Stocker, M. R.. 2013. A new taxonomic arrangement for Paleorhinus scurriensis. Earth and Environmental Science Transactions of the Royal Society of Edinburgh (advance online publication)DOI: http://dx.doi.org/10.1017/S1755691013000340
Abstract - The paraphyletic genus ‘Paleorhinus’ is understood currently as a cosmopolitan phytosaur taxon from the Late Triassic. There is no consensus regarding the number of species of ‘Paleorhinus,’ with multiple species and genera synonymised into a single genus or even a single species at various points in its published history. The taxonomy is confounded by historical descriptions without the benefit of comparisons to more recently collected specimens, emphasis on plesiomorphic cranial morphology as diagnostic features of the genus,
and lack of cladistic analyses. When included in a recent explicitly cladistic phylogenetic analysis, the holotype of ‘Paleorhinus’ scurriensis (TTU P-00539) was found to be the earliest-branching phytosaur with respect to other North American specimens previously referred to ‘Paleorhinus,’ and is generically distinct from Paleorhinus. ‘Paleorhinus’ scurriensis differs from all known phytosaurs in five unambiguous characters: basitubera widely separated mediolaterally; ridge present on lateral surface of jugal; thickened shelf present along posteroventral edge of expanded pterygoid-quadrate wing; ‘septomaxillae’ separated and excluded from internarial septum; and nasal swelling present posterior to posterior borders of nares. This detailed morphological description of an early-branching phytosaur taxon is a first step towards resolving long-standing issues surrounding specific anatomical features and relationships among early members of the clade.
Hungerbühler, A., Mueller, B., Chatterjee, S., and D. P. Cunningham. 2013. Cranial anatomy of the Late Triassic phytosaur Machaeroprosopus, with the description of a new species from West Texas. Earth and Environmental Science Transactions of the Royal Society of Edinburgh (advance online publication) DOI: http://dx.doi.org/10.1017/S1755691013000364
Abstract - The skull anatomy of a new species of the phytosaur Machaeroprosopus is described for the first time on the basis of two specimens from the Upper Triassic Cooper Canyon Formation of Texas. Additional information is provided by a third specimen referred to Machaeroprosopus sp. A paranasal bone, an additional paired element of the narial region, is identified. Important new data are presented for the braincase, including the morphology of the epipterygoid and presphenoid, an anterior process of the prootic, an anteroventral process of the laterosphenoid, and a parasphenoid process. Machaeroprosopus lottorum n. sp. is characterised by four apomorphies: a supratemporal fenestra closed on the skull roof with beveled anterior rim, a comparatively short squamosal, a flat and rugose narial rim, and medially extended palatines that come close to form an ossified secondary palate. With respect to the supratemporal fenestra, the supraoccipital–parietal complex and several features of the squamosal, Machaeroprosopus lottorum n. sp. bridges the morphological gap between species previously referred to the genera Pseudopalatus and Redondasaurus. A parsimony analysis of known species of Machaeroprosopus supports the hypothesis that the development of the rostral crest in Machaeroprosopus is a sexually dimorphic feature, and questions the validity of the genus Redondasaurus. Consequently, Redondasaurus is here considered a junior synonym of Machaeroprosopus.
Showing posts with label Texas. Show all posts
Showing posts with label Texas. Show all posts
New Triassic Papers in the Festschift in Honor of Dr. Wann Langston Jr.
Back in very early 2010 Dr. Ernie Lundelius was honored with a festschift volume. When I congratulated him on it he lamented that his close friend and colleague Dr. Wann Langston Jr., still did not have a festschift in his honor. Ernie said they had tried to get one going a few times but nothing had ever come of it. I agreed to help to start another one and after several trials am proud to announce that the first online papers are now available from the Earth and Environmental Transactions of the Royal Society of Edinburgh. The final print volume will be out a bit later. Unfortunately Dr. Langston passed away earlier this year and did not get to see the completed volume; however he did get to see a compilation of the abstracts.
Dr. Langston was Charles L. Camp's graduate student at the University of California at Berkeley and althogh his dissertation was on Permian vertebrates of North America, one of his firs publications was a description of a new phytosaur from the Upper Triassic of Texas. Thus it is fitting that there are a few Triassic papers in his festschrift volume. Two, which I was involved with, are up currently: I'll post the rest when they come online.
Parker, W. G. 2013. Redescription and taxonomic status of specimens of Episcoposaurus and Typothorax, the earliest known aetosaurs (Archosauria: Suchia) from the Upper Triassic of western North America, and the problem of proxy “holotypes”. Earth and Environmental Transactions of the Royal Society of Edinburgh First View Article. DOI: http://dx.doi.org/10.1017/S1755691013000212
Martz, J. W., Mueller, B., Nesbitt, S. J., Stocker, M. R., Parker, W. G., Atanassov, M., Fraser, N., Weinbaum, J., and J. R. Lehane. 2013. A taxonomic and biostratigraphic re-evaluation of the Post Quarry vertebrate assemblage from the Cooper Canyon Formation (Dockum Group, Upper Triassic) of southern Garza County, western Texas. Earth and Environmental Transactions of the Royal Society of Edinburgh First View Article. DOI: http://dx.doi.org/10.1017/S1755691013000376
Dr. Langston was Charles L. Camp's graduate student at the University of California at Berkeley and althogh his dissertation was on Permian vertebrates of North America, one of his firs publications was a description of a new phytosaur from the Upper Triassic of Texas. Thus it is fitting that there are a few Triassic papers in his festschrift volume. Two, which I was involved with, are up currently: I'll post the rest when they come online.
Parker, W. G. 2013. Redescription and taxonomic status of specimens of Episcoposaurus and Typothorax, the earliest known aetosaurs (Archosauria: Suchia) from the Upper Triassic of western North America, and the problem of proxy “holotypes”. Earth and Environmental Transactions of the Royal Society of Edinburgh First View Article. DOI: http://dx.doi.org/10.1017/S1755691013000212
Abstract - Historic type and referred material of the aetosaurian taxa Typothorax coccinarum, Episcoposaurus horridus and Episcoposaurus haplocerus are redescribed and the non-aetosaurian material identified and removed, a task previously considered “hopeless”. Reexamination of the original material reveals that the holotypes of E. haplocerus and probably T. coccinarum are not diagnosable at the species level and therefore are nomena dubia. The next available names for material referred to these taxa are Desmatosuchus spurensis and E. horridus respectively, although it may be more desirable for reasons of taxonomic stability to attempt to petition for a neotype in the latter case. The redescription of historical specimens is necessary to determine their nomenclatural validity. The use of referred specimens as proxy “type” specimens is problematic, as these referrals were originally made not on the basis of apomorphies, but rather on biostratigraphic and/or geographical assumptions which are inherently circular and cannot be unambiguously supported.
Abstract - The Post Quarry, within the lower part of the type section of the Upper Triassic Cooper Canyon Formation in southern Garza County, western Texas, contains a remarkably diverse vertebrate assemblage. The Post Quarry has produced: the small temnospondyl Rileymillerus cosgriffi; the metoposaurid Apachesaurus gregorii; possible dicynodonts and eucynodonts; a clevosaurid sphenodontian; non-archosauriform archosauromorphs (Trilophosaurus dornorum, simiosaurians, and possibly Malerisaurus); the phytosaur Leptosuchus; several aetosaurs (Calyptosuchus wellesi, Typothorax coccinarum, Paratypothorax, and Desmatosuchus smalli); the poposauroid Shuvosaurus inexpectatus (“Chatterjeea elegans”); the rauisuchid Postosuchus kirkpatricki; an early crocodylomorph; several dinosauromorphs (the lagerpetid Dromomeron gregorii, the silesaurid Technosaurus smalli, a herrerasaurid, and an early neotheropod); and several enigmatic small diapsids. Revised lithostratigraphic correlations of the lower Cooper Canyon Formation with the Tecovas Formation, the occurrence of Leptosuchus, and the overall composition of the assemblage indicate that the Post Quarry falls within the Adamanian biozone, and not the Revueltian biozone. Stratigraphic subdivision of the Adamanian biozone may be possible, and the Post Quarry may be correlative with the upper part of the Adamanian biozone in Arizona. The age of the Post Quarry assemblage is possibly late Lacian or earliest Alaunian (late early Norian or earliest middle Norian), between 220 and 215 Ma.
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