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[dinosaur] Euchambersia as venomous therocephalian + Predator-prey interactions among Permo-Triassic land vertebrates + South American cynodonts

Ben Creisler

Some new and not so recent non-dino papers:

Julien Benoit (2016)
A review of the “venomous therocephalian” hypothesis and how multiple re-portrayals of Euchambersia have influenced its success and vice versa.
Bulletin de la Société Géologique de France 187 (4-5): 217-224

Euchambersia mirabilis is unique amongst Permo-Triassic therapsids because it has an external maxillary fossa associated with a ridged canine. This anatomy led to the commonly accepted conclusion that the fossa accommodated a venom gland, which would make Euchambersia the earliest known venomous land vertebrate. Indeed, Euchambersia is considered to be the most robustly supported case of an extinct venomous species and serves as a model for infering envenoming capacity in fossil species. Here, a review of the literature on Euchambersia, with special emphasis on canine morphology, shows that this hypothesis is often based on inaccurate drawings of the canine and, for post-1986 authors, it is even based on the assumption that the canine of Euchambersia is grooved, whereas it is actually only ridged. This does not invalidate the venomous therocephalian hypothesis, but nevertheless emphasizes the critical importance of first hand observations of original material for any type of work in vertebrate paleontology. This review offers an interesting example of how observations and the resulting scientific hypotheses interact, grow, and can reciprocally influence each other.


Jacqueline Codron, Jennifer Botha-Brink, Daryl Codron, Adam K Huttenlocker & Kenneth D Angielczyk (2016)
Predator-prey interactions among Permo-Triassic terrestrial vertebrates as a deterministic factor influencing faunal collapse and turnover.
Journal of Evolutionary Biology (advance online publication)
DOI: 10.1111/jeb.12983

Unlike modern mammalian communities, terrestrial Paleozoic and Mesozoic vertebrate systems were characterized by carnivore faunas that were as diverse as their herbivore faunas. The comparatively narrow food base available to carnivores in these paleosystems raises the possibility that predator-prey interactions contributed to unstable ecosystems by driving populations to extinction. Here we develop a model of predator-prey interactions based on diversity, abundance, and body size patterns observed in the Permo-Triassic vertebrate fossil record of the Karoo Basin, South Africa. Our simulations reflect empirical evidence that despite relatively high carnivore:herbivore species ratios, herbivore abundances were sufficient for carnivores to maintain required intake levels through most of the Karoo sequence. However, high mortality rates amongst herbivore populations, even accounting for birth rates of different-sized species, are predicted for assemblages immediately preceding the end-Guadalupian and end-Permian mass extinctions, as well as in the Middle Triassic when archosaurs replaced therapsids as the dominant terrestrial fauna. These results suggest that high rates of herbivore mortality could have played an important role in biodiversity declines leading up to each of these turnover events. Such declines would have made the systems especially vulnerable to subsequent stochastic events and environmental perturbations, culminating in large-scale extinctions.


Also, a paper from a recent publication available in Research Gate:

Agustín G. Martinelli & Marina Bento Soares (2016)
Evolution of South American non-mammaliaform cynodonts (Therapsida, Cynodontia).
Historia Evolutiva y Paleobiogeografía de los Vertebrados de América del Sur. Contribuciones del MACN (Editors: F. Agnolíin, G.L. Lio, F. Brissón Egli, N.R. Chimento, F. Novas) 6: 183-197

Cynodonts constitute a conspicuous group of synapsids within Triassic continental faunal assemblages. The fossil record of cynognathians (including traversodontids) and nonmammaliaform probainognathians is remarkable in South America, especially in western Argentina and southern Brazil, representing the cornerstone to understand Middle to Late Triassic cynodont evolution. In this contribution we present an overview of South American non-mammaliaform cynodonts and some taxonomic and biostratigraphic comments.