New Triassic Trackway from Switzerland

Cavin, L., Avanzini, M., Bernardi, M., Piuz, A., Proz, P.-A., Meister, C., Boissonnas, J., and C. A. Meyer. 2012. New vertebrate trackway from the autochthonous cover of the Aiguilles Rouges Massif and reevaluation of the dinosaur record in the Valais, SW Switzerland. Swiss Journal of Palaeontology [online first] DOI: 10.1007/s13358-012-0040-0

Abstract - A new tracksite located in the Mesozoic autochthonous series covering the Aiguilles Rouges Massif, circa 7 km to the NNE of the tracksite of the Vieux Emosson, is briefly described. The trampled bed is most likely coeval with the outcrop in the Vieux Emosson area. Two poorly preserved quadrupedal trackways, almost parallel, measure 9.8 and 8 m in length, respectively. They are referred to the Chirotheriidae ABEL, 1835 form-family. A short and well-preserved quadrupedal trackway, composed of two manus-pes couples, is assigned to Chirotherium cf. barthii KAUP, 1835. A reinterpretation of the Vieux Emosson ichnotaxa reveals that most tracks, if not all, belong to indeterminate chirotheriid and that no clear evidence of dinosaur footprints is observed. The trampled bed of the cover of the Aiguilles Rouges Massif probably forms a megatracksite, which is Early or Middle Triassic in age.  

Could it Be? An Non-Archosaurian Archosauriform that is Actually a Dinosaur?

The past eight years have seen quite a few cases where purported Triassic dinosaurs actually turned out to be non-dinosaurian archosauriforms...Revueltosaurus, Shuvosaurus, Azendohsaurus... finally the dinosaurs get one back. Moreover there are no Jurassic or Chinese phytosaur specimens. 

Barrett, P. M., and X. Xu. 2012. The enigmatic reptile Pachysuchus imperfectus Young, 1951 from the lower Lufeng Formation (Lower Jurassic) of Yunnan, China. Vertebrata PalAsiatica 50:151-159. [Free download here]

Abstract - Phytosaurs are generally considered to have become extinct at the end of the Triassic Period, but several records have suggested that they survived into the basal Jurassic in Europe and Asia. The Asian record consists of Pachysuchus imperfectus from the lower Lufeng Formation (?Hettangian-Sinemurian) of Yunnan, China. However, this specimen differs from phytosaurs in numerous aspects and is more likely a poorly preserved, indeterminate sauropodomorph dinosaur skull. The referred specimens of this species are also regarded as indeterminate, thereby removing the post-Triassic record of phytosaurs from Asia. The European records of Jurassic phytosaurs are also shown to be doubtful, suggesting that this clade was restricted to the Late Triassic. 

Neotype Proposal for Anchisaurus polyzelus

Galton, P.M. 2012. Case 3561 Anchisaurus Marsh, 1885 (Dinosauria, Sauropodomorpha): proposed conservation of usage by designation of a neotype for its type species Megadactylus polyzelus Hitchcock, 1865. Bulletin of Zoological Nomenclature 69 (1): 44-50.



Abstract - The purpose of this application, under Article 75.5 of the Code, is to conserve the usage of the name Anchisaurus Marsh, 1885 (Lower Jurassic, Connecticut Valley, northeastern U.S.A.) that is based on Megadactylus polyzelus Hitchcock, 1865. It is proposed to replace the fragmentary and non-diagnostic holotype of M. polyzelus with a diagnostic neotype, an almost complete skull and skeleton (YPM 1883, holotype of A. colurus Marsh, 1891). This specimen has formed the basis for the concept of Anchisaurus, the first basal sauropodomorph genus from the U.S.A. and still the best represented from there since it was illustrated by Marsh (1892, 1893), and of A. polyzelus since it was illustrated by Galton (1976). Anchisaurus is the basis for ANCHISAURIDAE Marsh, 1885, the first basal sauropodomorph family to be named, and for the Anchisauria Galton & Upchurch, 2004.

First Multi-taxic Multi-component Ornithischian and Sauropodomorph Dinosaur Bonebed from the Upper Triassic of North America

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Just kidding...

Happy April 1 everyone!

Paleohistological Estimation of Bone Growth Rate in Extinct Archosaurs

Cubo, J., LeRoy, N., Martinez-Maza, C., and L. Montes. 2012. Paleohistological estimation of bone growth rate in extinct archosaurs. Paleobiology 38:335-339. doi: http://dx.doi.org/10.1666/08093.1

Abstract - The clade Archosauria contains two very different sister groups in terms of diversity (number of species) and disparity (phenotypic variation): Crurotarsi (taxa more closely related to crocodiles than to birds) and Ornithodira (pterosaurs and dinosaurs including birds). The extant species of Crurotarsi may constitute a biased sample of past biodiversity regarding growth patterns and metabolic rates. Bone histological characters can be conserved over hundreds of millions of years in the fossil record and potentially contain information about individual age at death, age at sexual maturity, bone growth rates, and basal metabolic rates of extinct vertebrates. Using a sample of extant amniotes, we have constructed a paleobiological model to estimate bone growth rate from bone histological traits. Cross-validation tests show that this model is reliable. We then used it to estimate bone growth rates in a sample of extinct archosaurs including Crurotarsi and Ornithodira. After testing for phylogenetic signal, optimization of femoral growth rates through squared change parsimony onto a time-calibrated tree of amniotes shows two divergent evolutionary trends: whereas bone growth rates increase from the last common ancestor of Ornithodira to extant birds, they decrease from the last common ancestor of Crurotarsi to extant crocodiles. However, we conclude, on the basis of recent evidence for unidirectional airflow in the lungs of alligators, that crocodiles may have retained the capacity of growing at high rates.

Vegetation History and Climate Change Across the Tr/J Boundary

Bonis, N. R., and W. M. Kürschner. 2012. Vegetation history, diversity patterns, and climate change across the Triassic/Jurassic boundary. Paleobiology 38:240-264. doi: http://dx.doi.org/10.1666/09071.1

Abstract - High-resolution palynological data sets from shallow marine Triassic-Jurassic (Tr/J) boundary beds of two principal sections in Europe (Hochalplgraben in Austria and St. Audrie's Bay in the United Kingdom) were analyzed to reconstruct changes in vegetation, biodiversity, and climate. In Hochalplgraben, a hardwood gymnosperm forest with conifers and seed ferns is replaced by vegetation with dominant ferns, club mosses and liverworts, which concurs with an increased diversification of spore types during the latest Rhaetian. Multivariate statistical analysis reveals a trend to warmer and wetter conditions across the Tr/J boundary in Hochalplgraben. The vegetation changes in St. Audrie's Bay are markedly different. Here, a mixed gymnosperm forest is replaced by monotonous vegetation consisting mainly of Cheirolepidiaceae (80–100%). This change is caused by a transition to a warmer and more arid climate. The observed diversity decrease in St. Audrie's Bay affirms this interpretation. Although both sections show major vegetation changes, neither of them demonstrates a distinctive floral mass extinction. A compilation of Tr/J boundary sections across the world demonstrates the presence of Cheirolepidiaceae-dominated forests in the Pangaean interior and increases in abundance of spore-producing plants adjacent to the Tethys Ocean. We propose that the non-uniform vegetation changes reflected in the Tr/J palynological records are the result of environmental changes caused by Central Atlantic Magmatic Province volcanism. The increase in greenhouse gases caused a warmer climate and an enhanced thermal contrast between the continent and the seas. Consequently, the monsoon system got stronger and induced a drier continental interior and more intensive rainfall near the margins of the Tethys Ocean.

Postcranial Skeletal Pneumaticity in Triassic Archosaurs

Butler, R. J., Barrett, P. M., and D. J. Gower. 2012. Reassessment of the evidence for postcranial skeletal pneumaticity in Triassic archosaurs, and the early evolution of the avian respiratory system. PLoS ONE 7(3): e34094. doi:10.1371/journal.pone.0034094


Abstract - Uniquely among extant vertebrates, birds possess complex respiratory systems characterised by the combination of small, rigid lungs, extensive pulmonary air sacs that possess diverticula that invade (pneumatise) the postcranial skeleton, unidirectional ventilation of the lungs, and efficient crosscurrent gas exchange. Crocodilians, the only other living archosaurs, also possess unidirectional lung ventilation, but lack true air sacs and postcranial skeletal pneumaticity (PSP). PSP can be used to infer the presence of avian-like pulmonary air sacs in several extinct archosaur clades (non-avian theropod dinosaurs, sauropod dinosaurs and pterosaurs). However, the evolution of respiratory systems in other archosaurs, especially in the lineage leading to crocodilians, is poorly documented. Here, we use mCT-scanning to investigate the vertebral anatomy of Triassic archosaur taxa, from both the avian and crocodilian lineages as well as non-archosaurian diapsid outgroups. Our results confirm previous suggestions that unambiguous evidence of PSP (presence of internal pneumatic cavities linked to the exterior by foramina) is found only in bird-line (ornithodiran) archosaurs. We propose that pulmonary air sacs were present in the common ancestor of Ornithodira and may have been subsequently lost or reduced in some members of the clade (notably in ornithischian dinosaurs). The development of these avian-like respiratory features might have been linked to inferred increases in activity levels among ornithodirans. By contrast, no crocodile-line archosaur (pseudosuchian) exhibits evidence for unambiguous PSP, but many of these taxa possess the complex array of vertebral laminae and fossae that always accompany the presence of air sacs in ornithodirans. These laminae and fossae are likely homologous with those in ornithodirans, which suggests the need for further investigation of the hypothesis that a reduced, or non-invasive, system of pulmonary air sacs may be have been present in these taxa (and secondarily lost in extant crocodilians) and was potentially primitive for Archosauria as a whole.

Taphonomy of an Upper Triassic Rhynchosaur Bonebed From India

Mukherje, D. and  & S. Ray. 2012. Taphonomy of an Upper Triassic vertebrate bonebed: A new rhynchosaur (Reptilia; Archosauromorpha) accumulation from India. Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication) http://dx.doi.org/10.1016/j.palaeo.2012.03.010


Abstract - The Upper Triassic Tiki Formation of India is a rich storehouse of varied vertebrate fossil assemblages. So far, there is no information on taphonomic signatures of the Tiki vertebrate assemblages in comparison to that of other fossiliferous horizons of India. We report a new, low diversity, mono-dominant, multitaxic vertebrate accumulation where rhynchosaurs constitute the dominant component. The formation of the rhynchosaur bonebed is attributed to biological aggregation with a hydraulic overprint resulting in a mixed-origin concentration. Other taxa include rauisuchid, phytosaur, small indeterminate archosaur and cynodonts. Taphonomic study based on 617 skeletal specimens of rhynchosaurs collected from nine sites within an area of about 250x217 sq m shows that most of the specimens are disarticulated and disassociated but in close spatial proximity to one another; some are associated specimens and few are articulated. About 13 to 20 individuals of rhynchosaur at different ontogenetic stages are estimated from the specimens collected, suggesting gregarious behaviour, possibly herding. These specimens show varying degree of weathering, breakage, encrustation, abrasion and deformation. The bonebed is preserved within the Tiki red mudstone unit and is found in association with paleosol profiles, suggesting prolonged subaerial exposure. Spatial distribution and relative bone frequencies show differential susceptibility of the skeletal specimens to fluvial transport. 55.4% of the collected skeletal specimens belonged to Voorhies Group I, whereas 12.4% and 24% constituted Voorhies Group II and III respectively, and 8.2% of the collected specimens belonged to the intermediate group I and II. It appears that the animals concentrated in the vicinity of the water sources during prolonged period of aridity and died possibly during high seasonal rainfall that resulted in a major flood event. Subsequently, the soft tissues decomposed, and the skeletons suffered prolonged subaerial exposure when the water receded leading to disarticulation and fragmentation followed by minor dispersion by low velocity water currents. This resulted in segregation of skeletal specimens, which were gradually covered by mud deposited during later flooding events. Based on the known flora and fauna, the Tiki Upper Triassic ecosystem is reconstructed for the first time. In the aquatic ecosystem, the metoposaurid labyrinthodonts occupied the top of the food pyramid together with the semi-aquatic parasuchids, which occupied an ecological niche similar to that of the present day crocodilians. The abundance of herbivorous rhynchosaurs at the base with few large and carnivorous rauisuchids and parasuchids at the top suggest a trophic structure similar to that of a modern day terrestrial ecosystem.

Revised Phylogeny of Basal Turtles

Anquetin, J. 2012. Reassessment of the phylogenetic interrelationships of basal turtles (Testudinata). Journal of Systematic Palaeontology 10:3-45. doi: http://dx.doi.org/10.1080/14772019.2011.558928


Abstract - Recent discoveries from the Late Triassic and Middle Jurassic have significantly improved the fossil record of early turtles. These new forms offer a unique opportunity to test the interrelationships of basal turtles. Nineteen fossil species are added to the taxon sample of the most comprehensive morphological phylogenetic analysis of the turtle clade. Among these additional species are recently discovered forms (e.g. Odontochelys semitestacea, Eileanchelys waldmani, Condorchelys antiqua), taxa generally omitted from previous analyses (e.g. chengyuchelyids, Sichuanchelys chowi) and species included in a phylogenetic analysis for the first time (Naomichelys speciosa and Siamochelys peninsularis). The coding of several characters is reassessed in the light of recent observations, but also in order to reduce unwarranted assumptions on character and character state homologies. Additional characters from previous analyses, as well as five new ones, are also included, resulting in a data matrix of 178 characters scored for 86 turtle species and seven fossil outgroups. The dataset resolves the relationships of most newly included taxa, with the exception of S. chowi and ‘Chengyuchelys’ dashanpuensis. The phylogenetic placement of Heckerochelys romani, Condorchelys antiqua and Eileanchelys waldmani as stem turtles more derived than Kayentachelys aprix but more basal than Meiolania platyceps and Mongolochelys efremovi is corroborated. The relationships of chengyuchelyids remain unclear and they are unstable with respect to stem turtles. In contrast to previous analyses, Arundelemys dardeni is placed within pleurosternids and Siamochelys peninsularis falls within xinjiangchelyids. Perhaps the most salient conclusion of the present study is the placement of Naomichelys speciosa as a basal member of a clade uniting meiolaniids, Mongolochelys efremovi and Otwayemys cunicularius. This clade of rather large stem turtles had a worldwide spread during the Mesozoic at least, and persisted until the Pleistocene with meiolaniids.

Further Evidence of Burrowing in Procolophonid Parareptiles

MacDougall, M. J., Modesto, S. P., and J. Botha-Brink. 2012. The postcranial skeleton of the Early Triassic parareptile Sauropareion anoplus, with a discussion of possible life history. Acta Palaeontologica Polonica in press. Available online 27 Feb 2012 doi: http://dx.doi.org/10.4202/app.2011.0099.

Abstract - The skeletal anatomy of the Early Triassic (Induan) procolophonid reptile Sauropareion anoplus is described on the basis of three partial skeletons from Vangfontein, Middelburg District, South Africa. Together these three specimens preserve the large majority of the pectoral and pelvic girdles, articulated forelimbs and hindlimbs, and all but the caudal portion of the vertebral column, elements hitherto undescribed. Our phylogenetic analysis of the Procolophonoidea is consonant with previous work, positing S. anoplus as the sister taxon to a clade composed of all other procolophonids exclusive of Coletta seca. Previous studies have suggested that procolophonids were burrowers, and this seems to have been the case for S. anoplus, based on comparisons with characteristic skeletal anatomy of living digging animals, such as the presence of a spade-shaped skull, robust phalanges, and large unguals.

Earliest Evidence of Ovoviviparity in Coelocanths

Wen, W., Zhang, Q.-Y., Hu, S.-X., Benton, M. J., Zhou, C.-Y., Tao, X., Yuan, H.-J., and Z.-Q., Chen. 2012. Coelacanths from the Middle Triassic Luoping Biota, Yunnan, South China, with the earliest evidence of ovoviviparity. Acta Palaeontologica Polonica in press. Available online 08 Mar 2012 doi: http://dx.doi.org/10.4202/app.2011.0066

Abstract - The fossil record of coelacanths is patchy, with very few taxa known from the Triassic of Asia. We report here two new genera and species of coelacanths from the Luoping Biota, a recently found site of exceptional fossil preservation from Yunnan, South China. The first new taxon, Luopingcoelacanthus eurylacrimalis, is based on four specimens, which together show most aspects of the anatomy. One specimen shows two small coelacanths inside the ventral portion of the abdominal cavity, and these are interpreted as intrauterine embryos, close to birth size, based on comparisons with previously reported embryos of the fossil coelacanths Rhabdoderma and Undina, and the extant genus Latimeria. Our new find extends the evidence for ovoviviparity in coelacanths back from the Late Jurassic to the Middle Triassic. The second new taxon, Yunnancoelacanthus acrotuberculatus, is based on one specimen, and differs from Luopingcoelacanthus in the dentary, lachrymojugal, number of rays of the first dorsal fin, and especially in the ornament on dermal bones and scales. A cladistic analysis shows that the new taxa are closest relatives to the derived clade Latimerioidei. The relatively high diversity of coelacanths in the Early Triassic, and adaptations of living Latimeria to low-oxygen conditions, suggests that the group may have included ‘disaster taxa’ that benefited from anoxic and dysoxic ocean conditions in the aftermath of the end-Permian mass extinction.

Early Evolution of Postcranial Skeletal Pneumaticity in Sauropodomorph Dinosaurs

I don't think I've posted this paper previously, but it has been in press for a year...

Yates, A. M., Wedel, M. J., and M. F. Bonnan. 2012. The early evolution of postcranial skeletal pneumaticity in sauropodomorph dinosaurs. Acta Palaeontologica Polonica 57:85-100.  

doi: http://dx.doi.org/10.4202/app.2010.0075

Abstract - Postcranial skeletal pneumaticity (PSP) is present in a range of basal sauropodomorphs spanning the basal sauropodomorph—sauropod transition. We describe the PSP of five taxa, Plateosaurus engelhardti, Eucnemesaurus fortis, Aardonyx celestae, Antetonitrus ingenipes, and an unnamed basal sauropod from Spion Kop, South Africa (hereafter referred to as the Spion Kop sauropod). The PSP of Plateosaurus is apparently sporadic in its occurrence and has only been observed in very few specimens, in which it is of very limited extent, affecting only the posterior cervical vertebrae and possibly the mid dorsals in one specimen. The PSP of Eucnemesaurus, Aardonyx, Antetonitrus, and the Spion Kop sauropod consists of subfossae (fossa within-fossa structures) that excavate the vertices of the posterior infradiapophyseal fossae of the posterior dorsal vertebrae. These subfossae range from simple shallow depressions (Eucnemesaurus) to deep, steepsided, internally subdivided and asymmetrically developed chambers (Antetonitrus). The middle and anterior dorsal vertebrae of these taxa lack PSP, demonstrating that abdominal air sacs were the source of the invasive diverticula. The presence of pneumatic features within the infradiapophyseal fossae suggest that the homologous fossae of more basal saurischians and dinosauriforms were receptacles that housed pneumatic diverticula. We suggest that it is probable that rigid non-compliant lungs ventilated by compliant posterior air sacs evolved prior to the origination of Dinosauria.

Panchetocynodon damodarensis, a New Cynodont from the Lower Triassic of India

Das, D. P., and A. Gupta. 2012. New cynodont record from the lower Triassic Panchet Formation, Damodar valley. Earth and Environmental Science Journal of the Geological Society of India Volume 79, Number 2, 175-180 DOI: 10.1007/s12594-012-0022-2


Abstract - This paper reports the find of a new non-mammalian cynodont from the Lower Triassic Panchet Formation of the Damodar valley, West Bengal, India. The fossil, recovered from a clay pellet rich calcareous sandstone bed, is a part of left lower jaw having five post canines that are damaged to various extents. A combination of mammal-like advanced characters such as much enlarged dentary, reduced post dentary bones, high coronoid process, large masseteric fossa, each post canine with a large central cusp flanked by a distal and a mesial accessory cusps with two additional lingually positioned cingular cusps, incipient root division and clearly demarcated crown-root juncture prompted to erect a new taxon Panchetocynodon damodarensis gen. et sp. nov.

Hind limb osteology of Gracilisuchus stipanicicorum

Lecuona, A., and J. B. Desojo 2011. Hind limb osteology of Gracilisuchus
stipanicicorum (Archosauria: Pseudosuchia). Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 102, 105–128.


Abstract - Gracilisuchus stipanicicorum Romer, 1972, from the Middle-Late Triassic of the Ischigualasto–Villa Unio´n Basin of Argentina, is an extinct pseudosuchian archosaur on the stem to Crocodylomorpha. The pelvic girdle and hind limb anatomy of a referred specimen of Gracilisuchus stipanicicorum is described and compared with that from a broad range of archosauriform taxa, including basal members such as crurotarsans and basal ornithodirans. The description of this specimen reveals new information on the anatomy of the pelvic girdle and hind limb of Gracilisuchus, through a detailed examination of some anatomical regions barely or not previously described, as well as reinterpretations of previous features. The phylogenetic affinities of Gracilisuchus within the Archosauria remain to be tested, but Gracilisuchus shares two putative synapomorphies with some non-crocodyliform crocodylomorphs, providing tentative support for the monophyly of Sphenosuchia (e.g., Sereno & Wild 1992; Wu & Chatterjee 1993) and the close relationship of Gracilisuchus to that clade. These characteristics are: (i) the morphology and poor development of the femoral fourth trochanter, closely resembling the condition of Pseudhesperosuchus and Trialestes; and (ii) a poor anterior development of the femoral head, shared with Pseudhesperosuchus. On the other hand there are characters that reject the inclusion of Gracilisuchus within Crocodylomorpha (Nesbitt 2011), such as the absence of an imperforated acetabulum, and that rather suggests a sister-taxon position to Crocodylomorpha.