Inostrancevia africana Kammerer 2023

Inostrancevia africana Kammerer et al., 2023 Referred Specimen: PPM2018-7Z. Revised diagnose: In addition to the diagnose given by Kammerer et al. (2023), Inostrancevia africana is distinguished by the presence of rugosity and small foramina on the lateral face of the prefrontal. General aspect of the skull: Specimen PPM2018-7Z is a large partial skull, which preserves the skull roof, occiput, and a small portion of the posterior part of the basicranium. The skull appears to have undergone dorsoventral compression and mediolateral shearing, as evidenced by the dislodging of the ventral part of the maxilla into the skull roof and the posteroventral displacement of the right zygomatic arch, respectively (Fig. 3). Furthermore, the skull is traversed by a fracture through the parietalfrontal suture, and another vertical fracture separates the occiput from the dorsal half of the foramen magnum, possibly obliterating the nuchal ridge (assuming that this structure was present in this specimen). Anteriorly, the skull is crushed at the level of the prootics such that the pila antoticae are not preserved, together with the majority of the parasphenoid rostrum. The palate is not preserved. Only the large left canine is preserved. Identification Inostrancevia africana is diagnosed by the presence of an orbit larger than the temporal fenestra (11 cm vs. 9 cm, respectively); extreme narrowing of the jugal below the orbit (compared to I. alexandri); a far posterior position of the pineal foramen; a reduced contribution of the frontal to the orbital margins; the presence of a deep parietal depression; an anteroposteriorly greatly expanded postorbital bar ventrally, the protrusion of the postfrontal onto the parietal; and the laterally facing temporal bar of the squamosal. Locality and horizon Specimen PPM2018-7Z was found in the Lago district, near the Mepoche Locality, nearly 3 km northwest of the town. It was collected along one of the branches leading to the Maluízo River, a site corresponding to the K 6a2 Member of the K 6 Formation of the lithological sequence in the Metangula graben (Verniers et al., 1989). The detailed geology of the K6a2 Member is discussed in Araújo et al. (2020). This specimen was embedded in coarse-grained arkosic sandstones (Fig. 1). The K6a2 Member has produced many therapsid taxa such as Daptocephalus cf. D. leoniceps and Dicynodontoides / Kingoria, enabling correlation to the fauna of the Daptocephalus AZ in the Karoo Basin of South Africa (Araújo et al., 2020; Macungo et al., 2023). Skull measurements Anatomical descriptions Dentition Specimen PPM2018-7Z was found associated with a large, mediolaterally compressed left canine, and a badly preserved cross-section of the right canine. Only the crown of this tooth is preserved as the root is broken (Fig. 2). The preserved portion of this canine is 113 mm long (apicobasally), 32 mm wide at the base and 0.3 mm wide at the tip (mesiodistally). It bears fine serrations along the mesial and distal edges, here identified as denticles (de) following the standard therapsid tooth nomenclature (Hendrickx et al., 2015; Hoffman et al., 2023; Liu & Yang, 2022). The canine is curved distally. Its crown base is wide but it gradually tapers apically, as in other gorgonopsians (Fordyce et al., 2012; Kermack, 1956; Liu & Yang, 2022). A shallow depression (lid) is present on the lingual surface (lifa) of the crown base in PPM2018- 7Z, but the rest of the base has a gently convex surface. Towards the apical margin, the lingual face of this canine is flat (Fig. 2). The labial face of the crown is marked by many longitudinal low ridges that merge apically (apr). The mesial and distal edges of the canine of PPM2018- 7Z have transversely thick carinae that extend apicobasally. The mesial carina (mec) is shorter than the distal one (dic), as the former does not reach either the apical nor basal ends of the crown (Fig. 2). The carinae bear denticles. Although affected by large cracks, the mesial denticles are thick basally but become smaller apically in PPM2018-7Z. The density of the distal denticles increases apically and basally. The specimen PPM2018-7Z has only two postcanines (Fig. 3). These postcanines are large and elliptical (long axis oriented anteroposteriorly) in cross-section. They are clearly separated each other and from the canine. Only the root and a very small portion of the crown of the first postcanine is preserved. The second postcanine is completely preserved and does not bear serrations. Maxilla The maxilla is preserved as a small posterior portion of the left bone (max), which is attached to the skull, and an isolated and fragmentary right maxilla (Figs. 3, 4). Because of the dorsoventral compression of the skull, most of the lateral wall of the left maxilla is exposed in ventral view. The maxilla is tall and contacts the lacrimal and jugal posteriorly, the nasal dorsally, and the prefrontal posterodorsally. Laterally, the dorsalmost portion of the maxilla is pitted and is traversed by fractures, while the ventral portion is irregular and bears a deep depression (maxhd). This depression widens posteriorly and terminates at the contact between the maxilla and the jugal. Whether this depression is an anatomical feature (i.e., preorbital fossa) or an artefact cannot be determined because the specimen underwent significant distortion and compressions. The lateral face of the right maxilla is excavated by a shallow depression (mxld) on its anteroventral margin, immediately posterior to the canine (Fig. 3). This depression is flanked by the maxillary bulges that accommodate the canine and postcanines. Lacrimal The lacrimal (la) is preserved on both sides and forms the anterior border of the orbit. While the right lacrimal is largely complete despite being affected by cracks, the left lacrimal preserves only the dorsalmost part of the bone. The left lacrimal is mostly visible in ventral aspect due to deformation. The lacrimal forms the lateral face of the preserved portion of the snout. It is topped by the prefrontal, and both bones share a long, anteroposteriorly extending suture in lateral view. The lacrimal has a broad posterodorsal process that forms the entire anterior wall of the orbit in ventral view (Fig. 4C). This process forms an interdigitating contact with the prefrontal. As does the prefrontal, the lacrimal bears irregular depressions inside the orbit. Inside the orbit, the lacrimal is perforated by a circular lacrimal foramen (laf). The suture with the jugal is unclear, but this contact seems to follow an oblique orientation. Jugal In Specimen PPM2018-7Z, the right jugal (ju) is anteroposteriorly elongated, dorsoventrally tall, and mediolaterally compressed (Fig. 5). It extends anteriorly to form the posteroventral rim of the orbit and receives the postorbital bar along its posterodorsal surface. It is overlapped by the zygomatic process of the squamosal posteroventrally. The jugal is truncated anteriorly such that it forms only a small contribution to the suborbital bar is preserved. However, judging from the preserved portion, it is possible that the jugal would have formed the entire ventral border of the orbit. The jugal has an extensive medial contribution to the subtemporal bar as it extends far posteriorly, extending for nearly the entire anteroposterior length all of the temporal fenestra (jutp, Fig. 5B), more than in Arctognathus curvimola where it borders only the anterior half of the temporal fenestra (Kammerer, 2015). Only a small portion of the left jugal is preserved in contact with the lacrimal and is traversed by fractures (Fig. 4C). Below the postorbital bar, the jugal is dorsoventrally short in lateral and medial views (Fig. 5A, C). Due to this shortening of the jugal, it does not develop a distinct postorbital process in PPM2018-7Z, which is characteristic of the clade Gorgonopsia (Rubidge & Sidor, 2001). Fig. 4 (See legend on previous page.) Nasal Only a small portion of the nasal (na) is preserved anterior to the frontal in PPM2018-7Z (Fig. 4). The nasal shares a sutural contact with the frontal posteriorly and overlaps the maxilla along a straight anteroposterior contact laterally. The lateral margins of the nasals are raised to form low longitudinal ridges (nar). Between these ridges, the dorsal surface of the nasal bears thin anteroposterior crests that extend posteriorly onto the frontal. Similar longitudinal crests are present on the ventral surfaces of the nasals. Prefrontal The prefrontal is an elongated bone that tapers anteriorly in PPM2018-7Z. Its dorsal and ventral margins are smoothly convex at the sutural contacts with the frontal and lacrimal. As in other gorgonopsians (Boonstra, 1935; Kammerer et al., 2015, 2023; Kammerer, 2015, 2017b; Laurin, 1998; Olson, 1937), the prefrontal extends anteriorly beyond the frontal (Fig. 4). Despite the taphonomic deformation, the sutures between the prefrontal, nasal, and frontal were not obliterated. Anteriorly, the right prefrontal is crushed but the left prefrontal inserts between the nasal, frontal, and maxilla, forming a convex anterior margin. Posteriorly, the prefrontal has a convex lateral margin where it borders the orbit dorsally. The orbital rim is slightly raised. A few foramina pierce the lateral surface of the right prefrontal in PPM2018-7Z. Due to poor preservation, only a small portion of the prefrontal is visible inside the orbit, and this portion forms an interdigitating contact with the lacrimal (Fig. 4C). Frontal The frontal is relatively well-preserved in PPM2018- 7Z, except for its right posteriormost margin, which is broken. It is long and expands posteriorly, resulting in a roughly trapezoidal shape (Fig. 4A, B). Unlike in rubidgeines, the frontal has a small contribution to the dorsal rim of the orbit in PPM2018-7Z; but this contribution appears smaller than in Arctops willistoni (Brink & Kitchingi 1953; Kammerer, 2017a). The frontal forms a roughl