Barendskraal, a diverse amniote locality from the Lystrosaurus Assemblage Zone, Early Triassic of South Africa

INTRODUCTION In 1935, a South African Museum field crew led by the late L.D. Boonstra recovered a small collection of Karoo fossils from the farm Barendskraal (an annexe of the original farm Klip Fonteyn 234), approximately 11 km south of Middelburg in Eastern Cape Province, South Africa. This collection consisted mainly of material belonging to the dicynodont therapsid Lystrosaurus and the archosauromorph reptile ‘Chasmatosaurus’ (= Proterosuchus), along with a small, bone-bearing nodule labelled ‘amphibian’. That nodule later proved to contain the partial skeleton of a new procolophonoid parareptile, Sauropareion anoplus (Modesto et al. 2001). In his compilation of tetrapod species distribution in the Karoo, Kitching (1977) listed four species from Barendskraal, namely Proterosuchus ‘vanhoepeni’ (= P. fergusi) and three species of Lystrosaurus, both index genera for the Lystrosaurus Assemblage Zone (Groenewald & Kitching 1995). Successive expeditions to Barendskraal in 2001 and 2002 by the authors, prompted by the description of S. anoplus, resulted in the recovery of additional procolophonoid material, which proved to be part of a diverse amniote fauna (Damiani et al. 2002) that we report fully in this paper. The Lystrosaurus Assemblage Zone is part of the succession of eight biostratigraphic assemblage zones that comprise the Upper Permian–Middle Triassic Beaufort Group of the Karoo Basin, South Africa (Rubidge et al. 1995), a sequence that is generally accepted as the standard for non-marine Permian and Triassic time (Lucas 1998). The Lystrosaurus biozone is the type fauna for the Lootsbergian Land Vertebrate Faunachron of Early Triassic age (Lucas 1998), and records the recovery of terrestrial vertebrate faunas following the end-Permian extinction event, the largest such event in Earth history (Erwin et al. 2002). Note, however, that the genus Lystrosaurus has also been documented in uppermost Permian strata (Smith 1995; Smith & Ward 2001), so that the biozone does not encompass the full stratigraphic range of the genus Lystrosaurus. The tetrapod fauna of the Lystrosaurus biozone is dominated numerically by the dicynodont therapsid Lystrosaurus, which comprises some 95% of its known fossils (Groenewald & Kitching 1995); the remaining fauna consists of dicynodont, cynodont, and therocephalian therapsids, procolophonoid and diapsid reptiles, and temnospondyl amphibians (Groenewald & Kitching 1995). The fauna recovered to date from Barendskraal, surveyed below, contains typical elements of the Lystrosaurus Assemblage Zone but is remarkable for the diversity of amniote taxa, which includes three newly described procolophonoid species (Modesto et al. 2001, 2003; Reisz & Scott 2002). In addition, material of Lystrosaurus is relatively scarce, in contrast to most other Lystrosaurus biozone localities where Lystrosaurus is the dominant fossil taxon recovered (Kitching 1977; Groenewald & Kitching 1995). No temnospondyl amphibian material has yet been recovered, despite intensive collecting efforts. All material recovered during the 2001 and 2002 field seasons is reposited in the Bernard Price Institute for