Sobral, G., Sues, H.-D., and J. Müller. 2015. Anatomy of the enigmatic reptile Elachistosuchus
huenei Janensch, 1949 (Reptilia: Diapsida) from the
Upper Triassic of Germany and its relevance for the
origin of Sauria. PLoS ONE 10(9): e0135114.
doi:10.1371/journal.pone.0135114
Abstract - The holotype and only known specimen of the enigmatic small reptile Elachistosuchus huenei
Janensch, 1949 from the Upper Triassic (Norian) Arnstadt Formation of Saxony-Anhalt
(Germany) is redescribed using μCT scans of the material. This re-examination revealed
new information on the morphology of this taxon, including previously unknown parts of the
skeleton such as the palate, braincase, and shoulder girdle. Elachistosuchus is diagnosed
especially by the presence of the posterolateral process of the frontal, the extension of the
maxillary tooth row to the posterior margin of the orbit, the free posterior process of the
jugal, and the notched anterior margin of the interclavicle. Phylogenetic analyses using two
recently published character-taxon matrices recovered conflicting results for the phylogenetic
position of Elachistosuchus–either as an archosauromorph, as a lepidosauromorph or
as a more basal, non-saurian diapsid. These different placements highlight the need of a
thorough revision of critical taxa and new character sets used for inferring neodiapsid
relationships.
Showing posts with label Diapsids. Show all posts
Showing posts with label Diapsids. Show all posts
Redescription of the Middle Triassic Diapsid Megachirella wachtleri, an Early Branching Lepidosauromorph
Renesto, S., and M. Bernardi. 2013. Redescription and phylogenetic relationships of Megachirella wachtleri Renesto et Posenato, 2003 (Reptilia, Diapsida). Paläontologische Zeitschrift. DOI: 10.1007/s12542-013-0194-0
Abstract - Megachirella wachtleri Renesto et Posenato, 2003, a well preserved partial reptile skeleton from the Middle Triassic of the Dolomites (N. Italy), was originally considered a lepidosauromorph, but no phylogenetic analysis was carried out. Consequently, the taxon was overlooked in later phylogenetic analyses of the Diapsida. Here, the holotype and only known specimen of M. wachtleri is redescribed, allowing an investigation of its phylogenetic relationships. Phylogenetic analyses confirm that Megachirella is a lepidosauromorph close to the crown group lepidosaurs (Squamata + Rhynchocephalia). Megachirella enhances our knowledge of the series of morphological modifications that led to the origin of the Lepidosauria, the most diverse clade of extant reptiles.
Abstract - Megachirella wachtleri Renesto et Posenato, 2003, a well preserved partial reptile skeleton from the Middle Triassic of the Dolomites (N. Italy), was originally considered a lepidosauromorph, but no phylogenetic analysis was carried out. Consequently, the taxon was overlooked in later phylogenetic analyses of the Diapsida. Here, the holotype and only known specimen of M. wachtleri is redescribed, allowing an investigation of its phylogenetic relationships. Phylogenetic analyses confirm that Megachirella is a lepidosauromorph close to the crown group lepidosaurs (Squamata + Rhynchocephalia). Megachirella enhances our knowledge of the series of morphological modifications that led to the origin of the Lepidosauria, the most diverse clade of extant reptiles.
The First Detailed 3D visualizations of the Braincase and Vestibular System in a Permian Diapsid Reptile
Not Triassic but sill extremely significant for work on Triassic archosauromorphs as Youngina is often used as an outgroup for phylogenetic studies of this clade. Great new information, extremely cool, and of course open access!
Gardner, N. M., Holliday, C. M., anf F. R. O'Keefe. 2010. The braincase of Youngina capensis (Reptilia: Diapsida): new insights from high-resolution CT scanning of the holotype. Palaeontologia Electronica 13.3.19A.
Abstract - Detailed descriptions of braincase anatomy in early diapsid reptiles have been historically rare given the difficulty of accessing this deep portion of the skull, because of poor preservation of the fossils or the inability to remove the surrounding skull roof. Previous descriptions of the braincase of Youngina capensis, a derived stem-diapsid reptile from the Late Permian (250 MYA) of South Africa, have relied on only partially preserved fossils. High resolution X-ray computed tomography (HRXCT) scanning, a new advance in biomedical sciences, has allowed us to examine the reasonably complete braincase of the holotype specimen of Youngina capensis for the first time by digitally peering through the sandstone matrix that filled the skull postmortem. We present the first detailed 3D visualizations of the braincase and the vestibular system in a Permian diapsid reptile. This new anatomical description is of great comparative and phylogenetic relevance to the study of the structure, function and evolution of the reptilian head.
Gardner, N. M., Holliday, C. M., anf F. R. O'Keefe. 2010. The braincase of Youngina capensis (Reptilia: Diapsida): new insights from high-resolution CT scanning of the holotype. Palaeontologia Electronica 13.3.19A.
Abstract - Detailed descriptions of braincase anatomy in early diapsid reptiles have been historically rare given the difficulty of accessing this deep portion of the skull, because of poor preservation of the fossils or the inability to remove the surrounding skull roof. Previous descriptions of the braincase of Youngina capensis, a derived stem-diapsid reptile from the Late Permian (250 MYA) of South Africa, have relied on only partially preserved fossils. High resolution X-ray computed tomography (HRXCT) scanning, a new advance in biomedical sciences, has allowed us to examine the reasonably complete braincase of the holotype specimen of Youngina capensis for the first time by digitally peering through the sandstone matrix that filled the skull postmortem. We present the first detailed 3D visualizations of the braincase and the vestibular system in a Permian diapsid reptile. This new anatomical description is of great comparative and phylogenetic relevance to the study of the structure, function and evolution of the reptilian head.
New Study Suggests that Turtles are not Diapsids
Lyson, T. R., G. S. Bever, B. S. Bhullar, W. G. Joyce and J. A. Gauthier. In press. Transitional fossils and the origin of turtles. Biology Letters published online before print June 9, 2010, doi:10.1098/rsbl.2010.0371
Abstract - The origin of turtles is one of the most contentious issues in systematics with three currently viable hypotheses: turtles as the extant sister to (i) the crocodile-bird clade, (ii) the lizard-tuatara clade, or (iii) Diapsida (a clade composed of (i) and (ii)). We reanalysed a recent dataset that allied turtles with the lizard-tuatara clade and found that the inclusion of the stem turtle Proganochelys quenstedti and the 'parareptile' Eunotosaurus africanus results in a single overriding morphological signal, with turtles outside Diapsida. This result reflects the importance of transitional fossils when long branches separate crown clades, and highlights unexplored issues such as the role of topological congruence when using fossils to calibrate molecular clocks.
Abstract - The origin of turtles is one of the most contentious issues in systematics with three currently viable hypotheses: turtles as the extant sister to (i) the crocodile-bird clade, (ii) the lizard-tuatara clade, or (iii) Diapsida (a clade composed of (i) and (ii)). We reanalysed a recent dataset that allied turtles with the lizard-tuatara clade and found that the inclusion of the stem turtle Proganochelys quenstedti and the 'parareptile' Eunotosaurus africanus results in a single overriding morphological signal, with turtles outside Diapsida. This result reflects the importance of transitional fossils when long branches separate crown clades, and highlights unexplored issues such as the role of topological congruence when using fossils to calibrate molecular clocks.
Feather-like development of Triassic diapsid skin appendages
Thanks to Rob Taylor of the Theropod Archives who just posted on the Dinosaur Mailing List that Naturwissenschaften is freely available online through the end of the month. One of several Online First Titles that is of interest is this one...
Voight, S., Buchwitz, M., Fischer, J., Krause, D., and R. Georgi. Online First 2008. Feather-like development of Triassic diapsid skin appendages. Naturwissenschaften
DOI 10.1007/s00114-008-0453-1
Abstract - Of the recent sauropsid skin appendage types, only feathers develop from a cylindrical epidermal invagination, the follicle, and show hierarchical branching. Fossilized integuments of Mesozoic diapsids have been interpreted as follicular and potential feather homologues, an idea particularly controversially discussed for the elongate dorsal skin projections of the small diapsid Longisquama insignis from the Triassic of Kyrgyzstan. Based on new finds and their comparison with the type material, we show that Longisquama’s appendages consist of a single-branched internal frame enclosed by a flexible outer membrane. Not supporting a categorization either as feathers or as scales, our analysis demonstrates that the Longisquama appendages formed in a two-stage, feather-like developmental process, representing an unusual early example for the evolutionary plasticity of sauropsid integument.
The PDF and online supplemental material is also available from the same site.
Voight, S., Buchwitz, M., Fischer, J., Krause, D., and R. Georgi. Online First 2008. Feather-like development of Triassic diapsid skin appendages. Naturwissenschaften
DOI 10.1007/s00114-008-0453-1
Abstract - Of the recent sauropsid skin appendage types, only feathers develop from a cylindrical epidermal invagination, the follicle, and show hierarchical branching. Fossilized integuments of Mesozoic diapsids have been interpreted as follicular and potential feather homologues, an idea particularly controversially discussed for the elongate dorsal skin projections of the small diapsid Longisquama insignis from the Triassic of Kyrgyzstan. Based on new finds and their comparison with the type material, we show that Longisquama’s appendages consist of a single-branched internal frame enclosed by a flexible outer membrane. Not supporting a categorization either as feathers or as scales, our analysis demonstrates that the Longisquama appendages formed in a two-stage, feather-like developmental process, representing an unusual early example for the evolutionary plasticity of sauropsid integument.
The PDF and online supplemental material is also available from the same site.
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