Interrelationships of Mesozoic hybodont sharks as
indicated by dental morphology – preliminary results. - Acta Geologica Polonica 58 (2): 217-221.

On egg capsules:
Schneider, J.W. & Reichel, W. (1989): [Chondrichthyan egg capsules from the Rotliegend (Lower Permian) of Middle Europe - conclusions regarding the palaeobiogeography of palaeozoic freshwater sharks.] - Freiberger Forschungshefte, C 436: 58- 69; Leipzig.

Fischer, J., Voigt, S. & Buchwitz, M. (2007):
First elasmobranch egg capsules from freshwater lake deposits of the Madygen Formation (Middle to Late Triassic, Kyrgyzstan, Central Asia). - Paläontologie, Stratigraphie, Fazies (15), Freiberger Forschungshefte, C 524: 41-46; Freiberg.

Fieldwork Photo of The Week

2009-01-21T02:07:00.000-08:00

Morning time at the digging site: Having contemplated the vast landscape bare of human presence but sprenkled with the litter of a forgotten civilization graduate student Jan Fischer decides on the right moment for starting his daily business of not moving to many a rock at once and feigning the impression of having survived another day in this vale of tears only at the close of livelong fatigue and exhaustion...

Fieldwork Photo of the Week

2009-01-07T17:57:00.000-08:00

See the spy in the back? Some Kyrgyz aborigines can't help being distrustful...

I'm thankful to Juliane Hentschke who safed us these moments and a number of bones.

Tectonics & Paleo (4):The world of CPOs and ODFs

2009-01-03T01:43:00.000-08:00

Materials in geoscience and biology are often not isotropic - their properties, such as conductivity, soundwave velocity, and shear strength, vary with direction.

The reason can be that they are crystalline - if so, the orientation of the crystal lettice of (one, a few, or) many individual crystal grains has an influence on the properties of the compound material. The individual crystal lettice orientations can be at random or their can be a preferred orientation.

A whole branch of mineralogy and material science deals with the analysis of materials which show crystal preferred orientations (CPOs).

From Tectonics...

Structural geologists, who are dealing with microscopic phenomena of tectonic deformation, use mineral textures of rocks, i.e. crystal preferred orientations of the rockforming minerals, as indicators of tectonic movement and deformational regimes (temperature, pressure conditions; deformation rate).

The so-called Orientation Distribution Density Function (ODF) describes how the crystal axes of mineral grains in a sample are oriented relative to an outer coordinate system (e.g. geographic XYZ coordinates). From the ODF, usely depicted as a couple of stereographic density plots (e.g. plots for the crystal a-axis, b-axis and c-axis orientations) the direction and sense of shearing of a rock can be inferred.

...to Paleontology

Not only tectonic forces are governing the crystalline properties of natural materials. In a similiar way the (often monomineralic) mineralized tissues of organisms are underlying specific biological formation conditions - the different layers of a skeleton can show rather perfect CPOs.

Crystal orientations in mineralized tissue are, of course, not defined relative to a geographic coordinate system but to the anatomic directions (or the axis of accretionary growth) of the animal as a reference system.

Coming from the tectonical side I was participating in a workshop on "Textures & Microstructures in Geosciences" in 2005: I was really surprised that there is an application of texture analysis in palaeontology and that some people are really doing it.

Methodology

You can do either single grain measurements or methods integrating all orientations of crystal grains in a certain volume of the sample.

U-stage and EBSD are involving single grain measurements of a thin section: For each grain in a certain raster the individual crystal orientation is determined - either by its optical properties using the universal stage (this old-fashioned manual method is rather time-consuming) or by the way how electrons from an electron microbeam are backscattered on a detection screen (Electron Backscatter Diffraction, EBSD). The detected Kikuchi line patterns are indicative for how an individual crystal is oriented (they can be interpreted automatically). What you get in both approaches is not only an ODF but also a crystal orientation map of your thin section.

XRD, Neutron Diffraction. In these methods an X-ray or neutron beam is used to measure a larger volume of a sample comprising several crystals, thereby neutron radiation can penetrate even larger samples completely while the X-ray has a relatively low depth of penetration. From the detected line sprectra pole figures, representing the distributions of certain crystal lettice plane orientations can be derived (from which in turn the ODF of all the crystals in the measured sample volume can be deduced).

Examples from Paleontology

Chateigner, D., Hedegaard, C. & Wenk, H.-R. (2000): Mollusc shell microstructures and crystallographic textures. - Journal of Structural Geology 22: 1723-1735.

The authors employ X-ray diffraction measurements and demonstrate thate the microstructures and crystallographic textures of aragonite layers of species from different mollusc taxa including bivalves, cephalopods, gastropods and monoplacophorans are highly specific and contain a phylogenetic signal: closer relatives are more similar in their shell's crystal orientations.

Pyzalla, A.R., Sander, P.M., Hansen, A., Ferreyo, R., Yi, S.-B., Stempniewicz, M. & Brokmeier, H.-G. (2006): Texture analysis of Sauropod bones from Tendaguru. - Material Science and Engineering A 437: 2-9.

This neutron diffraction approach addresses the question whether the apatite crystallite textures in adolescent and adult Brachiosaurus long bones show some signal indicative for specialized crystal orientations which can be attributed to the giant growth of sauropod dinosaurs. However, comparing their results to the measurements of turkey and other dinosaur long bones they found no significant difference in texture strength or in the predominant direction of fibres.

Prospects

Given the elaborateness of most approaches, measurements of crystallographic textures are rarely used in paleontology - I suppose this will change if it turns out that the analysis of the crystal orientations can provide substantial information which is not obtained from the usual analysis of skeletal histology and microstructures.

Happy Darwin Year!

2009-01-01T17:47:00.000-08:00

Coming to us in 2009: festivities and colloquia celebrating the 200th birthday of Charles Darwin and the 150th anniversary of his grand oeuvre

On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life,

which was "introducing sense into biology" (badly corrupted from the Ernst Mayr quote).

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Looking back a palaeoherpetologist would call 2008 the year of the turtle:

With the descriptions of Odontochelys and Chinlechelys and some further contributions (a list is provided by N. Gardner) the origins of turtles were greatly enlightened.

This topic was variously covered by the pal(a)eo and evo blogs – see for example here and here (Bill Parker's Chinleana) or here and here (Adam Yates' Dracovenator blog).

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BTW: How many recent On-papers do you know?

What is the right occasion to start a contribution with 'on'? Did you ever think about it ... to me such a beginning suggests a long-winded reflection of/ a comment on sth. rather than focusing on the presentation of new data.

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The Twelve Days of (Paleo) Christmas are not yet over - you are still welcome to participate in the poll. >>>>>

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I support Scientific Triassicism! An initiative by Neil from Microecos. What do you think: Is 'Triassic Science' or 'Triassology' a sexier term?

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(How long one week and a half can be: I forgot how to compose a text, that's why this post is only a list of notes.)

Fieldwork Photo of the Week

2008-12-17T09:18:00.000-08:00

Excursion group 2008 and Madygen badlands, close to the boundary between "Variegated Member" (T3) and "Upper Graycolored Member" (T4) of the Madygen Formation (subdivision of Dobruskina 1995).
The transitional zone includes sandstone horizons with large-scale x beds.

Madygen: Recent contributions to symposia

2008-12-09T08:34:00.000-08:00

12th International Palynological Congress, Bonn 2008:

Philippe Moisan, Hans Kerp, Sebastian Voigt, Benjamin Bomfleur: The fossil flora of the Madygen Formation from the Middle to Upper Triassic, Kyrgyzstan, Central Asia. Terra Nostra 2008/2: 194

Abstract. The Middle to Late Triassic Madygen Formation (Kyrgyzstan, Central Asia) is a unique fossil lagerstaette for Early Mesozoic insect remains and small reptiles with soft-tissue preservation. Plant fossils from these deposits from are known since the 1930s and constitute one of the richest and most diverse Triassic floras of Eurasia. However, they received very little attention to date and their studies have to date been based on macromorphological features only. We present the first record of epidermal features of this diverse Triassic flora based on recently recovered fossil plant material. Many of the Madygen plant fossils show a highly remarkable preservation. Due to its very fine grain-size, the embedding sediment has often formed a natural cast of the epidermal cell pattern. Such epidermal features allow detailed systematic descriptions as well as palaeoecological interpretations. This fossil flora is dominated by pteridosperms, ginkgophytes, and sphenophytes. In addition, algae, mosses, lycophytes and ferns occur and many are new for this fossil flora. The high abundance of fructifications is of particular interest. Another important aspect of the Madygen flora is that many gymnosperm leaves show evidence for plant-insect interactions (e.g. margin feeding, oviposition, mining traces). The supposed Middle to Late Triassic age of the flora coincides with one of the most important herbivore expansions in the fossil record. However, while this phenomenon has been recognised in the Middle and Upper Triassic of the USA, Western Europe, and South Africa, no data are available from coeval Central Asian sequences. The on-going study aims to provide a revised systematic description of the plants, including epidermal features to characterise the palaeoecosystem of the Madygen lagerstaette in more detail, and to contribute to a better understanding of the evolution of plant-animal interactions during the Early Mesozoic.

Ichnia, Cracow 2008:

Voigt, S., Buchwitz, M.: On the Mermia ichnofacies in a Triassic overfilled lake-basin of Southern Fergana (Kyrgyzstan, Central Asia). Ichnia 2008, Cracow (Poland), September 1- 5

Abstract. Fluvio-lacustrine deposits of the Madygen Formation on the northern rim of the Turkestan Mountains in southwestern Kyrgyzstan are one of the few occurrences of Triassic continental strata in Central Asia. During the 1960s Russian palaeobiologists successfully explored the stratum typicum area of the Madygen Formation for macrofossils, unearthing a remarkably rich Early Mesozoic flora, thousands of insect remains, and unusual reptiles with soft-tissue preservation (Dobruskina, 1995). Considering the number, diversity and preservation of the finds, the locality represents a lagerstaette. Lacking investigations on the geological and palaeoecological background of the findings, however, its particular importance for the evolution of terrestrial ecosystems has not yet been revealed. Thus, a comprehensive approach on the Madygen ecosystem including a detailed facial analysis of the fossil-bearing strata is currently carried out.
The Madygen Formation is an up to 500 m thick series of predominantly siliciclastic rocks, which formed in an intermontane basin under humid to semi-humid climatic conditions. Sedimentary successions are composed of alluvial fan conglomerates, channel sandstones and overbank fines with intercalated coal seams of a highly-vegetated alluvial plain, as well as deltaic sandstones and laminated lacustrine mudstones of basin centre. Shallowing upward sequences and various other features, e.g. dense vegetation, wet soils, and the lack of desiccation cracks, typify the depositional environment of the Madygen Formation as an overfilled lake-basin sensu Bohacs et al. (2000).
Though they were never mentioned in earlier palaeontological reports, trace fossils of the Mermia ichnofacies belong to the most common phenomena of the Madygen fossil assemblage. Networks of tiny, irregularly branched burrows with high bedding-parallel extension are ubiquitous in the laminated mudstones of the lake deposits. Architecture and size of the burrows indicate deposit-feeding, worm-like trace makers such as the extant oligochaetes and aquatic insect larvae. The bioturbation maximum is recorded in mudstones of the transitional sublittoral to profundal lake zone which probably included a chemocline as in some modern stratified lakes. More shallow but clearly submerged parts of the lake were occupied by benthic ostracods and kazacharthra - triopsid-like branchiopods which are thought to be endemic to the Mesozoic of Central Asia (Chen et al., 1996). Body imprints of the kazacharthra occur spatially close to ribbon- and sickle-shaped trace fossils. We are attributing these traces to different types of kazachartran feeding activity: (1) grazing if the ground water layer is well aerated and (2) short-term mud-diving under oxygen-depleted conditions. All ichnia – the shallow penetrative traces and the presumable kazacharthran traces – were produced in the permanently subaquatic environment of a sizeable lake with a minimum length of 1.7 km. The restriction of trace types to a certain ground level relative to the chemocline may yield a basic approach for the subdivision of the Mermia ichnofacies.

German Paleontological Society Meeting, Erlangen 2008:

Voigt, S., Buchwitz, M., Fischer, J., Krause, D.: Longisquama's dorsal skin appendages: new finds from the type locality. Erlanger Geologische Abhandlungen, Sonderband 6: 117

Abstract. During the 1960s Russian palaeobiologists discovered two incomplete diapsid skeletons with skin impressions in lacustrine shales of the Triassic Madygen Formation, a continental sedimentary succession in southwest Kyrgyzstan, Central Asia. Described by A.G. Sharov in 1970 and 1971 the two finds became known for the uniqueness of the species they represent: While Sharovipteryx mirabilis was an early limb-supported reptilian glider with an exceptionally large uropatagium and probably an archosauromorph, Longisquama insignis, whose systematic position is still controversial, displays a series of elongate hockey-stick-shaped skin projections, rooting along the dorsal midline of the body. The appendages are structurally complex and some morphological features, e.g. the presence of a middle axis and the assumed branching, have motivated their comparison with avian feathers. Apart from four Longisquama paratype specimens with isolated skin appendages no further material belonging to one of the two diapsid species has ever been documented.
Here we report three new finds of the Longisquama appendages which have been recovered from the type locality in the northwestern Madygen outcrop area (Urochishche Dzhaylyau-Cho) during fieldwork in 2007: The single exemplar FG 596/V/1 has a length of 28.9 cm, exceeding all other known specimens by at least 100%. Comparable to the appendages of the holotype it comprises a narrow and relatively long proximal section with a tripartite appearance and a relatively short and wide distal section whose two corrugated longitudinal lobes are separated by a prominent middle axis. The apical end and the basal end are not preserved. FG 596/V/2 and FG 596/V/3 represent 3.6 and 3.7 cm long fragments of the distal section. In FG 596/V/1 and FG 596/V/3 the imprints on the left slab and right slab enclose a thin continuous sedimentary core, a feature which has been regarded as indicative for the overall membranous constitution of the appendages.
Especially the very long specimen FG 596/V/1 has some importance for the developmental and functional interpretation of Longisquama’s skin structures: Exceeding the proximal width of other dorsal appendages by only a small amount its length/ basal width ratio is conspicuously high (>50). This can be interpreted as a consequence of uniaxial growth with the constricted proximal and the extended distal section representing two distinct phases of a developmental cycle. Considering the shape and dimensions of FG 596/V/1 we find no easy explanation how the appendages could have formed a closed and stable airfoil, let alone one which produces enough lift to support gliding flight as assumed by the exponents of the hypothesis of a two-wing airborne Longisquama.

Buchwitz, M., Voigt S.: Dermal plates of a Triassic chroniosuchian with unique articulation mechanism. Erlanger Geologische Abhandlungen, Sonderband 6: 24

Fieldwork Photo of the Week

2008-12-08T14:09:00.000-08:00

Northern Alay Chain, Batken District, SW Kyrgyzstan.

Standing on massive Devonian limestones we are looking to the NNW. On the right you can see the greenish Madygen river oasis bearing a few farms and fruit plantations. On the left: the badlands represent the SW outcrop area of the Triassic Madygen Formation.

To the north and northwest reddish strata and ribs of Cretaceous conglomerate follow which overlie a narrow stripe of Jurassic. Than there is a succession of mostly Cenozoic rocks forming the core of a syncline.

In the distance you can see larger massifs of mostly Paleozoic schists, limestones and conglomerates. And then there is the greenish plain to the northwest marking another outcrop of fineclastic sediments.

This is Dzhaylyau-Cho ("good meadow"), the NW outcrop area of the Madygen Fm, including "Sharov Quarry" as the most famous locality for insects and tetrapods.

Can you see the artificial band-like wall to the west of the Madygen oasis - this is some relic from ancient times (built under Alexander the Great according to a myth).

Fieldwork Photo of the Week

2008-12-01T14:33:00.000-08:00

Two pix from the field camp:

The clubroom buildung, now fully erect and in use. In green: Our cook Ludmilla from Osh.

The penultimate act of packing and repacking one day before the end of the expedition.

Constructivist geoscience and what we can learn from the financial crisis

2008-11-26T15:06:00.000-08:00

The analyses are done. Because you are supposed to do an 'integrated approach' you are working on 'integrating' your data and doing an interpretation that fits in with everything.

After a short or long search for patterns (as a geologist you are at least talented in pattern-spotting), you will find that no easy existing model fits with all data (or worse: every existing model fits with all data) which gives you the chance to chose the model you like best and alter it a bit. You are using an auxilliary hypothesis which explaines why this model, which is adequate in general, is not working properly for the data you are involving.

The best ist to raise a whole set of model assumptions which are not easy to be proven or disproven. Imagine it as a daughter company, to which you can export your credit risks in order to keep the bilance of your adapted existing model clean.

If there are some new data that appear to falsify your model you are employing your daughter company of auxilliary theses to explain why they are not at all problematic.

Given your business concept is good you even manage to invert contradicting data - under the light of your additional theses they actually support your model.

As you can handle it flexibly, you can of course add to or remove from the stock of your daughter company at free will. A good idea is to pay attention to fashions (if 'Milankovich cycles' or 'metamorphic core complexes' or 'climate change' are en vogue you may think about including them).

Successful model constructors manage to give their constructs the appearance of inner coherence (e.g. by means of categories, definitions and a quantitative bluff package) and sell them to others who 'succesfully' convert them to new areas and problems.

And then everything collapses - some new conflicting data pushes your model to the point of absurdity. Usually the new data fit in with a much more parsimonious alternative model. And no one will understand how you could have been so stupid to overlook that possibility in the first place...

Fieldwork Photo of the Weak

2008-11-25T09:08:00.000-08:00

The Neverending Outcrop: Younger stratigraphic succession near Madygen, SW Kyrgyzstan.
The greyish-brownish Madygen Formation is overlayn uncomformably by varicoloured continental Jurassic strata which in turn are separated by an uncomformity from reddish deposits of the facially diverse Cretaceous including massive conglomeratic banks.

Paleogene: A yellowish marine succession containing mass occurrences of oysters and massive carbonates is followed by younger continental deposits of the Tertiary.

Note the roofs of premises belonging to the village of Madygen.

Tectonics & Paleo (III):The shearing of fossils and how to reverse it

2008-11-21T03:03:00.000-08:00

Let's start in 2D: You have a flat fossil and regard only the deformation in the two dimensions of the fossil plane:

Easy, you may say. Fossils specimens like that are good strain indicators and it's not difficult to deduce the amounts of simple shear and flattening/lengthening necessary to transform the undeformed into the deformed specimens or vice versa:

There was a story, my tectonics prof told me from his study time when he was working for a famous German paleontologist: He was doing the retrodeformation of fossils using some kind of algorithm/ computing procedure - but only, until his sponsor found that he could reach the same effect by holding the fossil oblique over a photocopying machine (you can imagine what a disillusionment that was...).

In some cases, however, the problem is not as simple as in the example displayed above. Insect wings from Madygen and other localities often display a considerable amount of deformation but occur isolated and as palaeontological samples they have not been taken oriented (i.e. referenced to a system of external coordinate axes).

What was the original shape?

This question is crucial if you want to define and distinguish taxa (how many unnecessary species have been erected because the similarity of fossil specimens got lost in deformation?) but also searching for intraspecific variation, e.g. branching points that are highly variable in individuals of the same species.

My "bureau-mate" Olivier Bethoux, paleoentomologist, is currently doing his postdoc research working on that problem. I won't say much about his solution which involves morphometrics/ landmark analysis but keep you informed about results when they are published.

Fieldwork Photo of the Week

2008-11-17T16:43:00.000-08:00

You can see the rise of our club room one day after the arrival in Madygen. Gas bottles, sample boxes, and limestone boulders are integral parts of the construction.

Borrowed this photo of a tent erection from this year's Madygen participant Daniel Rutte, who started an exchange semester in Golden, Colorado, shortly after the field trip and after becoming a Bachelor in Freiberg (but only 'of Science' unless I'm much mistaken).

Triassic critters: Kazacharthrans

2008-11-15T13:04:00.000-08:00

Kazacharthrans - or Katzen, as we call them (jokingly) in German - are an endemic group of small branchiopod crustaceans which were named after the former Soviet Republic of Kazakhstan, where the type locality is situated. All yet known occurrences are restricted to the Middle Triassic to Lower Jurassic of Central Asia (Kazakhstan, Mongolia, Turkmenistan, the northwestern Chinese Province Xinjiang, and Kyrgyzstan: the Madygen Formation).

The closest recent relatives of kazacharthrans and an anatomically quite similar group are the tadpole shrimps (Notostraca), including the 'living fossil' species Triops cancriformis, which has not changed since its earliest occurrence in the Triassic.

Kazacharthran head shield from Madygen; width: 1.2 cm.

The most complete body fossils from Madygen consist of a relatively large cephalothoracic shield (see pic) and a segmented tail with a small and spiny shield at the end (telson). Madygen finds show the head shield often considerably deformed. As the animals were subject to moulting, the abundancy of kazachthran body fossils is raised by the preservation of exuviae.

The riddle of kazachrathran radiation. Kazacharthrans are regarded as a Triassic offspring from the lineage of the otherwise conservative group of notostracans which have persisted since the Carboniferous without larger anatomical changes. As the Kazacharthra develop a relatively high diversity (14 genera, >20 species described) in a narrow spatial and temporal window, the crucial questions is, what their speciality (and fate) was.

Sebastian Voigt (who is in charge of the Madygen project here in Freiberg) is a paleoichnologist and also working on kazacharthran trace fossils and their ethological and ecological implications (see ref below), using the ichnia of recent triopsids for comparison (the reminiscence of a childhood dream to have those lovely trackmakers in your aquarium). Understanding the palaeoenvironment and fossil association of kazachathran body and trace fossils in the Madygen Fm will hopefully help to understand the peculiarity of "Katzen".

Refs:

Chen P., K.G. McKennzie & Zhou, H.(1996): A further research into Late Triassic Kazacharthra from Xinjiang Uigur autonomous region, NW China. - Acta Palaeontologica Sinica 35(3): 272-301.

Preliminary results on Madygen kazacharthrans can be found in the abstract volume of the 2007 fall meeting of the German Palaeontological Society (pdf, 33MB):
Voigt, S.(2007): Kazachartran body and trace fossils from shallow lake deposits of the Madygen Formation (Middle to Upper Triassic, Kyrgyzstan, Central Asia). In: O. Elicki & J.W. Schneider (eds): Fossile Ökosysteme. - Wissenschaftliche Mitteilungen 36, Institut für Geologie, TU Freiberg, p. 160

Fieldwork Photo of the Week

2008-11-08T13:32:00.000-08:00

July or August 2007 at "Sharov Quarry": Toilo, who is living in Madygen, is talking to me while I am dripping some fixation solution on a fish or plant fossil.

That pile of weathered shale debris we are sitting on is the product of Sharov's group in the 1960s and of our work. The photo is taken from the position of the outcrop wall.

The Sharov locality is the place where all hiherto described Madygen tetrapods, most insects and fishes, and some of the best plant fossils have been found.

Tectonics & Paleontology (II): Sclerochronology

2008-11-08T11:13:00.000-08:00

Some five years ago I had one of my first presentation-preparing seminars and the list of available topics included 'sclerochronology', supervised by the tectonophysics prof. Searching the literature I found that the term referred to the study of the accretionary growth of mineralized organismic hard parts - a bit like the tree-ring chronology transferred to animal skeletons ('interesting', so I thought and chose 'sclerochronology' for my seminar talk).

There were many papers on mollusc life strategies and environmental change during the younger Cenozoic, mostly analyzing some long-living clams. Not many studies involved 'sclerochronology' as an actual dating method, often researchers were looking for either ontogenetic signals or climatic signals, often involving distinct taxa, localities, and stratigraphic levels for comparison.

Among the animal groups considered were brachiopods, bivalves, corals, belemnites, fish (otoliths) but also higher vertebrates: Enamel and accretionary growing bone can yield sclerochronological data - the method is also called 'skeletochronology' when applied on vertebrate hard parts.

And the link to tectonics? If you consider the cross section of a shell as representing a time series of fast and slow growth phases and phases of arrested growth, how exactly can you expect a tectonic signal to show up? I asked my tectonophysics prof what story he wanted me to tell and it was this:

A reference book on Quaternary dating methods (Lettis et al. 2000) also includes a chapter on sclerochronology in recent to subrecent corals inhabiting a shallow tropical tectonically active shelf. If the shelf area is part of a block which is elevated over another block by thrust faulting (as under compression along a convergent tectonic plate margin), this tectonic movement - which is not continuous but (mostly) discrete with larger earthquakes releasing most of the stress - can have consequences for the coral growth:

During an earthquake (along a thrust fault) the uppermost part of a colony is lifted over the water level, dies, and stops growing, while deeper-lying sections stay intact and continue their growth. If you count the annual growth bands and locate the points of growth arrestment after an earthqake you can derive the timing of earthquakes and also the amount of vertical displacement for each event. These data are sufficient for deriving the earthquake characteristic of the responsible fault - a classical aim of paleoseismology.

You could argue that all that has nothing to do with deep time processes and you are right: While the paleobiological and paleoclimatological approaches employing sclerochronology are not strictly limited in time, sclerochronological dating is restricted to the youngest few thousand years of the Holocene.

Some refs: Sclerochronology

... & Tectonics:
Buddemeier, R.W. & F.W. Taylor (2000): Sclerochronology. In: Lettis, W.R., J.S. Noller & J.M. Sowers (eds): Quarternary Geochronology: Methods and Applications. - Washington, AGU, pages 25- 40.

... in vertebrates
MacFadden, B.J. (2004)(ed): Incremental Growth in Vertebrate Skeletal Tissues: Paleobiological and Paleoenvironmental Implications. In: Palaeogeography, Palaeoclimatology, Palaeoecology 206(3-4).

... in marine animals
Schöne, B.R. & D. Surge (2005)(eds): Looking back over Skeletal Diaries - High-resolution Environmental Reconstructions from Accretionary Hardparts of Aquatic Organisms. In: Palaeogeography, Palaeoclimatology, Palaeoecology 228(1-2).

Tectonics and Paleontology (I): Series Intro

2008-11-02T23:47:00.000-08:00

In Germany paleontologists often have graduated in geoscience study programs. At some universities, such as my Freibergian alma mater, paleontology is mostly taught as a branch of geology dealing with fossils for the purpose of solving geoscientific problems: Fossils provide information about the age of sedimentary rocks (biostratigraphy) or their maturity (see for example: conodont alteration index) or formation conditions (biofacial analysis) or are relevant for paleogeographic reconstructions (paleobiogeography) or for paleoclimatic inference. As a matter of fact fossils are useful and paleontology is not the end in itself, no art pour l'art...

...and so forth. Perhaps some of you heard a similar story.

There are some advantages, though, when you are coming from the geological side: You know your rocks and minerals alright. You have learned how to draw maps and what geoinformation is and all those analytical methods for rock samples and how to get a picture of an ancient biotope from sedimentological criteria and how to find the most fossiliferous places and strata.

In my M.Sc. studies of geology/paleontology I was supposed to chose 3 out of 13 electives, including petrology, tectonics/geodynamics, geology of mineral deposits, geochemistry, sedimentology, pedology, hydrogeology, geotechnics, paleontology, mathematical geology/ geoinformatics and mineralogy. I did a bit of everything with the exception of hydrogeology and focussed on all that non-applied basic research stuff, including paleontology and tectonics.

And when the project in Kyrgyzstan started somewhat later than expected I did - not only for reasons of timing - my master thesis on fissures and normal faults in the Ethiopian rift (see here). Over the years I found more and more links between tectonics and paleontology including rather subtle ones. Some posts will help me to keep them in mind.

Wing types, Sharovipteryx, Longi

2008-10-29T15:38:00.000-07:00

In his review on wing evolution Dietrich Schaller (1985) distinguished wing types according to function, type of wing attachment, and type of airfoil support.

Accordingly there are 'limb wings' and wings not involving limbs. The latter ones can be jointless, such as the pleural wings of Draco and kuehneosaurids, or single-jointed, such as the chitinous wings of insect flapping fliers.

What about the "enigmatic" Madygen beasts?

Sharovipteryx was an early limb-wing glider. Depending on the interpretation of wing topology it is reconstructed either with the fore- and hindlimbs connected by a wing membrane - representing the type of a 'skelobrachial glider' (sensu Schaller) - or with separate brachial (arm) wings and skelosal (leg) wings.

The latter case is discussed in particular by Dyke et al. (2006): Their modelling of the aerodynamic properties of different Sharovipteryx wing configurations demonstrates that a double delta wing morphology would have been the most advantageous for gliding (using certain input conditions based on model assumptions derived from the study of the morphology of the only fossil specimen).

Longisquama as a two-wing glider is not classified as easily. It would possess multi-segment and muli-jointed gliding wings which would constitute airfoils without further structures for support. Schaller did not consider such a configuration. Or else, it would have jointless wings comparable to the membranous muscle-supported flank wings of the gliding gecko Ptychozoon - but with the difference of being segmented, attached to the back and several times as long (minor drawbacks?).

References:

Schaller, D. (1985): Wing Evolution. In: Hecht, M.K., J.H. Ostrom, G. Viohl & P. Wellnhofer: The beginnings of birds. - Eichstätt (Freunde des Juramuseums), pp. 333- 348.

Dyke, G.J., R.L. Nudds & J.M.V. Rayner (2006): Flight of Sharovipteryx mirabilis: the world's first delta-winged glider. - Journal of Evolutionary Biology 19(4): 1040-1043.

World's Largest Mineral Collection

2008-10-26T15:34:00.000-07:00

The opening week of Terra Mineralia is over, setting the signal for the new permament exhibition whithin the walls of the recently restored city castle of Freiberg, Saxony (the most beloved place of my studies besides Madygen).

The exhibition features spectacular pieces from the private collection which Erika Pohl donated to the TU Bergakademie Freiberg. Together with the quite large mineral stock of the Bergakademie's Mineralogical Institute the new gains make the Freibergian collection the largest in the world (...not bad for a town of 40-odd-thousand inhabitants).

The opening celebrations were also the chance for us geoscience students and scientists to communicate what we are doing to the general public and to people from other university departments - so we organized the

GeoDays 2008. Within the premises of Terra Mineralia we had a geo-photo competition, a poster exhibition, and a small program of lectures and presentations on 3D modelling, sand, soil, moon rocks, saxonian vertebrate fossils etc.

Among other GeoDays volunteers I was also involved in the children's program: For some hours between Thursday and Saturday I was responsible for the "raw material" station in a point-collecting game:

The children had to connect objects of daily use with the minerals which served as raw materials - an idea realized by Alexandra Käßner, another PhD student of the geological institute (nice one, Alex!)

.... though it is not easy to keep countenance when you have two kindergarten groups - ten kids each - standing around you, keen on solving the quest in order to get a point. (The price? - I think some small colourful polished piece of mineral).

Go here for some GeoTage impressions (including me in the first pic).

Rock-paper-scissors

2008-10-18T09:26:00.000-07:00

Unpacking of the 2008 finds in a rather relaxed "subbotnik".
This year's fieldwork season turned out to be a good one for plants and for Philippe Moisan Tapia, palaeobotanist and graduate student at the University of Münster - he is doing his dissertation on the Madygen flora.

Triassic critters: Titanopterans

2008-10-15T15:53:00.000-07:00

Among the most remarkable fossil insects from Madygen are the titanopterans which can reach wing spans of 50 cm. The Titanoptera form a subgroup of the Neoptera and were usually regarded as having an order rank when the Linnean taxonomic system is applied.

Recently, there was a revision done by Olivier Béthoux, who is currently working as a Humboldt research fellow at the geological institute of my alma mater (actually he is my "bureau mate"):

Béthoux (2007): Cladotypic taxonomy applied: Titanopterans are Orthopterans. - Arthropod Systematics & Phylogeny 65(2): 135- 156.

Recent orthopterans include grasshoppers and crickets. Olivier Béthoux shows on the basis of wing venation topology that members of a Permian "family" of Orthoptera - the Tcholmanvissiidae - are the closest relatives of the Triassic group Titanoptera. Such a relationship was also proposed by Madygen researcher A. G. Sharov as early as 1968 but later doubted by others.

The 'Titanopterida' are newly defined as a subgroup of the 'Tcholmantitanopterida' which are in turn a subgroup of Tcholmanvissiidae:

"Species that evolved from the (segments of) metapopulation lineage in which the character state ‘in forewing, CuPaα• + CuPaβ and CuPb having the same point of origin’, as exhibited by giganteus Tillyard, 1916 and vulgaris Sharov, 1968, has been acquired." (see page 145)

The cryptic formulas refer to higher order branches of the posterior Cubitus (CuP), a main wing veine.

Olivier's paper is interesting for another reason: As announced in the title he uses the relationship of titanopterans as an example for applying his concept of cladotypic taxonomy which on its own may be worth a post here (after I got the point). One part of his idea may be frightening for some biologists - as in the definition above there is no longer a need for binary nomenclature.

Fieldwork Photo of the Week

2008-10-15T09:09:00.000-07:00

Blue-collar workers: undergrads Daniel & Juliane plus me.

Longisquama paper in press

2008-10-13T18:38:00.000-07:00

Link to online first version:

Voigt, S. Buchwitz, M., Fischer, J., Krause, D. & Georgi, R.(2008): Feather-like development of Triassic diapsid skin appendages. - Naturwissenschaften

The paper introduces some new finds (appendage fragments found in 2007) and a specific interpretation which aspects of development can be inferred from the morphology of the complex appendage fossil.

Madygen: never heard? - for sure you did

2008-10-13T16:35:00.000-07:00

hear about Longisquama and Sharovipteryx, the notorious "engimatic small diapsids" that are discussed every other year for their phylogenetic relevance and/or functional morphology.

Both come from a thin slice of lake sediments within the Triassic Madygen Formation, a several hundred meter thick succession of continental sedimentary rocks.

For the first time distinguished by KOCHNEV (1934) in an unpublished report and named after the village Madygen, the fossiliferous sediments came into the focus of Soviet palaeobiologists from Moscow, who carried out several excavations during the 1960s.

Madygen became a classic locality and primary source for Early Mesozoic insects. Moreover the group discovered macrofloral remains, molluscs, crustaceans, fish, an urodelan, a cynodont and two small skeletons of diapsid reptiles. The latter were described by the great Russian palaeoentomologist ALEXANDER G. SHAROV between 1966 and 1971.

Several approaches focussed on the sedimentology and stratigraphy of the Madygen Fm - a geological mapping and analysis of the flora by DOBRUSKINA (e.g. 1995) delivered a Ladinian- Carnian age.

During the last three years, palaeontological fieldwork in Madygen intensified again when the far-off realm of SW Kygrgyzstan was again headed for by a Moscovian group of palaeontologists and by a German research group.

----
Some refs (see also linked WP articles of Longisquama & Sharovipteryx):

Sharov, A.G. (1966): [Unique discoveries of reptiles from Mesozoic beds of Central Asia.] - Bjulleten Moskovskogo Obscestva Ispytatelej Prirody, Otdel geologiceskij, 61 (2): 145- 146 (Moscow).

Dobruskina, I.A. (1995): Keuper (Triassic) Triassic Flora from Middle Asia (Madygen, Southern Fergana). - New Mexico Museum of Natural History and Science Bulletin 5: 1-49

Preamble

2008-10-13T12:22:00.000-07:00

REMEMBERING the golden age of rising rationality when Haeckel convinced the unknowing masses with a multimedia show of colourful posters and bottles of (manipulated) embryos

WITH THE AIM of promoting the study of a worthwhile fossil site and its countless treasures

CRAVING for salvation in the heavenly realm of barrier-free communication

WITH THE CONFIDENCE that sharing our nerdy views can be therapeutical for us and alien beings alike

UNAWARE of the blogospherical disturbances and paracademic noise lying before us and

SALUTING to the free spirits of earth and life science

we, Michael of Freiberg, have started this palaeo/geo blog. "Hello world!"