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A NEW SKELETON of the THEROCEPHALIAN SYNAPSID OLIVIEROSUCHUS PARRINGTONI from the LOWER TRIASSIC SOUTH AFRICAN KAROO BASIN by JENNIFER BOTHA-BRINK* and SEAN P

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A NEW SKELETON of the THEROCEPHALIAN SYNAPSID OLIVIEROSUCHUS PARRINGTONI from the LOWER TRIASSIC SOUTH AFRICAN KAROO BASIN by JENNIFER BOTHA-BRINK* and SEAN P [Palaeontology, Vol. 54, Part 3, 2011, pp. 591–606] A NEW SKELETON OF THE THEROCEPHALIAN SYNAPSID OLIVIEROSUCHUS PARRINGTONI FROM THE LOWER TRIASSIC SOUTH AFRICAN KAROO BASIN by JENNIFER BOTHA-BRINK* and SEAN P. MODESTOà *Karoo Palaeontology, National Museum, PO Box 266, Bloemfontein 9300, South Africa Department of Zoology and Entomology, University of the Free State, Bloemfontein 9300, South Africa; e-mail: [email protected] àDepartment of Biology, Cape Breton University, Sydney, NS B1P 6L2, Canada; e-mail: [email protected] Typescript received 10 June 2009; accepted in revised form 6 July 2010 Abstract: We provide a redescription of the therocephalian topterygoid instead of a narrow shaft, the presence of promi- therapsid Olivierosuchus parringtoni based on a new specimen nent pterygoid tuberosities and a narrow, elongated tabular. recovered from the Lower Triassic Lystrosaurus Assemblage A reappraisal of Lower Triassic therocephalian biostratigra- Zone of South Africa and discuss the biostratigraphic impli- phy reveals that most of these taxa are restricted to the lower- cations of Lower Triassic South African therocephalians. The most part of the Lystrosaurus Assemblage Zone revealing a new specimen comprises a skull and articulated anterior por- high diversity, whereafter the diversity decreases dramatically tion of the postcranial skeleton. Olivierosuchus parringtoni in the middle of the zone. However, despite their scarcity in can be distinguished from its akidnognathid relatives, Promo- the middle and upper Lystrosaurus Assemblage Zone, thero- schorhynchus and Moschorhinus, by the presence of a relatively cephalians in the Karoo Basin remain the most diverse the- slender snout. Features that further distinguish Olivierosuchus rapsid clade in the lowermost Triassic, which suggests that from Promoschorhynchus include fewer upper postcanines, an they were able to recover relatively quickly from the end- obtuse angle of the transverse process of the pterygoid and an Permian extinction event and form an important part of the oblique alignment of the suborbital fenestra margin of the postextinction earliest Triassic recovery. palatine. Features that further distinguish Olivierosuchus from Moschorhinus include the presence of a sharp rather than Key words: therocephalians, Early Triassic, Lystrosaurus blunt crista choanalis, a spatulate posterior portion of the ec- Assemblage Zone, Karoo Basin, South Africa. T herocephalia constitutes a group of eutheri- falling within the Lystrosaurus Assemblage Zone) include odont therapsids that appeared during the Middle Moschorhinus kitchingi, Ericiolacerta parva, Regisaurus Permian and went extinct during the Middle Triassic jacobi, Zorillodontops gracilis, Olivierosuchus parringtoni (Abdala et al. 2008). Fossils of this group have been (formerly ‘Olivieria’ parringtoni: Kammerer and Sidor recovered from Africa, Eurasia and Antarctica (Hopson 2002) and indeterminate scaloposaurs (Kammerer 2008). and Barghusen 1986; Rubidge and Sidor 2001), but are These taxa form part of the Early Triassic recovery after most abundant in the Karoo Basin of South Africa. the end-Permian extinction event. Moschorhinus kitchingi They are regarded traditionally as the sister group of is restricted to the Palingkloof Member of the Balfour cynodonts (the most derived therapsid group that Formation. Regisaurus jacobi is represented by two speci- includes mammals as their extant subclade), but inde- mens, and Z. gracilis and E. parva are represented by pendently acquired several mammal-like features. single specimens in South Africa, but their exact strati- Therocephalians are also one of the few therapsid graphic levels are unknown (the specimen originally iden- groups to have survived the end-Permian extinction tified as E. parva from the farm Barendskraal, Palingkloof event, with Moschorhinus kitchingi (probably a junior Member, Balfour Formation is probably not assignable to synonym of Tigrisuchus simus according to Mendrez this taxon; SPM, pers. obs.). Only the indeterminate sca- 1974; Kammerer 2008), crossing the Permian ⁄ Triassic loposaurs (previously identified as Ictidosuchoides, Ictido- boundary (Botha and Smith 2006). suchops and Tetracynodon darti, but now thought to be In the South African Karoo Basin (Text-fig. 1), the juvenile baurioids; Kammerer 2008) and O. parringtoni therocephalians present in Lower Triassic strata (and (according to Neveling 2004) have been recovered from ª The Palaeontological Association doi: 10.1111/j.1475-4983.2011.01048.x 591 592 PALAEONTOLOGY, VOLUME 54 A tion, Wellwood, Graaff-Reinet, Eastern Cape Province; SAM, Iziko South African Museum, Cape Town. Anatomical abbreviations. a, angular; a p, atlantal pleurocentrum; a na, atlantal neural arch; at, atlas; ax, axis; ax ns, axial neural spine; bo, basioccipital; c, centrale; cl, clavicle; c r, cervical rib; d, dentary; d1–5, distal carpals; d ph, distal phalanx; ect, ectopteryg- oid; ept, epipterygoid; f, frontal; h, humerus; ic, interclavicle; j, jugal; l, lacrimal; m, maxilla; mc, metacoracoid; n, nasal; p, parie- tal; pal, palatine; pa, proatlas; par, paroccipital process of opis- thotic; pb, parabasisphenoid; pc, procoracoid; pi, pisiform; pm, premaxilla; po, postorbital; postz, postzygapophysis; pp, postpar- ietal; p ph, proximal phalanx; pra, prearticular; prez, prezygapoph- ysis; prf, prefrontal; pro, prootic; pt, pterygoid; qj, quadratojugal; qp pt, quadrate process of pterygoid; r, rib; ra, radius; rd, radiale; rf, reflected lamina of angular; s, stapes; sa, surangular; sc, scapula; so, supraoccipital; sq, squamosal; st, sternum; t, tabular; tp at, transverse process of atlas; tp ax, transverse process of axis; tp pt, B transverse process of pterygoid; t ph, terminal phalanx; u, ulna; ul, ulnare; v, vomer; I–V, metacarpals. MATERIAL AND METHODS The new specimen of Olivierosuchus parringtoni described here was accessioned into the collections of the National Museum as NMQR 3605. It was prepared mechanically using a pneumatic airscribe by J. Nyaphuli (NM), then photographed and illustrated. We used the following taxa and specimens for comparative purposes: Moschorhinus TEXT-FIG. 1. A, Map of South Africa, showing the limit of kitchingi, NMQR 76, NMQR 3568; Promoschorhynchus the Karoo Basin and location of the Permian ⁄ Triassic boundary platyrhinus, RC 116. and B, summary of the litho- and biostratigraphy for the southern and central Karoo Basin indicating the strata noted in this study. Star indicates location of specimen NMQR 3605. The SYSTEMATIC PALAEONTOLOGY Swartberg member is an informal member and not yet approved by the South African Committee for Stratigraphy. Dates taken SYNAPSIDA Osborn, 1903 from Catuneanu et al. (2005). BGDP, Burgersdorp; C.T., Cape THEROCEPHALIA Broom, 1903 Town; D, Durban; FM, Formation; JHB, Johannesburg; KBG, AKIDNOGNATHIDAE Nopcsa, 1923 Katberg; PTB, Permian ⁄ Triassic boundary. OLIVIEROSUCHUS Kammerer and Sidor, 2002 throughout the Lystrosaurus Assemblage Zone and thus were a persistent part of the Early Triassic recovery fauna Type species. Olivierosuchus (= Olivieria) parringtoni (Brink, in South Africa. 1965). A new specimen of O. parringtoni, which includes the anterior portion of the postcranial skeleton, was recently Revised diagnosis. Distinguished from Promoschorhynchus recovered from the Triassic strata of the Palingkloof and Moschorhinus by a relatively narrow snout. Differs Member, Balfour Formation in the southern Karoo Basin. from Promoschorhynchus in having three upper postcanines The new specimen is the largest known specimen of (vs. five or six), transverse flange of pterygoid almost per- O. parringtoni and brings the total number of specimens pendicular to midline (vs. 50 degrees from the midline), assignable to this species to four. We describe the new suborbital fenestra margin of palatine obliquely aligned specimen here and consider the biostratigraphic implica- (vs. transversely aligned). Differs from Moschorhinus in tions of Early Triassic South African therocephalians. that the crista choanalis is sharp (vs. blunt), the posterior portion of the ectopterygoid is spatulate (vs. narrow shaft), Institutional abbreviations. CGP, Council for Geoscience, Preto- pterygoid tuberosities prominent (vs. low ridge), tabular ria; NM, National Museum, Bloemfontein; RC, Rubidge Collec- narrow and elongated (vs. short and broad). BOTHA-BRINK AND MODESTO: NEW SKELETON OF THE THEROCEPHALIAN OLIVIEROSUCHUS 593 Olivierosuchus parringtoni (Brink, 1965) tooth tip. On the right side of the skull, two small maxillary Text-figures 2–5 teeth lie anterior to the tooth tip, suggesting that two preca- nines are present. Akidnognathids are thought to have a Holotype. BP ⁄ 1 ⁄ 3849 (formerly BPI M379), complete skull and reduced number of precanines (from two to one, Hopson and anterior half of skeleton in articulation, including vertebrae, ribs, Barghusen 1986), and thus, it is more likely that the second pectoral girdle, partial left humerus, complete right forelimb, maxillary tooth in the holotype is instead a replacement tooth including terminal phalanges. for the first precanine. There are three postcanines posterior to the large canine Type locality and horizon. Palingkloof Member, Balfour Forma- (there are four postcanines on the left maxilla of NMQR 62, but tion, Beaufort Group. Lystrosaurus Assemblage Zone, Lower the third tooth is significantly smaller than the others and Triassic; locality New Castle of the Admiralty Estates, Bergville appears to be a replacement tooth for
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