The Longisquama paper in press got some media coverage

Science writer Jeff Hecht wrote an article discussing results of our study:

Jeff Hecht: Reptile grew feather-like structures before dinosaurs. New Scientist, issue 2857, 23 March 2012.

Was a bit afraid of this, because often a finely nuanced statement is cited incorrectly or even turned into the opposite when the message of a paper is adapted for a non-specialist audience. Looks okay, though.

New papers on Kyrgyzsaurus, Madygenerpeton, and Longisquama

Alifanov, V. R. and E. N. Kurochkin. 2011..Kyrgyzsaurus bukhanchenkoi gen. et sp. nov., a new reptile from the Triassic of southwestern Kyrgyzstan. Paleontological Journal 45(6):639-647.
[DOI: 10.1134/S0031030111060025] [link]

Description of a reptile fossil with skin preservation discovered in 2006. Comes form the same locality as Sharovipteryx and Longisquama. The authors interpret the specimen as a member of drepanosaurs, a Late Triassic group of archosauromorphs. This paper represents one of the last contributions of the Russian palaeornithologist Evgenii N. Kurochkin who passed away recently.

Buchwitz, M., C. Foth, I. Kogan, and S. Voigt. 2012 in press. On the use of osteoderm features in a phylogenetic approach on the internal relationships of the Chroniosuchia (Tetrapoda: Reptiliomorpha). Palaeontology. [DOI: 10.1111/j.1475-4983.2012.01137.x] [link]

Includes a graphic reconstruction of Madygenerpeton (drawing by Frederik Spindler).

Buchwitz, M. and S. Voigt. 2012 in press. The dorsal appendages of the Triassic reptile Longisquama insignis: reconsideration of a controversial integument type. Paläontologische Zeitschrift.
[DOI: 10.1007/s12542-012-0135-3] [Link]

More thorough description/ graphic documentation compared to Voigt et al.(2009) and considers some aspects of diapsid skin evolution.

Chroniosuchia: Paper on osteoderm histology in online preview

...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.

Three recent papers on chroniosuchians

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

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

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]

Reptile from the Petrified Forest of Chemnitz

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").

EAVP Meeting 2009 in Berlin, Germany

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

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

Or what the hell is this?

Lineage concept vs cladistics in continental biostratigraphy

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.