Field of Science

Systematics of Putative Euparkeriids from the Triassic of China

Sookias, R. B., Sullivan, C., Liu, J., and R. J. Butler. 2014. Systematics of putative euparkeriids (Diapsida: Archosauriformes) from the Triassic of China. PeerJ 2:e658 doi:http://dx.doi.org/10.7717/peerj.658

Abstract - The South African species Euparkeria capensis is of great importance for understanding the early radiation of archosauromorphs (including archosaurs) following the Permo–Triassic mass extinction, as most phylogenetic analyses place it as the sister taxon to crown group Archosauria within the clade Archosauriformes. Although a number of species from Lower–Middle Triassic deposits worldwide have been referred to the putative clade Euparkeriidae, the monophyly of Euparkeriidae is controversial and has yet to be demonstrated by quantitative phylogenetic analysis. Three Chinese taxa have been recently suggested to be euparkeriids: Halazhaisuchus qiaoensis, ‘Turfanosuchus shageduensis’, and Wangisuchus tzeyii, all three of which were collected from the Middle Triassic Ermaying Formation of northern China. Here, we reassess the taxonomy and systematics of these taxa. We regard Wangisuchus tzeyii as a nomen dubium, because the holotype is undiagnostic and there is no convincing evidence that the previously referred additional specimens represent the same taxon as the holotype. We also regard ‘Turfanosuchus shageduensis’ as a nomen dubium as we are unable to identify any diagnostic features. We refer the holotype to Archosauriformes, and more tentatively to Euparkeriidae. Halazhaisuchus qiaoensis and the holotype of 'Turfanosuchus shageduensis’ are resolved as sister taxa in a phylogenetic analysis, and are in turn the sister taxon to Euparkeria capensis, forming a monophyletic Euparkeriidae that is the sister to Archosauria+Phytosauria. This is the first quantitative phylogenetic analysis to recover a non-monospecific, monophyletic Euparkeriidae, but euparkeriid monophyly is only weakly supported and will require additional examination. Given their similar sizes, stratigraphic positions and phylogenetic placement, the holotype of ‘Turfanosuchus shageduensis’ may represent a second individual of Halazhaisuchus qiaoensis, but no apomorphies or unique character combination can be
identified to unambiguously unite the two. Our results have important implications for understanding the species richness and palaeobiogeographical distribution of early archosauriforms.

Silesaurid-Herrerasaurid-Neotheropod Assemblage from the Late Triassic of Poland

This is currently free from the Palaeontology Online website.

Niedźwiedzki, G., Brusatte, S. L., Sulej, T., and R. J. Butler. 2014. Basal dinosauriform and theropod dinosaurs from the mid–late Norian (Late Triassic) of Poland: implications for Triassic dinosaur evolution and distribution. Palaeontology 57(6): 1121–1142 DOI: 10.1111/pala.12107
 
Abstract - The rise of dinosaurs during the Triassic is a widely studied evolutionary radiation, but there are still many unanswered questions about early dinosaur evolution and biogeography that are hampered by an unevenly sampled Late Triassic fossil record. Although very common in western North America and parts of South America, dinosaur (and more basal dinosauriform) remains are relatively rare in the Upper Triassic deposits of Europe, making any new discoveries critically important. One of the most diverse dinosauriform assemblages from Europe comes from the Poręba site in Poland, a recently described locality with exposures of the Zbąszynek Beds, which have a palynomorph assemblage characteristic for the mid–late Norian in the biostratigraphic schemes of the Germanic Basin. Using a synapomorphy-based approach, we evaluate several isolated dinosauriform specimens from Poręba. This assemblage includes a silesaurid, a herrerasaurid and remains of another type of theropod (potentially a neotheropod). The Poręba herrerasaurid is the first record of this rare group of primitive dinosaurs from Europe and one of the youngest records worldwide, whereas the silesaurid is the youngest record of a silesaurid from Europe. These findings indicate that silesaurids persisted alongside true dinosaurs into the mid–late Norian of Europe and that silesaurid–herrerasaurid–neotheropod assemblages (which are also known from the Norian of North America, at low latitudes) were more widespread geographically and latitudinally than previously thought. Silesaurid–herrerasaurid–neotheropod assemblages may have been a common ecological structuring of dinosaurs during their early evolution, and their widespread distribution may indicate weak palaeolatitudinal controls on early dinosaur biogeography during the latest Triassic.

Dr. Ruth L. Elder - July 22, 1954 – Nov. 4, 2014

Dr. Ruth L. (Jessie) Elder passed away earlier this month at the age of 60.  Dr. Elder is best known in the vertebrate paleontology community for her work on the Triassic vertebrate fauna from the Dockum Group near Otis Chalk, Texas. The purported rhynchosaurian Otischalkia elderae is named in her honor.

Dr. Elder's obituary can be viewed here.

Garjainia madiba, a new Erythrosuchid Archosauriform from the Early Triassic of South Africa

Gower, D. J., Hancox, P. J., Botha-Brink, J., Sennikov, A. G., and R. J. Butler. 2014. A New Species of Garjainia Ochev, 1958 (Diapsida: Archosauriformes: Erythrosuchidae) from the Early Triassic of South Africa. PLoS ONE 9(11): e111154. doi:10.1371/journal.pone.0111154

Abstract -
A new species of the erythrosuchid archosauriform reptile Garjainia Ochev, 1958 is described on the basis of disarticulated but abundant and well-preserved cranial and postcranial material from the late Early Triassic (late Olenekian) Subzone A of the Cynognathus Assemblage Zone of the Burgersdorp Formation (Beaufort Group) of the Karoo Basin of South Africa. The new species, G. madiba, differs from its unique congener, G. prima from the late Olenekian of European
Russia, most notably in having large bony bosses on the lateral surfaces of the jugals and postorbitals. The new species also has more teeth and a proportionately longer postacetabular process of the ilium than G. prima. Analysis of G. madiba bone histology reveals thick compact cortices comprised of highly vascularized, rapidly forming fibro-lamellar bone tissue, similar to Erythrosuchus africanus from Subzone B of the Cynognathus Assemblage Zone. The most notable differences between the two taxa are the predominance of a radiating vascular network and presence of annuli in the limb bones of G. madiba. These features indicate rapid growth rates, consistent with data for many other Triassic archosauriforms, but also a high degree of developmental plasticity as growth remained flexible. The diagnoses of Garjainia and of Erythrosuchidae are addressed and revised. Garjainia madiba is the geologically oldest erythrosuchid known from the Southern Hemisphere, and demonstrates that erythrosuchids achieved a cosmopolitan biogeographical distribution by the end of the Early Triassic, within five million years of the end-Permian mass extinction event. It provides new insights into the diversity of the Subzone A vertebrate assemblage, which partially fills a major gap between classic ‘faunal’ assemblages from the older Lystrosaurus Assemblage Zone (earliest Triassic) and the younger Subzone B of the Cynognathus Assemblage Zone (early Middle Triassic).

Garjainia madiba reconstruction by Mark Witton

Significance of Skeletal Variation in the Late Triassic Dinosauriform Silesaurus opolensis

Piechowski, P., Tałanda, M., and J. Dzik. 2014. Skeletal variation and ontogeny of the Late Triassic Dinosauriform Silesaurus opolensis. Journal of Vertebrate Paleontology 34:1383-1393 DOI:10.1080/02724634.2014.873045

Abstract -
A principal component analysis (PCA) performed for a set of 24 measurements on 33 femora and 15 measurements on 20 ilia of Silesaurus opolensis from the early Late Triassic of Krasiejów, southern Poland, shows that this sample is highly variable but probably monospecific. Most of the morphological variation is concentrated in the muscle attachments and proportions of bones, which significantly change in both size and position during ontogeny. Despite the small sample size, femora of smaller individuals have less flattened shafts and a more sinusoidal appearance. In many large specimens, proximal parts of muscle tendons are ossified at their attachment site on femora and remain attached to the bone in the largest specimens. The specimens with attached ossifications are interpreted as mature females that were statistically larger than proposed males. It is suggested that ossifications developed in females under calcitonin control. The intrapopulation variability of ilia is high, but less dependant on ontogeny. The population represented by a few specimens from the lower level at Krasiejów may represent a different stage in the evolution of the species than that from the upper horizon.

Cartorhynchus lenticarpus, a New Basal Ichthyosauriform from the Lower Triassic of China

Amazing!

Motani, R., Jiang, D.-Y., Chen, G.-B., Tintori, A., Rieppel, O., Ji, C., and J.-D. Huang. 2014. A basal ichthyosauriform with a short snout from the Lower Triassic of China. Nature (article preview). doi:10.1038/nature13866

Abstract -
The incompleteness of the fossil record obscures the origin of many of the more derived clades of vertebrates. One such group is the Ichthyopterygia, a clade of obligatory marine reptiles that appeared in the Early Triassic epoch, without any known intermediates. Here we describe a basal ichthyosauriform from the upper Lower Triassic (about 248 million years ago) of China, whose primitive skeleton indicates possible amphibious habits. It is smaller than ichthyopterygians and had unusually large flippers that probably allowed limited terrestrial locomotion. It also retained characteristics of terrestrial diapsid reptiles, including a short snout and body trunk. Unlike more derived ichthyosauriforms, it was probably a suction feeder. The new species supports the sister-group relationships between ichthyosauriforms and Hupehsuchia, the two forming the Ichthyosauromorpha. Basal ichthyosauromorphs are known exclusively from south China, suggesting
that the clade originated in the region, which formed a warm and humid tropical archipelago in the Early Triassic. The oldest unequivocal record of a sauropterygian is also from the same stratigraphic unit of the region.

Description of the Ornithosuchid Archosaurian Venaticosuchus rusconii from the Late Triassic of Argentina and the Phylogeny of the Ornithosuchidae

Von Baczko, M. B., Desojo, J. B., and D. Pol. 2014. Anatomy and phylogenetic position of Venaticosuchus rusconii Bonaparte, 1970 (Archosauria, Pseudosuchia), from the Ischigualasto Formation (Late Triassic), La Rioja, Argentina. Journal of Vertebrate Paleontology 34:1342-1356 DOI:10.1080/02724634.2014.860150

Abstract -
Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogenetic affinities. This clade currently comprises three taxa: Venaticosuchus rusconii and Riojasuchus tenuisceps, both from Argentina, and Ornithosuchus longidens, from Scotland. V. rusconii was erected on the basis of an incomplete skull with articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra.

Nundasuchus songeaensis, a New Archosauriform from the Middle Triassic of Tanzania and its Implications for the Phylogeny of the Archosauria

Nesbitt, S. J., Sidor, C. A., Angielczyk, K. D., Smith, R. M. H., and L. A. Tsuji. 2014. A new archosaur from the Manda beds (Anisian, Middle Triassic) of southern Tanzania and its implications for character state optimizations at Archosauria and Pseudosuchia. Journal of Vertebrate Paleontology 34:1357-1382 DOI:10.1080/02724634.2014.859622

Abstract -
The presence of early pseudosuchians and avemetatarsalians in Anisian beds of Africa demonstrates that the archosaur radiation was well underway by the beginning of the Middle Triassic. The rapid radiation produced a variety of forms, but many of the unique, well-diagnosed
Late Triassic clades (e.g., Aetosauria, Ornithosuchidae) lack diagnosable members from the Middle Triassic. Here, we introduce a new Middle Triassic archosaur, Nundasuchus songeaensis, gen. et sp. nov., with an unusual mix of apomorphic character states found within Pseudosuchia and just outside Archosauria. The holotype consists of partial skeleton, including representative postcranial elements and parts of the skull. We added Nundasuchus songeaensis, gen. et sp. nov., into the two most comprehensive early archosaur phylogenetic data sets available, and in both analyses the new taxon falls within Pseudosuchia. However, a number of plesiomorphic archosaurian character states (e.g., posterolaterally directed tuber of the calcaneum) optimize as local autapomorphies of the new taxon within Pseudosuchia in our analyses. Therefore, we tested alternative hypotheses of relationships for the new taxon by utilizing constraint trees. The analyses resulted in little change in the relationships and structure of other Triassic archosaur clades, but changed optimizations of certain character states and character support at the base of Pseudosuchia and Archosauria. Our analyses suggest that the
complex evolution of character-state changes at the base of Archosauria is inhibiting our understanding of the relationships of early Pseudosuchia and, in turn, Archosauria.

Principal Features of the Mammalian Nasal Cavity were Present in Triassic Eucynodonts

Ruf, I., Maier, W., Rodrigues, P. G., and C. L. Schultz. 2014. Nasal Anatomy of the Non-mammaliaform Cynodont Brasilitherium riograndensis (Eucynodontia, Therapsida) Reveals New Insight into Mammalian Evolution. The Anatomical Record 297: 2018–2030. DOI: 10.1002/ar.23022
Abstract - The mammalian nasal cavity is characterized by a unique anatomy with complex internal features. The evolution of turbinals was correlated with endothermic and macrosmatic adaptations in therapsids and in early mammals, which is still apparent in their twofold function (warming and moistening of air, olfaction). Fossil evidence for the transformation from the nonmammalian to the mammalian nasal cavity pattern has been poor and inadequate. Ossification of the cartilaginous nasal capsule and turbinals seems to be a feature that occurred only very late in synapsid evolution but delicate ethmoidal bones are rarely preserved. Here we provide the first µCT investigation of the nasal cavity of the advanced non-mammaliaform cynodont Brasilitherium riograndensis from the Late Triassic of Southern Brazil, a member of the sister-group of mammaliaforms, in order to elucidate a critical anatomical transition in early mammalian evolution. Brasilitherium riograndensis already had at least partially ossified turbinals as remnants of the nasoturbinal and the first ethmoturbinal are preserved. The posterior nasal septum is partly ossified and contributes to a mesethmoid. The nasal cavity is posteriorly expanded and forms a distinctive pars posterior (ethmoidal recess) that is ventrally separated from the nasopharyngeal duct by a distinct lamina terminalis. Thus, our observations clearly demonstrate that principal features of the mammalian nasal cavity were already present in the sister-group of mammaliaforms.

Panguraptor lufengensis, a New Coelophysoid Theropod Dinosaur from the Lower Jurassic of China

You, H.-L., Azuma, Y., Wang, T., Wang, Y.-M., and Z.-M. Dong. 2014. The first well-preserved coelophysoid theropod dinosaur from Asia. Zootaxa 3873:233–249.

Abstract - Previously reported coelophysoid material from Asia (excluding the Gondwanan territory of India) is limited to two specimens that comprise only limb fragments. This paper describes a new genus and species of coelophysoid, Panguraptor lufengensis, from the Lower Jurassic Lufeng Formation of Yunnan Province, China. The new taxon is represented by a well-preserved skeleton, including the skull and lower jaw, the presacral vertebral column and partial ribs, the right scapula, a partial forelimb, part of the pelvic girdle, and an almost complete hind limb. It is distinguished from other coelophysoid theropods by the unique combination of the following three character states: 1) diagonal (rostrodorsal-caudoventral) ridge on lateral surface of maxilla, within antorbital fossa, 2) elliptical, laterally facing fenestra caudodorsal to aforementioned diagonal ridge, and 3) hooked craniomedial corner of distal tarsal IV. Cladistic analysis recovers Panguraptor lufengensis deeply nested within Coelophysoidea as a member of Coelophysidae, and it is more closely related to Coelophysis than to “Syntarsus”. Panguraptor represents the first well-preserved coelophysoid theropod dinosaur from Asia, and provides fresh evidence supporting the hypothesis that terrestrial tetrapods tended to be distributed pan-continentally during the Early Jurassic.

Functional and Biomechanic Aspects of the Scapular Girdle and Forelimbs of Unaysaurus tolentinoi

Vargas-Peixoto, D., Stock Da-Rosa, Á, A., and M. A. G. França. 2014. Functional and biomechanic aspects of the scapular girdle and forelimbs of Unaysaurus tolentinoi Leal et al., 2004 (Saurischia: Sauropodomorpha). Journal of South American Earth Sciences. Accepted Manuscript. DOI: 10.1016/j.jsames.2014.09.024

Abstract -
 This study presents evidence about the biomechanics and forelimbs functionality of the basal sauropodomorph Unaysaurus tolentinoi (upper portion of the SM2 sequence, Santa Maria Supersequence, Upper Triassic from southern Brazil). Maximum and minimum motion angles were inferred in the joints, disregarding the presence and/or thickness of cartilage. Furthermore, processes and external structures of the bones were analyzed in attributing the functionality of forelimbs. Unaysaurus tolentinoi had well-developed grapple ability. However, the preserved elements and their osteological features are not conclusive about strictly bipedalism or quadrupedalism in U. tolentinoi.

Tachiraptor admirabilis and the Early Dispersal of Dinosaurs after the end-Triassic Extinction

Langer, M. C., Rincón, A. D., Ramezani, J., Solórzano, A., and O. W. M. Rauhut. 2014. New dinosaur (Theropoda, stem-Averostra) from the earliest Jurassic of the La Quinta Formation,
Venezuelan Andes. Royal Society Open Science 1: 140184.
http://dx.doi.org/10.1098/rsos.140184

Abstract - Dinosaur skeletal remains are almost unknown from northern South America. One of the few exceptions comes from a small outcrop in the northernmost extension of the Andes, along the
western border of Venezuela, where strata of the La Quinta Formation have yielded the ornithischian Laquintasaura venezuelae and other dinosaur remains. Here, we report isolated bones (ischium and tibia) of a small new theropod, Tachiraptor admirabilis gen. et sp. nov., which differs from all previously known members of the group by an unique suite of features of its tibial articulations. Comparative/phylogenetic studies place the new form as the sister taxon to Averostra, a theropod group that is known primarily from the Middle Jurassic onwards. A new U–Pb zircon date (isotope dilution thermal-ionization mass spectrometry; ID-TIMS method) from the bone bed matrix suggests an earliest Jurassic maximum age for the La Quinta Formation. A dispersal–vicariance analysis suggests that such a stratigraphic gap is more likely to be filled by new records from north and central Pangaea than from southern areas. Indeed, our data show that the sampled summer-wet equatorial belt, which yielded the new taxon, played a pivotal role in theropod evolution across the Triassic–Jurassic boundary

Tachiraptor admirabilis, a New Theropod Dinosaur from the Earliest Jurassic of Venezuela

     MAURÍLIO OLIVEIRA


The paper will be out on October 8th, but Science's website already has a news article up about the find. It is from the same locality as the early ornithischian dinosaur Laquintasaura, which was described earlier this year.


Lithostratigraphy and biostratigraphy of the Chinle Formation in Lisbon Valley, Utah

The stratigraphy of the Chinle Formation in Lisbon Valley, Utah has been somewhat controversial. This paper is the result of several seasons of fieldwork and provides an intense revision of the local stratigraphy as well as discussion of the fossils found in these rocks. Martz et al. provide a large amount of information and are careful to make sure that their work is repeatable as possible. To this end they provide coordinates and labelled photos of their measured sections as well as a list of voucher specimens for all of the fossil taxa. Martz's work continues to raise the bar not only for studies in the Upper Triassic of Utah, but also for stratigraphic and biostratigraphic work in general.



Martz, J. W., Irmis, R. B., and A.R.C. Milner. 2014. Lithostratigraphy and biostratigraphy of the Chinle Formation (Upper Triassic) in southern Lisbon Valley, southeastern Utah; pp. 397-448 in MacLean, J.S., Biek, R.F., and J.E. Huntoon (eds.), Geology of Utah's Far South. Utah Geological Association Publication 43.

Abstract - We present here a detailed study of the lithostratigraphy and preliminary vertebrate biostratigraphy of the Upper Triassic Chinle Formation in Lisbon Valley, southeastern Utah. Triassic salt tectonism resulted in a period of erosion and possibly non-deposition that removed the top of the Lower Permian Cutler Group, the Early-Middle Triassic Moenkopi Formation, and the Late Triassic (earliest Norian) Shinarump Member of the Chinle Formation. Chinle Formation deposition in Lisbon Valley began or resumed sometime during the middle-late Norian or Rhaetian and terminated before the end of the Rhaetian. Chinle Formation sediments are mostly siltstone to fine-grained sandstone dominated by planar cross-bedding and climbing ripple cross-lamination; these sediments generally exhibit poor paleosol development, with interbedded conglomerates dominated by clasts composed of reworked intrabasinal sediments and containing only minor extrabasinal silica. The regional climate during Chinle deposition was becoming increasingly arid, with fluctuating seasonal rainfall. Deposition by the braided and meandering rivers of the lower Kane Springs beds filled paleovalleys incised into the Cutler Group, and was followed by a poorly drained interval of poorly oxygenated swamps and lakes crisscrossed by small streams that produced the middle Kane Springs beds. These conditions transitioned back to the slowly aggrading braided and meandering rivers of the upper Kane Springs beds, probably by Rhaetian time. The Kane Springs paleoenvironment, probably at least partially syndepositional with that of the Owl Rock Member, was inhabited by conifers, freshwater ostracods, bivalves and gastropods, indeterminate phytosaurs, and the aetosaur Typothorax. The shift to the overlying Church Rock Member was gradational and probably involved only subtle shifts in the depositional system, largely related to better-drained sediments. Braided channels with seasonally variable discharge crossed well-drained, rapidly aggrading and well-oxygenated floodplains. Rare paleosols (including entisols, vertisols, and aridisols) indicate seasonal wetting and drying in a generally arid climate. Rivers and lakes were inhabited by the phytosaur taxon Machaeroprosopus (including the derived form “Redondasaurus”), rare metoposaurids, coelacanths, a diverse actinopterygian fish fauna, conchostracans, ostracods, bivalves, and gastropods. The flora included conifer trees, giant horsetails, Cynepteris (a fern), Zamites (a bennettitalean), the small shrub-like conifer Pelourdea, and the enigmatic Sanmiguelia. Terrestrial tetrapods included the aetosaur Typothorax (suggesting that the genus endured into the Rhaetian), paracrocodylomorphs, and small theropods. Eventually, wind-blown eolian deposits entered the region, and late in the Rhaetian, prior to 201.3 Ma, the eolian Wingate erg swamped small braided channels still inhabited by the phytosaur “Redondasaurus,” actinopterygian fishes, and small theropods.

Triassic Research at the 4th International Paleontology Congress - 2014

Wishing I could have joined my colleagues this week for the 4th International Paleontology Congress in Mendoza, Argentina.  There is a large amount of Triassic research being presented at this meeting.
Here is the link to the abstract volume.





Evidence of Trophic Interactions Among Apex Predators in the Late Triassic

Let's get back into the swing of things Chinle with this new paper that shows how badass phytosaurs were. I'd love to see someone recreate this fight scene for a film.

Drumheller, S. K., Stocker, M. R., and S. J. Nesbitt. 2014. Direct evidence of trophic interactions among apex predators in the Late Triassic of western North America. Naturwissenschaften (advance online publication) DOI: 10.1007/s00114-014-1238-3

 Abstract - Hypotheses of feeding behaviors and community structure are testable with rare direct evidence of trophic interactions in the fossil record (e.g., bite marks). We present evidence of four predation, scavenging, and/or interspecific fighting events involving two large paracrocodylomorphs (='rauisuchians') from the Upper Triassic Chinle Formation (~220–210 Ma). The larger femur preserves a rare history of interactions with multiple actors prior to and after death of this ~8–9-m individual. A large embedded tooth crown and punctures, all of which display reaction tissue formed through healing, record evidence of a failed attack on this individual. The second paracrocodylomorph femur exhibits four unhealed bite marks, indicating the animal either did not survive the attack or was scavenged soon after death. The combination of character states observed (e.g., morphology of the embedded tooth, ‘D’-shaped punctures, evidence of bicarination of the marking teeth, spacing of potentially serial marks) indicates that large phytosaurs were actors in both cases. Our analysis of these specimens demonstrates phytosaurs targeted large paracrocodylomorphs in these Late Triassic ecosystems. Previous distinctions between 'aquatic' and 'terrestrial' Late Triassic trophic structures were overly simplistic and built upon mistaken paleoecological assumptions; we show they were intimately connected at the highest trophic levels. Our data also support that size cannot be the sole factor in determining trophic status. Furthermore, these marks provide an opportunity to start exploring the seemingly unbalanced terrestrial ecosystems from the Late Triassic of North America, in which large carnivores far outnumber herbivores in terms of both abundance and diversity.

Palaeontology Online: Fossil Focus: Placodonts

This link is to a new article at Palaeontology Online providing an overview of Triassic marine placodonts. Palaeontology Online is a website sponsored by the Palaeontological Association (who publish the journal Palaeontology) featuring regular articles written by subject experts on all aspects of paleontology.

Return to the Down's Quarry

The Placerias Quarry outside of St. Johns, Arizona is one of the best known vertebrate fossil localities in the Chinle Formation. The nearby Downs Quarry is not as well known.  Named for the late Will Downs who worked in the area in the 1970s with the Museum of Arizona, the Downs Quarry is just a stones throw from the Placerias Quarry and possibly slightly higher stratigraphically.  Crews from the North Carolina State Museum and Appalachian State University have been working these two sites for five years now and are uncovering a lot of good material.  This is exciting as these quarries have produced a lot of incredible material in the past and seem to still be very productive.  Vince Schneider from the NCSM has a blog posted describing some of the work at the Downs Quarry, which you can read here.

Antarctosuchus polyodon, a new Temnospondyl from the Middle Triassic of Antarctica and Evidence for the Provincialization of the Temnospondyl Assemblages of Gondwana

I've always been interested in the Triassic rocks of Antarctica since as a work-study student at the Museum of Northern Arizona in the 1990s, I was tasked with returning a loan back to the American Museum of Natural History. Turns out it was Edwin Colbert's collection of material from Antarctica.  I was spellbound handling and packing away leaves of Glossopteris and specimens of Thrinaxodon and Dicynodon. These were specimens I had read about when I was younger that helped nail down the theory of plate tectonics, and here I was handling them and packing them for shipment (I hope they made it OK). In graduate school in the late 1990s we were tasked with writing a mock NSF proposal.  Mine dealt with collecting fossils in the Transantarctic Mountains and I'm happy to say it was the only one 'funded' by the professor, but of course I did not really get to go. As a result I'm always envious when  I read about Antarctic work.

This is a paper in the new issue of the Journal of Vertebrate Paleontology describing a new temnospondyl from the Middle Triassic of Antarctica.  This new taxon, Antarctosuchus polyodon, is based on a well preserved skull and a reconstruction is provided below courtesy of Christian Sidor.


This new taxon and its phylogenetic relationships suggests that the Gonwanan temnospondyl faunal assemblages were more provincial than the synapsid assemblages.

Sidor, C. A., Steyer, J. S., and W. R. Hammer. 2014. A new capitosaurid temnospondyl from the Middle Triassic Upper Fremouw Formation of Antarctica. Journal of Vertebrate Paleontology 34(3):539-548. DOI:10.1080/02724634.2013.808205

Abstract - We describe a new capitosauroid temnospondyl, Antarctosuchus polyodon, gen. et sp. nov., on the basis of a large and relatively complete skull from the upper Fremouw Formation of Antarctica. The new species is characterized by its possession of numerous, extremely small maxillary, palatine, and ectopterygoid teeth, a dental pattern that suggests specialization on small prey items, possibly invertebrates. The taxon is also characterized by a parachoanal tooth row that extends far posterior to the choana and occipital condyles set close to the midline. A combination of features, including a flat skull and low occiput together with well-developed sensory canals, suggests an aquatic lifestyle. We address the phylogenetic relationships of Antarctosuchus by adding it to a recent cladistic analysis of Capitosauria. The revised data set includes 27 taxa and 53 characters. The results of this analysis place Antarctosuchus within a clade of derived Triassic stereospondyls as the sister taxon to Paracyclotosaurus crookshanki from the Triassic Denwai Formation of India. To date, the upper Fremouw Formation has yielded two endemic temnospondyl species (viz., Kryostega collinsoni and Antarctosuchus polyodon), although indeterminate remains referred to benthosuchids and a cranial fragment assigned to Parotosuchus sp. have also been noted. In contrast to the broadly distributed therapsid taxa recognized from the Middle Triassic of Antarctica (e.g., Cynognathus, Diademodon), the temnospondyl fauna suggests more limited interchange with other coeval southern Pangean basins (e.g., Karoo, Luangwa, Ruhuhu, Waterberg).


New Article on the Colorado Plateau Coring Project

I apologize for the hiatus since the last set of posts but I was very busy finishing up my scholastic career, as well as maintain my full-time job, and we as my private life with home and family.  I hope to start posting regularly again and possibly even something more than just new paper updates, but we shall see.

This is an article that came out this week on the Colorado Plateau Coring Project work that was completed earlier at Petrified Forest National Park and what we hope to learn from this core.  The core is presently being CT scanned at the UT Austin and after that is will be split and the detailed research started.

https://www.ldeo.columbia.edu/news-events/amid-fossil-bonanza-drilling-deep-pre-dinosaurian-rocks

This summer we will continue work on the layer briefly mentioned in the article and video. An extremely fossiliferous layer we affectionately call the 'poop layer' because it is not only chock full of bones (micro- and macro-) but also a predominance of coprolites.  I'll post updates on our work during the summer.  In the meantime enjoy the article and video.

New Neopterygian Fishes from the Chinle Formation of Utah

This is an important new paper describing some new fishes from the Chinle Formation of Utah. Well-preserved fish are rare throughout much of the Chinle and relatively understudied in previous decades.  Nonetheless, they were important constituents of the Late Triassic biota, and much material goes unrecognized because many Chinle Formation workers (myself included) are one, unfamiliar with the fish fossil record, and two, the taxonomy of this group is in serious need of revision.  Sarah's new work and phylogenentic study is a huge step forward in rectifying these problems. We should all start paying more attention.

Gibson, S. Z. 2013. Biodiversity and Evolutionary History of Lophionotus (Neopterygii: Semionotiformes) from the Western United States. Copeia 2013:582-603. DOI: 10.1643/CI-12-028

Abstract - Two species of the neopterygian genus †Lophionotus Gibson, 2013, are described. Specimens of †Lophionotus chinleana, new species, were previously and recently collected from freshwater deposits in the Upper Triassic Chinle Formation of Lisbon Valley, southeastern Utah. †Semionotus kanabensis Schaeffer and Dunkle, 1950, from lacustrine deposits in the Lower Jurassic Moenave Formation of southwestern Utah, is herein redescribed and attributed to the genus †Lophionotus, based on shared characters, including the infraorbital in the posteroventral corner of the orbit being expanded and contacting the anterior ramus of the preoperculum. Both new species of †Lophionotus are distinct from †L. sanjuanensis Gibson, 2013, in that they lack a postcranial hump, deep body, dense tuberculation, and ventrally expanded preoperculum. The addition of two new species lends to a revised generic description of the genus †Lophionotus. A phylogenetic analysis infers a monophyletic †Lophionotus sister to the genus †Semionotus, and †Lophionotus is placed within the family †Semionotidae within †Semionotiformes.

Ice Archosauromorph


 Recent retreat of ancient ice sheets from western Virginia has revealed the frozen exquisitely preserved remains of a phytosaurian archosaur. The specimen appears to be of the fully crested type, similar to Nicrosaurus kapffi, previously only known from Germany. As the photos below demonstrate, even details of the soft tissue are preserved giving us amazing insight of this animal such as proportions, posture, and that it had bulgy eyeballs. 
 



 A close-up of the pes shows that digit four is the longest, supporting the hypothesis that the ichnoform Apatopus is indeed the track of phytosaurians.


Discoverers Michelle Stocker and Sterling Nesbitt are taking measurements and describing the new find before the Spring thaw, hopefully publishing the results soon.  In the meantime they are also eagerly awaiting what other rare forms may be exposed as these thick deposits of eastern ice finally retreat.

 




Triassic Period: Reptiles Rule. Video from the Discovery Channel.

I assume this is supposed to be the southwest U.S. during the Late Triassic, but there is a hodge-podge of animals from different ages. Still pretty cool though; however, I wish the aetosaur and photosaur were on the scene a little longer, and where is the ubiquitous Postosuchus?

http://www.discovery.com/video-topics/other/dinosaur-videos/triassic-period-reptiles-rule.htm

Large Body Size in Non-dinosaurian Dinosauromorphs - Evidence from a Large Silesaurid from Late Triassic of Tanzania

Barrett, P. M., Nesbitt, S. J., and B. R. Peecook. 2014. A large-bodied silesaurid from the Lifua Member of the Manda beds (Middle Triassic) of Tanzania and its implications for body-size evolution in Dinosauromorpha. Gondwana Research (accepted manuscript). http://dx.doi.org/10.1016/j.gr.2013.12.015

Abstract
- Many dinosaur lineages were characterised by wide ranges of body-size, ranging from taxa that were <1 m in length to the largest of all terrestrial vertebrates. On the other hand, the closest relatives of dinosaurs, the non-dinosaurian dinosauromorphs, such as Marasuchus and lagerpetids, were small-bodied animals with little variation in body-size. Here, we describe a partial femur of an unexpectedly large-bodied silesaurid (non-dinosaurian dinosauriform) from the Lifua Member of the Manda beds (?late Anisian) from southwestern Tanzania. This specimen (NHMUK R16303) is estimated to have had a femoral length of approximately 345 mm, which exceeds that of many Triassic and Lower Jurassic dinosaurs, and is either a large individual of the contemporary Asilisaurus kongwe or represents a new and otherwise unknown silesaurid taxon. In either case, it shows that body-size increases were more prevalent among early dinosauromorphs than realised previously. Moreover, silesaurid size increase occurred in parallel with that in early dinosaurs, alongside the convergent acquisition of other features related to locomotion and herbivory. However, Late Triassic faunas including large-bodied sauropodomorph and theropod dinosaurs lack similarly-sized non-dinosaurian dinosauromorphs, whereas the Lifua Member fauna includes both a large silesaurid and the early ?dinosaur Nyasasaurus, which overlapped in size.

New Open Access Paper Discussing the Rise of Dinosaurs

Benton, M.J., Forth, J., and M.C. Langer. 2014. Models for the rise of dinosaurs. Modern Biology 24:R87-R95. doi:10.1016/j.cub.2013.11.063

Abstract - Dinosaurs arose in the early Triassic in the aftermath of the greatest mass extinction ever and became hugely successful in the Mesozoic. Their initial diversification is a classic example of a large-scale macroevolutionary change. Diversifications at such deep-time scales can now be dissected, modelled and tested. New fossils suggest that dinosaurs originated early in the Middle Triassic, during the recovery of life from the devastating Permo-Triassic mass extinction. Improvements in stratigraphic dating and a new suite of morphometric and comparative evolutionary numerical methods now allow a forensic dissection of one of the greatest turnovers in the history of life. Such studies mark a move from the narrative to the analytical in macroevolutionary research, and they allow us to begin to answer the proposal of George Gaylord Simpson, to explore adaptive radiations using numerical methods.

The Foot of Poposaurus gracilis, Further Convergence with Theropod Dinosaurs

....and the answer to the question we've all been wondering...what type of footprint would Poposaurus have left? It appears that Poposaurus  probably could have left a Grallator-like track.

Farlow, J. O., Schachner, E. R., Sarrazin, J. C., Klein, H., and P. J. Currie. 2014. Pedal Proportions of Poposaurus gracilis: Convergence and Divergence in the Feet of Archosaurs. The Anatomical Record, Early View. DOI: 10.1002/ar.22863.

Abstract - The crocodile-line basal suchian Poposaurus gracilis had body proportions suggesting that it was an erect, bipedal form like many dinosaurs, prompting questions of whether its pedal proportions, and the shape of its footprint, would likewise “mimic” those of bipedal dinosaurs. We addressed these questions through a comparison of phalangeal, digital, and metatarsal proportions of Poposaurus with those of extinct and extant crocodile-line archosaurs, obligate or facultatively bipedal non-avian dinosaurs, and ground birds of several clades, as well as a comparison of the footprint reconstructed from the foot skeleton of Poposaurus with known early Mesozoic archosaurian ichnotaxa. Bivariate and multivariate analyses of phalangeal and digital dimensions showed numerous instances of convergence in pedal morphology among disparate archosaurian clades. Overall, the foot of Poposaurus is indeed more like that of bipedal dinosaurs than other archosaur groups, but is not exactly like the foot of any particular bipedal dinosaur clade. Poposaurus likely had a digitigrade stance, and its footprint shape could have resembled grallatorid ichnotaxa, unless digit I of the foot of Poposaurus commonly left an impression.