Bone Histology of Phytosaur, Aetosaur, and Other Archosauriform Osteoderms

Just in time for Christmas...

Scheyer, T. M., Desojo, J. B., and I. A. Cerda. 2013. Bone histology of phytosaur, aetosaur, and other archosauriform osteoderms (Eureptilia, Archosauromorpha). Anatomical Record (early view) DOI: 10.1002/ar.22849

Abstract - As in other archosauriforms, phytosaurs and aetosaurs are characterized by the presence of well-developed osteoderms. Here we provide a comparative study on the microstructure of phytosaur (five taxa) and aetosaur (thirteen taxa) osteoderms. For outgroup comparison, we sampled osteoderms of the sister taxon to Aetosauria, Revueltosaurus callenderi, and the doswelliid Jaxtasuchus salomoni. Phytosaur, aetosaur, and Jaxtasuchus osteoderms are composed of a diploe structure, whereas the Revueltosaurus osteoderm microanatomy is more compact. The external cortex of phytosaurs, Revueltosaurus and Jaxtasuchus osteoderms is mainly composed of parallel-fibered bone. In aetosaurs, the external cortex mainly consists of lamellar bone, with lines of resorption within the primary bone indicating successive cycles of bone erosion and deposition. The basal cortex in all the specimens is composed of parallel-fibered bone, with the cancellous internal core being more strongly developed in aetosaurs than in phytosaurs. Woven or fibro-lamellar bone was recorded in both phytosaurian and aetosaurian taxa, as well as in Jaxtasuchus. Structural fibers, which at least partly suggest metaplastic origin, were only recorded in the internal core of two phytosaurs and in the
basal cortex of one aetosaur. Osteoderm thickness and cancellous to compact bone ratios appear to be subject to ontogenetic change. Minimum growth mark counts in osteoderms sampled indicate that some aetosaurs and phytosaurs lived for at least two decades. Bone microstructures are more uniform in phytosaur osteoderms and show a higher level of disparity among aetosaur osteoderms, and at least in the latter, histological features are potentially apomorphic for species/genus level.

Standardizing Triassic Stratigraphic Nomenclature in New Mexico

This is a new paper written by a group of geologists who are largely responsible for conducting much of the current geological mapping in New Mexico, and is an attempt to standardize the nomenclature used for Phanerozoic rocks especially the Triassic. Key recommendations regarding the Triassic rocks are abandonment of the Chinle as a Group and keeping it at the formation level, removal of the Dockum from the "Chinle Group" and reinstatement as the Dockum Group as traditionally used, and a suggestion where to divide strata between the Chinle and Dockum.  Consideration of the Chinle as a group and subsuming the Dockum has been controversial and never fully accepted since it was first proposed in the early 1990s. Thus, this paper suggests abandonment of much of the nomenclature proposed by Spencer Lucas and colleagues over the last couple of decades.

Cather, S. M., Zeigler, K. E., Mack, G. H., and S. A. Kelley. 2013. Toward standardization of Phanerozoic stratigraphic nomenclature in New Mexico. Rocky Mountain Geology 48:101-124. doi:10.2113/gsrocky.48.2.101
 
Abstract - Nomenclature for Phanerozoic strata in New Mexico has been rapidly evolving, but not all proposed changes have been widely accepted. From a perspective of geologic mapping, we evaluate some recent nomenclatural proposals for Pennsylvanian, Permian, Triassic, Jurassic, and Paleogene units. Because of the long shelf-life of geologic quadrangle maps and the desirability of minimizing nomenclatural diversity among them, we present guidelines with which we argue for a conservative approach to changes in stratigraphic nomenclature.

Redescription of "Paleorhinus" (Phytosauria) Specimens from Germany

Butler, R. J., Rauhut, O. W. M., Stocker, M. R., and R. Bronowicz. 2013. Redescription of the phytosaurs Paleorhinus (‘Francosuchus’) angustifrons and Ebrachosuchus neukami from Germany, with implications for Late Triassic biochronology. Zoological Journal of the Linnean Society Early View. DOI: 10.1111/zoj.12094

 
Abstract - Phytosaurs are a diverse and morphologically distinctive clade of superficially crocodile-like archosauriforms that had a near global distribution during the Late Triassic. Because their remains are among the most abundant vertebrate remains recovered in many Upper Triassic terrestrial formations, phytosaurs are used extensively in long-range biochronological and biostratigraphic correlations. The biochronologically oldest and earliest branching known phytosaurs include an array of nominal species from the early Late Triassic of the United States, Germany, Poland, Morocco, and India that have been synonymized within the genus Paleorhinus, and subsequently used to define a global ‘Paleorhinus biochron’. However, recent phylogenetic work suggested that the North American species previously referred to Paleorhinus are paraphyletic. Here, we reassess the systematics and anatomy of putative specimens of Paleorhinus from southern Germany. Two well-preserved basal phytosaur skulls from the Blasensandstein (Carnian) of Bavaria form the holotypes of Francosuchus angustifrons and Ebrachosuchus neukami, both of which were synonymized with Paleorhinus by previous workers. We demonstrate that Francosuchus angustifrons shares unique synapomorphies with specimens referred to Paleorhinus bransoni from the Late Triassic of Texas, and thus refer the species to Paleorhinus. By contrast, the longirostrine Ebrachosuchus is highly distinctive in morphology, and our new cladistic analysis of Phytosauria demonstrates that it represents a valid taxon that is more closely related to Phytosauridae than to Paleorhinus. We provide the first autapomorphy-based support for a monophyletic but restricted Paleorhinus (supported by a nodal row on the jugal, and low paired ridges on the squamosal) and confirm that previous broader conceptions of Paleorhinus are likely to be paraphyletic.

Mammal-like Tooth from the Upper Triassic of Poland

 Świło, M., Niedźwiedzki, G., and T. Sulej. 2013. Mammal-like tooth from the Upper Triassic of Poland. Acta Palaeontologica Polonica Accepted Manuscript doi:http://dx.doi.org/10.4202/app.00016.2013.

Abstract - Triassic discoveries have extended the record of near-mammals (Mammaliaformes) back to the Norian, about 215 Ma, and reveal a significant diversity of Late Triassic (Norian-Rhaetian) forms. We now add to this Late Triassic diversity a nearly complete double-rooted right lower molariform tooth (ZPAL V.33/734) from the Polish Upper Triassic that is significant because it comes from uppermost Norian–lower Rhaetian rocks and is the first discovery of a mammal-like tooth in the Mesozoic of Poland. The described tooth shows transitional dental morphology between advanced cynodonts and mammaliaforms and it appears to represent a basal mammaliaform (Hallautherium genus), probably belonging to Morganucodonta.

Colorado Plateau Coring Project

Coring is currently underway in Petrified Forest National Park targeting the Chinle and Moenkopi Formations.

You can read about the project and follow the links to the main project page and daily blog from here. The main page is here.

There is also a Facebook page with numerous updates.

Please check this project out. The beautiful logo was designed by Steven Seppi.

A New Specimen of the Middle Triassic Archosauriform Shansisuchus shansisuchus from China

Wang, R., Xu, S., , Wu, X., Li, C., and S. Wang. 2013. A New Specimen of Shansisuchus shansisuchus Young, 1964 (Diapsida: Archosauriformes) from the Triassic of Shanxi, China. Acta Geologica Sinica (English Edition) 87:1185-1197 DOI: 10.1111/1755-6724.12145

Abstract - Shansisuchus shansisuchus Young, 1964 was restudied on the basis of a new specimen. Some anatomical features that were either briefly or not described at all in the original study were detailed. The new specimen not only provides further information on the skull anatomy and the vertebral column but also expands the range of the geographical distribution of the taxon. With new information, the diagnosis of S. shansisuchus was emended and its phylogenetic relationships were further analyzed. S. shansisuchus differs from other archosauriforms primarily in the presence of a large subnarial fenestra anterior to the antorbital fenestra, tongue- n-groove articulations between the ascending process of the premaxilla and nasal and between the premaxilla and maxilla, a tall and posterodorsally directed ascending process of the maxilla, a knee-shaped process of the postorbital projecting into the orbit, a broad descending process of squamosal distally well forked and a large, deeply bow-shaped intercentrum tightly anchoring/capping the sharp ventral edges of two neighboring centra together in cervical and at least first eight dorsal vertebrae. With additional information derived from the new specimen, the phylogenetic relationships of S. shansisuchus were reanalyzed; it is closely related to Erythrosuchus-Vjushkovia clade.

Two New Late Triassic Phytosaur Papers

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.

Ignotosaurus fragilis, a New Silesaurid Dinosauriform from the Late Triassic of Argentina and the Vertebrate Succession of the Ischigualasto Formation

Martínez, R. N., Apaldetti, C., Alcober, O. A., Colombi, C. E., Sereno, P. C., Fernandez, E., Santi Malnis, P., Correa, G. A., and D. Abelin. 2013. Vertebrate succession in the Ischigualasto
Formation, Journal of Vertebrate Paleontology, 32:sup1, 10-30, DOI: 10.1080/02724634.2013.818546

Abstract - The Upper Triassic (Carnian–Norian) Ischigualasto Formation has yielded a diverse vertebrate fauna that records the initial phase of dinosaur evolution. Radioisotopic dates from ash layers within the formation provide a chronostratigraphic framework, and stratigraphic and sedimetological studies have subdivided the formation into four members and three abundance-based biozones. We describe two new basal dinosauromorphs, an unnamed lagerpetid and a new silesaurid, Ignotosaurus fragilis, gen. et sp. nov., which increase to 29 the number of vertebrates in the Ischigualasto fauna. We provide a census of 848 fossil specimens representing 26 vertebrate taxa logged to stratigraphic intervals of 50 m. This temporally calibrated census shows that abundance and taxonomic diversity within the Ischigualasto Formation does not change suddenly but rather appears to gradually decline in response to climatic deterioration. The only abrupt shift in faunal composition occurs at the end of the second of three biozones, when the abundant cynodont Exaeretodon is replaced by the rare dicynodont Jachaleria.

Osteology of Eoraptor lunensis

Finally this is published. Now if I can just get the Revueltosaurus monograph out all will be right in the Triassic world, right?

Sereno, P. C., Martínez, R. N.,  and  O. A. Alcober. 2013. Osteology of Eoraptor lunensis (Dinosauria, Sauropodomorpha). Journal of Vertebrate Paleontology Memoir 12:83-179.

Abstract - We describe the basal sauropodomorph Eoraptor lunensis, based on the nearly complete holotypic skeleton and referred specimens, all of which were discovered in the Cancha de Bochas Member of the Ischigualasto Formation in northwestern Argentina. The lightly built skull has a slightly enlarged external naris and a spacious antorbital fossa with a prominent, everted dorsal margin and internal wall lacking any pneumatic extensions into surrounding bones. The tall quadrate is lapped along its anterior margin by the long, slender ventral process of the squamosal, and the lower jaw has a mid-mandibular joint between a tongue-shaped splenial process and a trough in the angular. All but the posterior-most maxillary and dentary crowns have a basal constriction, and the marginal denticles are larger and oriented more vertically than in typical theropod serrations. Rows of rudimentary palatal teeth are present on the pterygoid. Vertebral centra are hollow, although not demonstrably pneumatized,and all long bones have hollow shafts. The radius and ulna are more robust, the manus proportionately shorter, and the manual unguals less recurved than in the contemporaneous basal theropod Eodromaeus murphi. An outstanding feature of the manus of Eoraptor is the twisted shaft of the first phalanx of the pollex, which deflects medially the tip of the ungual as in basal sauropodomorphs. The long bones of the hind limb have more robust shafts than those of Eodromaeus, although in both genera the tibia remains slightly longer than the femur.

Resumen - Describimos el sauropodomorfo basal Eoraptor lunensis basados en el esqueleto prácticamente completo del holotipo y especímenes referidos, todos ellos descubiertos en el Miembro Cancha de Bochas de la Formaci ón Ischigualasto, en el noroeste de Argentina. El grácil cráneo tiene las narinas externas ligeramente agrandadas, una amplia fosa antorbital con un margen dorsal prominente y evertido, y ausencia de extensiones neumáticas en los huesos circundantes. El alto cuadrado presenta todo su margen anterior solapado por el delgado proceso ventral del escamoso y la mandíbula tiene una junta medial entre un proceso linguoide del esplenial y un canal en el angular. Todas las coronas dentarias y maxilares, menos las más posteriores, tienen una constricci ón basal y los dentículos marginales son largos y orientados más verticalmente que en el aserrado típico de los terópodos. El pterigoideo tiene filas de dientes palatales rudimentarios. Los centros de las vértebras son huecos, aunque no demostrablemente neumatizados, y todos los huesos largos tienen las di íafisis huecas. El radio y la ulna son más robustos, la mano proporcionalmente corta y los ungueales manuales menos recurvados que en el contemporáneo terópodo basal Eodromaeus murphi. Una característica sobresaliente de la mano de Eoraptor es la rotaci ón de la primera falange del pulgar, que desvía medialmente la punta del ungueal como en los sauropodomorfos basales. Los huesos largos de las piernas tienen di áfisis más robustas que aquellas de Eodromaeus, aunque en ambos géneros la tibia es ligeramente más larga que el fémur.

Asperoris mnyama, a New Archisauriform from the Middle Triassic of Tanzania

Nesbitt, S. J., Butler, R. J., and D. J. Gower. 2013. A New Archosauriform (Reptilia: Diapsida) from the Manda Beds (Middle Triassic) of Southwestern Tanzania. PLoS ONE 8(9): e72753. doi:10.1371/journal.pone.0072753

Abstract

Background

Archosauria and their closest relatives, the non-archosaurian archosauriforms, diversified in the Early and Middle Triassic, soon after the end-Permian extinction. This diversification is poorly documented in most Lower and Middle Triassic rock sequences because fossils of early groups of archosauriforms are relatively rare compared to those of other amniotes. The early Middle Triassic (? late Anisian) Manda beds of southwestern Tanzania form an exception, with early archosaur skeletons being relatively common and preserved as articulated or associated specimens. The Manda archosaur assemblage is exceptionally diverse for the Middle Triassic. However, to date, no non-archosaurian archosauriforms have been reported from these rocks.

Methodology/Principal Findings

Here, we name a new taxon, Asperoris mnyama gen. et sp. nov., from the Manda beds and thoroughly describe the only known specimen. The specimen consists of a well-preserved partial skull including tooth-bearing elements (premaxilla, maxilla), the nasal, partial skull roof, and several incomplete elements. All skull elements are covered in an autapomorphic highly rugose sculpturing. A unique combination of character states indicates that A. mnyama lies just outside Archosauria as a stem archosaur within Archosauriformes, but more precise relationships of A. mnyama relative to other early archosauriform clades (e.g., Erythrosuchidae) cannot be determined currently.

Conclusions/Significance

Asperoris mnyama is the first confirmed non-archosaurian archosauriform from the Manda beds and increases the morphological and taxonomic diversity of early archosauriforms known from the Middle Triassic. The direct association of A. mnyama with species referable to Archosauria demonstrates that non-archosaurian archosauriforms were present during the rise and early diversification of Archosauria. Non-archosaurian archosauriforms and archosaurs co-occur in fossil reptile assemblages across Pangaea from the late Early Triassic to the end of the Late Triassic.

The Problem of Dinosaur Origins: Integrating Three Approaches to the Rise of Dinosauria

An excellent essay looking on depth at the question of dinosaur origins. I think the ideas put forth are worthy of dicussion and will be heavily debated, especially since it is written from a North American perspective.

Padian, K., 2013. The problem of dinosaur origins: integrating three approaches to the
rise of Dinosauria. Earth and Environmental Science Transactions of the Royal Society of
Edinburgh First View Article. DOI: http://dx.doi.org/10.1017/S1755691013000431

Abstract - The problem of the origin of dinosaurs has historically had three dimensions. The first is the question of whether Dinosauria is monophyletic, and of its relationships to other archosaurs. This
question was plagued from the beginning by a lack of relevant fossils, an historical burden of confusing taxonomic terms and a rudimentary approach to devising phylogenies. The second dimension concerns the functional and ecological adaptations that differentiated dinosaurs from other archosaurs, a question also marred by lack of phylogenetic clarity and testable biomechanical hypotheses. The third dimension comprises the stratigraphic timing of the origin of dinosaurian groups with respect to each other and to related groups, the question of its synchronicity among various geographic regions, and some of the associated paleoenvironmental circumstances. None of these dimensions alone answers the question of dinosaur origins, and they sometimes provide conflicting implications. Since Dinosauria was named, one or another set of questions has historically dominated academic discussion and research. Paradigms have shifted substantially in recent decades, and current evidence suggests that we are due for more such shifts. I suggest two changes in thinking about the beginning of the “Age of Dinosaurs”: first, the event that we call the (phylogenetic) origin of dinosaurs was trivial compared to the origin of Ornithodira; and second, the “Age of Dinosaurs” proper did not begin until the Jurassic. Re-framing our thinking on these issues will improve our understanding of clade dynamics, timing of macroevolutionary events, and the effects of Triassic climate change on terrestrial vertebrates.

Reintroducing the Phytosaur Genus Machaeoroprosopus

I had posted about the taxonomic problem caused by the loss of the holotype specimen Machaeroprosopus validus before with a plea for people to help look for the specimen.  Come to find out a careful reading of the literature and the ICZN demonstrates that the specimen is not as important as previously believed regarding the taxonomic status of the name Machaeroprosopus. It will take awhile for Triassic and phytosaur workers to get used to using the name again and I am sure that some will just flat out refuse, but according to the ICZN the name Machaeoroprosopus is the proper one if the holotype specimen of "Belodon" buceros is truly diagnosable and if the other nominal species of "Pseudopalatus" are referable to the same genus represented by "B." buceros.

Parker, W. G., Hungerbühler, A., and J. W. Martz. 2013. The taxonomic status of the phytosaurs (Archosauriformes) Machaeroprosopus and Pseudopalatus from the Late Triassic of the western United States. Earth and Environmental Science Transactions of the Royal Society of Edinburgh First View Article. DOI: http://dx.doi.org/10.1017/S1755691013000339

Abstract - The genus Machaeroprosopus has long been considered invalid because the type specimen of the Late Triassic phytosaur species, M. validus, has been lost. Re-examination of the primary literature regarding the establishment of the Late Triassic phytosaur genus Machaeroprosopus demonstrates that M. buceros is the correct type species, not M. validus. Thus, the genus level name Machaeroprosopus has priority over the genera Pseudopalatus and Arribasuchus and all nominal species should be reassigned. Reassignment of these species to Machaeroprosopus satisfies the requirements of the International Code of Zoological Nomenclature (ICZN) and preserves historical context. The name Pseudopalatinae is retained as the valid clade name for these phytosaurs because its usage falls outside of the ICZN.

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

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.

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

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.

Life In the Triassic: Douglas Henderson

Great slide show of Douglas Henderson's Triassic artwork with a jazzy backing soundtrack. Keep the volume down a bit if you are at work.

http://www.youtube.com/watch?v=sdhhME-Qq7I&feature=c4-overview&list=UU6bQArLwtjMYTzbLjCb7uTg