A new skeleton of the therocephalian synapsid Olivierosuchus parringtoni from the Lower Triassic South African Karoo Basin

Abstract

We provide a redescription of the therocephalian therapsid Olivierosuchus parringtoni based on a new specimen recovered from the Lower Triassic Lystrosaurus Assemblage Zone of South Africa and discuss the biostratigraphic implications of Lower Triassic South African therocephalians. The new specimen comprises a skull and articulated anterior portion of the postcranial skeleton. Olivierosuchus parringtoni can be distinguished from its akidnognathid relatives, Promoschorhynchus and Moschorhinus, by the presence of a relatively slender snout. Features that further distinguish Olivierosuchus from Promoschorhynchus include fewer upper postcanines, an obtuse angle of the transverse process of the pterygoid and an oblique alignment of the suborbital fenestra margin of the palatine. Features that further distinguish Olivierosuchus from Moschorhinus include the presence of a sharp rather than blunt crista choanalis, a spatulate posterior portion of the ectopterygoid instead of a narrow shaft, the presence of prominent pterygoid tuberosities and a narrow, elongated tabular. A reappraisal of Lower Triassic therocephalian biostratigraphy reveals that most of these taxa are restricted to the lowermost part of the Lystrosaurus Assemblage Zone revealing a high diversity, whereafter the diversity decreases dramatically in the middle of the zone. However, despite their scarcity in the middle and upper Lystrosaurus Assemblage Zone, therocephalians in the Karoo Basin remain the most diverse therapsid clade in the lowermost Triassic, which suggests that they were able to recover relatively quickly from the endPermian extinction event and form an important part of the postextinction earliest Triassic recovery.

Vertebrate Paleontology of Nooitgedacht 68: A Lystrosaurus maccaigi-Rich Permo-Triassic Boundary Locality in South Africa

“…Our latest field expedition also produced a Proterosuchus fergusi skull from the Lower Triassic Palingkloof Member of the Lystrosaurus Assemblage Zone from Spitskop. Both Olivierosuchus and Proterosuchus are restricted to the lowermost Triassic Lystrosaurus Assemblage Zone, and along with the presence of Triassic Lystrosaurus species, confirm an Early Triassic age for the uppermost slopes of Loskop and Spitskop (Botha and Smith 2006;Botha-Brink and Modesto 2011).…”

A new therocephalian (Gorynychus masyutinae gen. et sp. nov.) from the Permian Kotelnich locality, Kirov Region, Russia

“…Before such data can be incorporated into therocephalian analyses, however, more basic descriptive work on therocephalian postcrania is needed. Although skeletons are now known for a wide array of taxa, anatomical descriptions are currently available for only a select few ( Kemp, 1986 ; Fourie & Rubidge, 2009 ; Botha-Brink & Modesto, 2011 ; Fourie, 2013 ).…”

The tetrapod fauna of the upper Permian Naobaogou Formation of China: 5. Caodeyao liuyufengi gen. et sp. nov., a new peculiar therocephalian

“…A robust, vertical anterior symphyseal region is known in several therocephalian groups including basal therocephalians such as Gorynychus, Lycosuchus, and some scylacosaurids (Abdala et al, 2014b;Abdala, Rubidge & Van den Heever, 2008;Kammerer & Masyutin, 2018;Pusch et al, 2020). This condition is also present in some eutherocephalians, including akidnognathids such as Moschorhinus, Olivierosuchus, and Promoschorhynchus (''mental protuberance'') (Botha- Brink & Modesto, 2011;Durand, 1991;Huttenlocker, Sidor & Smith, 2011) and bauriamorphs such as Nothogomphodon (Ivakhnenko, 2011;Liu & Abdala, 2015), and Microgomphodon (Abdala et al, 2014a). Development of a tall mandibular symphysis is extreme in the Russian Purlovia, in which there is a marked ventral chin (Ivakhnenko, 2011: Fig.…”