Field of Science

Reanalysis of the Diapsid Reptile Elachistosuchus huenei from the Late Triassic of Germany

Sobral, G., Sues, H.-D., and J. Müller. 2015. Anatomy of the enigmatic reptile Elachistosuchus huenei Janensch, 1949 (Reptilia: Diapsida) from the Upper Triassic of Germany and its relevance for the origin of Sauria. PLoS ONE 10(9): e0135114. doi:10.1371/journal.pone.0135114

Abstract - The holotype and only known specimen of the enigmatic small reptile Elachistosuchus huenei Janensch, 1949 from the Upper Triassic (Norian) Arnstadt Formation of Saxony-Anhalt (Germany) is redescribed using μCT scans of the material. This re-examination revealed new information on the morphology of this taxon, including previously unknown parts of the skeleton such as the palate, braincase, and shoulder girdle. Elachistosuchus is diagnosed especially by the presence of the posterolateral process of the frontal, the extension of the maxillary tooth row to the posterior margin of the orbit, the free posterior process of the jugal, and the notched anterior margin of the interclavicle. Phylogenetic analyses using two recently published character-taxon matrices recovered conflicting results for the phylogenetic position of Elachistosuchus–either as an archosauromorph, as a lepidosauromorph or as a more basal, non-saurian diapsid. These different placements highlight the need of a thorough revision of critical taxa and new character sets used for inferring neodiapsid relationships.

The Dicynodon-Lystrosaurus Assemblage Zone Boundary May Not Approximate the Marine-Defined Permo-Triassic Extinction Event

Wow, well this should definitely generate some discussion and a bit of research.... 

Gastaldo, R. A., Kamo, S. L., Neveling, J., Geissman, J. W., Bamford, M., and C. V. Looy. 2015 Is the vertebrate-defined Permian-Triassic boundary in the Karoo Basin, South Africa, the terrestrial expression of the end-Permian marine event? Geology (Advanced Online). doi: 10.1130/G37040.1

Abstract: The end-Permian extinction records the greatest ecological catastrophe in Earth history. The vertebrate fossil record in the Karoo Basin, South Africa, has been used for more than a century as the standard for understanding turnover in terrestrial ecosystems, recently claimed to be in synchrony with the marine crisis. Workers assumed that systematic turnover at the Dicynodon assemblage zone boundary, followed by the appearance of new taxa directly above the base of the Lystrosaurus assemblage zone, is the continental expression of the end-Permian event and recovery. To test this hypothesis, we present the first highprecision age on strata close to the inferred Permian-Triassic boundary. A U-Pb isotope dilution–thermal ionization mass spectrometry zircon age of 253.48 ± 0.15 Ma (early Changhsingian) is from a silicified ash layer ~60 m below the current vertebrate-defined boundary at Old Lootsberg Pass (southern South Africa). This section yields newly discovered plants and vertebrates, and is dominated by a normal polarity signature. Our collective data suggest that the Dicynodon-Lystrosaurus assemblage zone boundary is stratigraphically higher than currently reported, and older than the marine extinction event. Therefore, the turnover in vertebrate taxa at this biozone boundary probably does not represent the biological expression of the terrestrial end-Permian mass extinction. The actual Permian-Triassic boundary in the Karoo Basin is either higher in the Katberg Formation or is not preserved. The currently accepted model of the terrestrial ecosystem response to the crisis, both in this basin and its extension globally, requires reevaluation.

So Long Paleorhinus and Pseudopalatinae

Long needed redescription of the type material of the phytosaur Parasuchus hislopi from India and a revision of the non-mystriosuchin parasuchid phytosaurs. It will take me awhile to abandon the name Pseudopalatinae. 

Kammerer, C. F., Butler, R. J., Bandyopadhyay, S., and M. R. Stocker. 2015. Relationships of the Indian phytosaur Parasuchus hislopi Lydekker, 1885. Papers in Paleontology (early online). 

The neotype skull of the Indian phytosaur Parasuchus hislopi Lydekker, 1885 (ISI R42) is re-evaluated and compared with the type material of other basal phytosaurs. Parasuchus hislopi is extremely similar to species previously placed in Paleorhinus (P. bransoni and P. angustifrons), sharing with them such characters as a series of nodes on the lateral surface of the jugal, paired ridges on the squamosal and a frontal depression. Parasuchus hislopi represents a valid species: it can be distinguished from P. bransoni by a relatively low narial eminence and P. angustifrons by the absence of paired nasal depressions. Inclusion of Parasuchus hislopi in a phylogenetic analysis of phytosaurs recovers it in a well-supported clade with P. bransoni and P. angustifrons. Parasuchus is considered the senior synonym of Paleorhinus and Arganarhinus. Parasuchus (here considered to include P. hislopi, P. angustifrons, P. bransoni and P. magnoculus) has a broad circum-Pangaean distribution, with species occurring in the south-western United States, Morocco, central Europe and India. Phytosaur higher-level taxonomy is also revised: Parasuchidae is redefined to include ‘Paleorhinus-grade’ phytosaurs and the later-diverging Mystriosuchinae (the group formerly known as Phytosauridae), and Pseudopalatinae is renamed Mystriosuchini for reason of priority.

A New Lagerpetid Dinosauromorph from the Late Triassic of Argentina

Martínez, R. N., Apaldetti, C., Correa, G. A., and D. Abelín. 2015. A Norian lagerpetid dinosauromorph from the Quebrada del Barro Formation, northwestern Argentina. Ameghiniana (future issue) doi:10.5710/AMGH.21.06.2015.2894

The early evolution of Ornithodira, the clade that includes pterosaurs and dinosaurs, is poorly known. Until a decade ago, the basal radiation of Dinosauromorpha, the clade including dinosaurs and birds, was poorly understood because of a scarce of fossil record, which was restricted to specimens known of the Ladinian Chañares Formation from Argentina. In the last years the discovery of several non-dinosaurian dinosauromorphs dramatically expanded this record and also demonstrated that this group—previously restricted to the Middle Triassic—persisted at least well into the Norian. Although Norian non-dinosaurian dinosauromorphs have been reported from several places around the world, the only known Norian non-dinosauriform dinosauromorphs—Dromomeron romeri and Dromomeron gregorii—come from North America. We report here the first record from the Southern Hemisphere of a non-dinosauriform dinosauromorph, Dromomeron gigas sp. nov., from the Norian Quebrada del Barro Formation, northwestern Argentina. A phylogenetic analysis recovers Dromomeron gigas nested into the monophyletic group Lagerpetidae, and as the sister taxon to Dromomeron romeri. The inclusion of D. gigas within Lagerpetidae suggests that body size increased in this lineage over time, as was previously demonstrated for Dinosauriformes as a whole, and that lagerpetids reached a larger size than previously thought. Finally, the new finding provides novel information on the basal radiation of Dinosauromorpha constituting the first record of a Norian association of dinosaurs with non-dinosauriform dinosauromorphs outside North America.

Evidence of Interaction between Two Late Triassic Apex Predators

I've been away for a bit, but am interested in trying to get back into the swing of things here so please bear with me.  This is a paper from late last year that I haven't mentioned before.

Drumheller, S. K., M. R. Stocker, and S. J. Nesbitt. 2014. Direct evidence of trophic interactions among apex predators in the Late Triassic of western North America. Naturwissenschaften 101:975-987. DOI 10.1007/s00114-014-1238-3

Rather than get into the details here I'll send you to this podcast which does a great job featuring the significance of this study.

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:

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


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.