bs_bs_banner Zoological Journal of the Linnean Society, 2015, 174, 571–588. With 6 figures Downloaded from https://academic.oup.com/zoolinnean/article-abstract/174/3/571/2453122 by Universidade Estadual Paulista J�lio de Mesquita Filho user on 06 May 2019 A new species of basal rhynchosaur (Diapsida: Archosauromorpha) from the early Middle Triassic of South Africa, and the early evolution of Rhynchosauria RICHARD J. BUTLER1,2*, MARTÍN D. EZCURRA1,2, FELIPE C. MONTEFELTRO1,3, ADUN SAMATHI2,4 and GABRIELA SOBRAL5 1School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK 2GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, 80333 Munich, Germany 3Departamento de Biologia e Zootecnia, UNESP, Rua Monção 226, 15385-000, Ilha Solteira, Brazil 4Division of Paleontology, Steinmann Institute, University of Bonn, Nussallee 8, 53115, Bonn, Germany 5Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115 Berlin, Germany Received 14 August 2014; revised 8 January 2015; accepted for publication 14 January 2015 Rhynchosauria was an important clade of herbivorous archosauromorph reptiles during the Triassic, with a world- wide distribution. We describe a new genus and species of early rhynchosaur, Eohyosaurus wolvaardti gen. et sp. nov., from the early Middle Triassic (early Anisian) Cynognathus Assemblage Zone (Subzone B) of the Karoo Supergroup, South Africa. Eohyosaurus wolvaardti is known from a single skull, and is recovered as the sister taxon of Rhynchosauridae in a new phylogenetic analysis. Cynognathus Subzone B has previously yielded the stratigraphically oldest well-understood rhynchosaur species, Mesosuchus browni and Howesia browni. Eohyosaurus wolvaardti increases the rhynchosaur diversity within this stratigraphical horizon to three species. Intriguingly, all currently confirmed rhynchosaur occurrences from the Early Triassic to earliest Middle Triassic are from South Africa. This may suggest a relatively restricted palaeogeographical distribution for early rhynchosaurs, followed by a global dispersal of rhynchosaurids during the Middle Triassic. © 2015 The Linnean Society of London, Zoological Journal of the Linnean Society, 2015, 174, 571–588. doi: 10.1111/zoj.12246 ADDITIONAL KEYWORDS: Anisian – Burgersdorp Formation – Cynognathus assemblage zone – phylog- eny – Rhynchosauridae. INTRODUCTION 1990; Dilkes, 1995, 1998; Langer et al., 2000; Nesbitt & Whatley, 2004; Montefeltro, Langer & Schultz, 2010; Rhynchosaurs were an important group of herbivo- Ezcurra et al., 2014; Montefeltro et al., 2013; Mukherjee rous archosauromorph reptiles that played a key role & Ray, 2014). The youngest stratigraphical occur- in many terrestrial ecosystems during the Triassic, par- rences of rhynchosaurs occur close to the Carnian– ticularly in Gondwana. The clade diversified during Norian boundary (Langer et al., 2007; Martínez et al., the Middle Triassic and early Late Triassic, with abun- 2011), and the clade has been considered as a victim dant remains known from Tanzania, South Africa, of the possible Carnian–Norian extinction event (Benton, Madagascar, India, Brazil, Argentina, the UK, and the 1983b, 1990). Most rhynchosaurs (i.e. those belong- USA (Huene, 1938; Chatterjee, 1980; Benton, 1983a, ing to the clade Rhynchosauridae) were squat, pig- like herbivores, with unusual skulls characterized by *Corresponding author. E-mail: [email protected] bony beaks and complex tooth plates. © 2015 The Linnean Society of London, Zoological Journal of the Linnean Society, 2015, 174, 571–588 571 572 R. J. BUTLER ET AL. The earliest rhynchosaur, Noteosuchus colletti,is METHODS Downloaded from https://academic.oup.com/zoolinnean/article-abstract/174/3/571/2453122 by Universidade Estadual Paulista J�lio de Mesquita Filho user on 06 May 2019 known from the Lower Triassic Lystrosaurus Assem- INSTITUTIONAL ABBREVIATIONS blage Zone of South Africa (Carroll, 1976; Dilkes, 1998; BRSUG, University of Bristol, School of Earth Sci- Ezcurra, Scheyer & Butler, 2014), shortly after the ences, Bristol, UK; FZB, Fundação Zoobotânica do Rio Permo-Triassic mass extinction. Two basal rhynchosaurs, Grande do Sul, Porto Alegre, Brazil; MACN-Pv, Museo Howesia browni and Mesosuchus browni, are known Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, from the middle part (Subzone B) of the overlying Paleontología de Vertebrados, Buenos Aires, Argenti- Cynognathus Assemblage Zone (AZ; Dilkes, 1995, 1998), na; PVSJ, Museo de Ciencias Naturales, Universidad of early Middle Triassic (early Anisian) age. These taxa de San Juan, San Juan, Argentina; NHMUK, Natural are considered key for understanding the origin and History Museum, London, UK; SAM, Iziko South African early evolution of rhynchosaurs, as many aspects Museum, Cape Town, South Africa; SHYMS, Shrop- of their anatomy are intermediate between other shire Museums, Ludlow, UK; UFRGS, Instituto de early archosauromorphs and more derived rhynchosaurs Geociências, Universidade Federal do Rio Grande do (Rhynchosauridae). Mesosuchus browni, the Sul, Porto Alegre, Brazil; WARMS, Warwickshire stratigraphically oldest well-understood rhynchosaur, Museum, Warwick, UK. is recovered as the most basal rhynchosaur taxon in many phylogenetic analyses (e.g. Dilkes, 1998; Hone & Benton, 2008), and is represented by excellent cranial and postcranial material. It lacks the well-developed COMPUTED TOMOGRAPHIC SCANNING tooth plates that are typical of later rhynchosaurs. By SAM-PK-K10159 was scanned in the Museum für contrast, H. browni is known from relatively fragmen- Naturkunde Berlin with a Phoenix|X-ray Nanotom (GE tary material and is considerably less well under- Sensing and Inspection Technologies GmbH, Wunstorf, stood, but does possess expanded and well-developed Germany) using a tungsten target and a Cu filter tooth plates. 0.1 mm thick in modus 0, averaging 3, skip 2. The scan Here, we describe a third taxon of basal rhynchosaur comprised 1440 slices with an exposure time of 1 s, from Subzone B of the Cynognathus AZ of South 85 kV, current of 400 μA, and a voxel size of 22.79 μm. Africa (Fig. 1). This taxon provides additional X-ray slices were reconstructed with the software insights into the early evolutionary history of the DATOS|X-RECONSTRUCTION v. 1.5.0.22 (GE Sensing clade, including cranial evolution, diversity, and and Inspection Technologies GmbH, Phoenix|X-ray) and biogeography. analysed in VG STUDIO MAX 2.1 (Volume Graphics, Figure 1. Geographical and stratigraphical setting of the type specimen of Eohyosaurus wolvaardti gen. et sp. nov. A, map of South Africa and surrounding regions showing the location of the farm Lemoenfontein 44 (marked with a star); B, simplified stratigraphy of the upper portion of the Beaufort Group (stratigraphical level of E. wolvaardti marked with a star). Abbreviations: CHANGH., Changhsingian; P, Permian. © 2015 The Linnean Society of London, Zoological Journal of the Linnean Society, 2015, 174, 571–588 NEW BASAL RHYNCHOSAUR FROM SOUTH AFRICA 573 Heidelberg, Germany). The specimen was too large to SYSTEMATIC PALAEONTOLOGY Downloaded from https://academic.oup.com/zoolinnean/article-abstract/174/3/571/2453122 by Universidade Estadual Paulista J�lio de Mesquita Filho user on 06 May 2019 be scanned in its entirety, so scans focused on areas DIAPSIDA OSBORN, 1903 SENSU LAURIN, 1991 of particular interest (tooth rows, endocranium). The ARCHOSAUROMORPHA HUENE, 1946 SENSU endocranial anatomy will be explored in detail else- where. A copy of the computed tomography (CT) data GAUTHIER,KLUGE,&ROWE, 1988 has been provided to the SAM, to be archived along RHYNCHOSAURIA OSBORN, 1903 SENSU DILKES, 1998 with the specimen. EOHYOSAURUS WOLVAARDTI GEN. ET SP. NOV. (FIGS 2–5) CLADISTIC ANALYSES Etymology Genus name from the Greek eos, meaning ‘early’ or In order to investigate the phylogenetic position of ‘dawn’, hyos, meaning ‘pig’ or ‘hog’, and sauros, meaning SAM-PK-K10159, a novel parsimony analysis was ‘lizard’ or ‘reptile’. Name refers to the common de- conducted based upon a modified version of the data scription of rhynchosaurs as ‘pig-reptiles’ and the early matrix of Montefeltro et al. (2013). The matrix of stratigraphical occurrence of the new taxon. The species Montefeltro et al. (2013) was originally constructed is named after Frederik Petrus Wolvaardt, who dis- in order to investigate relationships within covered the type and only known specimen in Decem- Rhynchosauridae. For the present analysis we expand- ber 2000. The name is therefore intended to translate ed both taxonomic and character sampling in order as ‘Wolvaardt’s early pig-reptile’. to allow us to address the relationships of both basal (non-rhynchosaurid) members of Rhynchosauria and Rhynchosauridae. Holotype We added two non-rhynchosaurian outgroups SAM-PK-K10159, partial skull missing the anterior end, (Prolacerta broomi and Protorosaurus speneri) and the with associated incomplete lower jaws (Figs 2–5). two currently recognized species of Rhynchosaurus (Rhynchosaurus articeps and Rhynchosaurus brodiei) Locality and horizon as discrete operational taxonomic units. By contrast, Farm Lemoenfontein 44, Rouxville District, Free State the postcranial material EXEMS 79/1992 from the Otter Province, South Africa. Burgersdorp Formation, Sandstone of the UK, previously referred to Fodonyx Cynognathus Assemblage Zone, Subzone B (early Middle spenceri (Hone & Benton, 2008), was not