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.
Posts mit dem Label archosaurs werden angezeigt. Alle Posts anzeigen
Posts mit dem Label archosaurs werden angezeigt. Alle Posts anzeigen
Dienstag, 27. März 2012
Mittwoch, 30. März 2011
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.
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.
Donnerstag, 2. Dezember 2010
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]
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]
Samstag, 17. Oktober 2009
Madygen News 2009
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.
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.
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.
Samstag, 25. Juli 2009
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.
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.
Donnerstag, 14. Mai 2009
PALHERP Bonn 2009
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.
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.
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