New Record of Large Archosauromorphs from the Early Triassic of Antarctica

Smith, N. D., Crandall, J. R., Hellert, S. M., Hammer, W. R., and P. J. Makovicky. 2011. Anatomy and affinities of large archosauromorphs from the lower Fremouw Formation (Early Triassic) of Antarctica. Journal of Vertebrate Paleontology 31:784-797. DOI:10.1080/02724634.2011.586662

Abstract - The vertebrate assemblage of the lower Fremouw Formation has been studied for nearly 50 years, but many components remain poorly known. We describe a partial presacral vertebra and the distal end of a left humerus collected just above the Permian–Triassic boundary in the Shackleton Glacier region of the central Transantarctic Mountains. Our identification of these specimens as archosauromorphs that represent at least one taxon of large-bodied archosauriform increases the known reptile diversity of the Fremouw Formation considerably, and provides the first definitive evidence for the presence of Archosauriformes in the Early Triassic of Antarctica. These records increase faunal similarities between the lower Fremouw Formation and other Early Triassic assemblages. Although the lower Fremouw assemblage is typically considered a subset of the coeval Lystrosaurus Assemblage Zone (LAZ) of South Africa, the discrepancy in inferred body size between the Antarctic specimens and Proterosuchus fergusi, coupled with the fact that the LAZ of the Karoo Basin has been sampled much more thoroughly, suggests a real disparity in the maximum body size of apex carnivores between the lower Fremouw assemblage and the LAZ. The lower Fremouw specimens also demonstrate that one or more lineages of archosauriform had attained the large body size characteristic of later members of the clade very soon after the end-Permian mass extinction. This offers a point of contrast with the global pattern of post-extinction terrestrial communities, which are typified by a marked reduction in body size (the ‘Lilliput effect’).

Two New Cynodont Papers from the Middle Triassic of Gondwana

The first paper is a short note so there is no abstract.


Kammerer, C. F., Flynn, J. J., Ranivoharimanana, L. and A. R. Wyss. 2010. The first record of a probainognathian (Cynodontia: Chiniquodontidae) from the Triassic of Madagascar. Journal of Vertebrate Paleontology 30:1889-1894. DOI: 10.1080/02724634.2010.520784

Note: The authors state that this specimen is probably Middle Triassic in age, but could possibly be as young as Carnian.


Martinelli, A. G. 2010. On the postcanine dentition of Pascualgnathus polanskii Bonaparte (Cynodontia, Traversodontidae) from the Middle Triassic of Argentina. Geobios 43:629–638


Abstract - The dental morphology of Pascualgnathus polanskii Bonaparte (Therapsida, Eucynodontia, Traversodontidae), from the Middle Triassic Río Seco de la Quebrada Formation (Puesto Viejo Group, Argentina), is described and compared with that of other basal traversodontid cynodonts. Albeit Pascualgnathus is frequently used in phylogenetic analyses, neither a detailed description nor drawings of its postcanines have been published so far. The upper postcanines of Pascualgnathus are transversely wide, rectangular in occlusal view, with a lingual cusp connected to the transverse ridge which is located in the center of the crown, and one main labial cusp followed by one posterior labial, both forming the labial margin. The lower postcanines, mostly worn out in the known specimens, are quadrangular until pc6 and then they are rectangular with the major axis anteroposteriorly oriented. They have a tall mesial border, possibly constituted by one labial and one lingual cusp, and a transverse ridge. After comparisons, the number of cusps in the sectorial, labial border of the upper gomphodont teeth, frequently used in phylogenetic analyses, would not necessary implies real homologies. For example, postcanine morphologies with one or more cusps anterior to the main labial cusp would not be homologous to morphologies with one or more cusps posterior to the main labial cusp, while resulting in a similar count of labial cusps.

Stratigraphic Correlations of Gondwanan Basins in India and the "Laurasian" Fauna of Northern Gondwana in the Late Triassic

Here is a fairly obscure, but interesting new paper providing updated correlations of strata (including that of Triassic age) in the Gondwanan Basins of India. The final paper could have benefited from some more editing, but overall it provides a decent synthesis and outlines some of the problems of correlations in this are of Gondwana. Most significant is that there are no absolute time constraints available for these strata because of the lack of datable volcanic materials. The overall climate for the entire Triassic for this area is given as arid with a key sea level regression in the Norian. Note, however, that the authors explicitly use the 2004 ISC timescale, and that under currently proposed revisions to this timescale the Carnian is more restricted.

The Triassic vertebrate fauna of India has always struck me as bizarre, mainly because the Early Triassic fauna is extremely similar to that of the Lystrosaurus assemblage zone of South Africa, and does contain several species of Lystrosaurus. Yet the Middle and Late Triassic fauna has much more of a Laurasian feel to it, especially the Late Triassic fauna, which includes basal phytosaurs such as Parasuchus, and more advanced phytosaurs such as a Leptosuchus-like form. Aetosaurs are represented by a paratypothoracisine form, which are only known from North America and Europe. Finally, metoposaurid temnospondyls are also common as in North America and Europe.

This seems very odd to me given that in paleogeographic reconstructions throughout the Triassic, India is firmly nestled on the western edge of modern day Africa, contacting Australia, and Antarctica, and separated from North America by all of northern Africa and from Europe by the Tethys. Unfortunately the Triassic fauna of North Africa is extremely sparse, although the Moroccan fauna is very similar to that of India and Laurasia. Perhaps Northern Africa served as a corridor for the Laurasian-type fauna, whereas there was some restriction from South America and South Africa in the Latest Triassic.  Thus it seems that at this time there are not distinct Laurasian and Gondwanan distributions of tetrapods, but rather separate southern Gondwana and northern Gondwana/Laurasia distributions.

Mukhopadhyay, G., Mukhopadhyay, S. K., Roychowdhury, M., and P. K. Parui. 2010. Stratigraphic Correlation between Different Gondwana Basins of India.
Journal of the Geological Society of India 76:251-266. DOI: 10.1007/s12594-010-0097-6

Abstract - Gondwana Basins of India occur within the suture zones of Precambrian cratonic blocks of Peninsular India along some linear belts. More than 99% of the total coal resource of the country is present within these basins. The basins are demarcated by boundary faults having graben or half-graben geometry. These basins preserve a thick sedimentary pile deposited over nearly 200 million years from latest Carboniferous to Lower Cretaceous. However, due to lack of well-constrained data, age of most of the formations is assigned tentatively. This has resulted in diversified views on both intra- and inter-basinal stratigraphic correlation particularly in case of Upper Gondwana formations. It is well recognised that there are distinct spatial and temporal similarities in lithological, faunal and floral distribution in different Gondwana Basins of southern continents, including India, that were once part of supercontinent Gondwanaland. To address the problems of Indian Gondwana stratigraphy, during the present study, some unique events, also recognised in other parts of Gondwanaland, like marine flooding surfaces, large scale tectonic events or major change in depositional environment have been used as a tool for temporal correlation within the Gondwana Basins of India. Many of these events have been dated from different basins elsewhere. Considering these major events as time planes the total time span of deposition in Gondwana Basins has been classified into seven time slots. Recognition of these time planes helps in interbasinal correlation of different formations in Indian Gondwana basins and assigning the age, wherever available. This approach also helps in better understanding of basinal history. Unless otherwise mentioned, the time scale proposed by International Commission on Stratigraphy (2004) has been followed in this paper.