Palaeont. afr., 34, 33-42 ( 1997) A REASSESSMENT OF EUNOTOSAURUS AFRICANUS SEELEY (AMNIOTA: PARAREPTILIA). by C hris E. Gow Bernard Price Institute f or Palaeontological Research, University of the Witwatersrand, Johannesburg, Private Bag 3 , Wits 2050, South Africa ABSTRACT This paper provides an almost complete description of the Permian fossil reptileEunotosaurus for the first time. Taphonomy indicates that these were terrestrial animals; dentition suggests that they preyed on small invertebrates; while the broad, imbricating ribs point to a slow moving animal with a protective, turtle-like carapace. Temporal emargination and the fan-like iliac blade serve to align these animals with Para reptilia, sensu Laurin and Reisz ( 1995). Eunorosaurusand mi llerettids are sister taxa on the basis of stapes and rib morpho logy, and together they constitute the sister taxon to Ankyramopha (Debraga and Reisz 1996), having eight character in which they are less derived than the latter. KEYWORDS: Eunotsaurus, parareptiles INTRODUCTION MATERIAL AND METHODS The late Permian reptile Eunotosaurus africanus Renewed interest in Eunotosaurus arose with the Seeley 1892, was revised by Cox (1969), and the discovery of a large specimen which has a skull and first and only good skull was described by Keyser pectoral girdle and anterior part of the trunk, all in and Gow (198 1). The available material has generally articulation - M777 in the collections of the Council been too poor to yield detailed, definitive information for Geosciences (formerly the Geological Survey), about the osteology, biology, and relationships of Keyser & Gow 1981). This specimen has well the animal. The limbs in particular have remained preserved bone in a very hard, fine grained, green poorl y known unti l recently (Gow and De Klerk mudstone matrix: it was mechanically prepared at 1997). the Council for Geosciences, and unfortunately Great advances have been made in the study of separation between hard matrix and softer bone is amniote phylogeny in recent years, yet much remains poor, with the result that much surface detail, such as to be done. ornamentation of the dermal bones of the skull, was According to recent work of Laurin and Reisz lost during preparation. (1 995), and Debraga and Reisz (1996), Amniota is Subsequently J. W e iman recovered a small comprised of three major monophyletic groups, plus articulated specimen form the Free State (NMQR the poorly understood Mesosauridae. 3299 in the collections of the National Museum, These groups a re, i) Synaps ida including Bloemfontein) which is extremely poorly preserved, mammals, ii) Eureptilia, including living re ptiles the mudstone matrix being deeply weathered, and except testudines and birds, and iii) Parareptilia the weathered and eroded bone in very poor including testudines. These groups diverged condition; it includes a partial skull lacking braincase approximately 300 million years ago in the Upper and palate, and with maxillary teeth represented by Carboniferous: mesosaurs and parareptiles have no impressions only; much of the trunk including parts fossil history prior to the Middle Permian. of both limb girdles, and parts of the forelimbs. The Early amniotes share numerous plesiomorphies, main value of this specimen is that it confirms some and it has not been easy to find synapomorphies of the sutural details of the skull roof as determined defining the major groups, for example, Laurin and from M777. Reisz (1 995) listed 14 apomorphies for Pararepti lia, In 1995 the Albany Museum, Grahamstown, while Debraga and Reisz ( 1996) halved this number. acquired an excellent specimen (AM5999) from the Eunotosaurus has been so poorly known that it Eastern Cape (Gow & de Klerk 1997). This small has had to be omitted from most recent phylogenetic specimen exists mostly as high fidelity impression in studies; Lee (1993) however, has expressed the a block of fine grained sandstone; it is headless, but opinion that it is a synapsid. The present tudy has most of the limbs, including a partial manus and clearly demonstrates that it is a good parareptile, compete pes, and a tail which is almost complete. sharing several deri ved characters with the slightly Several other specimens are represented in various younger millerettids. museum collections, but generally consist of only 34 the carapace-like trunk portion comprised of M777 is slightly dorso-ventrally crushed. Some articulated vertebrae and ribs: in some cases it appears ornamentation is preserved on the National Museum that parts of these specimens may have bee n skull (NAMQR3299); Figure 3 attempts to illustrate overlooked in the field (this is mentioned as a caution this. for the future rather than a criticism of past collecting). The skull is triangular in dorsal view, quite deep, The matrix of some specimens is so heavily indurated and blunt-snouted, with a backwardly sloping occiput. as to defy preparation. It is superficially similar to that of modern tortoises. Specimens which add useful informati on are:­ The pattern of tuberosities is closely comparable to GM71 in the collections of the Counc il for that seen in millerettids, a character regarded by Geosciences, being a block of articulated mid-dorsal Laurin and Reisz (1995) as an autapomorphy of vertebrae and ribs, which also has six dissociated mi llerettids. caudal vertebrae; and a small unnumbered specimen Nothing useful can be said about the lower jaws as from the same collection which includes parts of a they are damaged and show hardly any sutural macerated skull. The BPI material (BP/l/3516) which detail. had been acid prepared by Cox (1969) has also been examined. Premaxilla. Eunotosaurus occurs in the upper half of the The premaxillae meet the nasal above, and have Tapinocephalus assemblage zone and throughout oblique sutural contacts with the maxillae laterally the Pristerognathus assemblage zone of the Beaufort below the nares. It is difficult to estimate the original (Smith & Keyser 1995). According to Roger Smith size of the nares as their margins are damaged. Each (pers. com.) Eunotosaurus specimens are always premaxilla bore three sharply pointed teeth, circular preserved in crevasse splay situations, e ither in in cross section. mudrocks, or less commonly fine-grained sandstone. Being broad bodied they are invariably preserved Maxilla. lying on their ventral surface. The facial region is damaged, so the outlines of the Specimens have been variously pre pared as maxillae as illustrated are not true surface suture appropriate: Cox ( 1969) had some success with lines. Posteriorly both maxillae are slig htly acetic acid, extensive use has been made of incomplete, and, because of this and the effects of mechanical preparation, and the Albany specimen distortion, it is not possible to determine their true was studied by means of latex peels and X-rays. relationship to the jugals: I would not like to have to However, some material simply cannot be adequately decide whether or not the maxillae enter the orbits. In prepared with currently available techniques. this specimen there are approximately 20 tooth positions in the maxilla: maxillary teeth are smaller DESCRIPTION than those of the premaxilla; they are also rounded in The Skull. Figures 1, 2, 3 & 4. section and taper to a point, they decrease in size This description refers to the specimen M777, posteriad; gaps between teeth indicate ongoing except where otherwise stated. It is important to replacement. appreciate that mos t of the dorsal s urface ornamentation of the skull of M777 was removed Nasal, lacrimal and prefrontal. with the matrix, and that much of the surface of the These elements are so badly damaged that nothing occiput adheres to the matrix attached to the main useful can be said about the superficial relationships: block. Also important to note is that at some stage the the lacrimal region (but not the prefrontal) was skull roof of M777 was broken off and reattached prepared in the left orbit, where the lacrimal canal with a thick layer of epoxy cement. The skull of can be seen. Figure I . Eunotosaurus M777 Dorsal and ventral views of the skull. Dense texturing is matrix, more open dots indicate epoxy cement. 35 Pot p Frontal. The frontals are large, bordered anteriorly by the nasals, laterally by pre- and postfrontals, and posteriorly by the parietals. Their dorsal surfaces are sculpted. It is not possible to determine if they were excluded from the dorsal rim of the orbit by pre- and postfrontals. Parietal. The parietals form the broadest part of the skull table: they surround a fairly large pineal foramen. The parietal makes sutural contact with the frontal anteriorly, postfrontal, postorbital and supratemporal laterally, and curves onto the occiput to meet the postparietal and tabular. The parietals overlap the dorsal part of the supraoccipital: this is seen in QR3299 where the parietals are damaged in this region. Postfrontal. Large postfrontals straddle the fronto-parietal suture dorsolaterally and make sutural contact with the postorbitals laterally (bones of the cheek region are displaced in M777 due to distortion and virtually absent in QR3299). Postorbital. This is a robust element with a distinct lateral tuberosity. It is in sutural contact with the postfrontal anteriorly, the parietal and supratemporal dorsally 1cm and the jugal posteriorly. Figure 2. Above. Lateral views of Eunotosaurus skull M777. J ugal. Dense texturising is matrix, more open dots indicate Relationships of the jugal cannot be satisfactorily epoxy cement. Below. The stapes of Eunotosaurus determined as only the left jugal of M777 is preserved, M777 left, compared with M i/leretta B P/ I /3821 on the right. p F:of F :t,. ·:-:t...\ p 1cm Figure 3. Eunotosaurus QR3299. Dorsal, lateral, and occipital views of the skull roof. Dense texture is matrix. 36 Pot p Survey specimen (Figure 4) has macerated skull, inc luding a perfect left squamosal with external St surface exposed, showing that this bone had a recess 1cm Sq whi ch contributed to the otic notch exactly as in millerettids.