Hispanodorcas Thomas, Morales, and Heintz, 1982

Kostopoulos, Dimitris S., 2014, Taxonomic re-assessment and phylogenetic relationships of Miocene homonymously spiral-horned antelopes, Acta Palaeontologica Polonica 59 (1), pp. 9-29 : 11

Genus Hispanodorcas Thomas, Morales, and Heintz, 1982

Type species: Hispanodorcas torrubiae Thomas, Morales, and Heintz, 1982 ; see below.

Emended diagnosis (modified from Thomas et al. 1982; Bouvrain and Bonis 1988).—Plesiomorphic traits: small−sized bovids with short, thin, and gradually tapering horncores; horncores inserted above the orbits, weakly inclined posteriorly with a straight or gently curved posterior edge, and situated relatively far apart on the frontals; frontals without sinuses and not raised above the level of the orbits; basioccipital narrowing anteriorly. Apomorphic traits: weakly developed homonymous twisting (1/2 coil) of the horncores; anterior keel poorly developed; horncores more strongly divergent distally than proximally, and bearing a variably wide and shallow lateral depression (i.e., a broad sulcus) dividing them into a smaller anterior and a larger posterior portion; horncores transversely compressed at the base (compression index 70–85%; Fig. 1 ), with a flattened lateral surface and a strongly convex medial surface; frontals moderately thick anterior to the horncores, and moderately to strongly flexed in lateral profile; pedicles very short; postcornual fossae situated laterally; small to moderately−sized supraorbital foramina located within pits; basioccipital with a variably developed medial groove.

Remarks.— Hispanodorcas is presently known from three species ranging from the middle Turolian to the early Ruscinian ( MN 12–MN14) ( Thomas et al. 1982; Bouvrain and Bonis 1988; Alcalá and Morales 2006). Gentry et al. (1999) furthermore suggested that several Ukrainian specimens of early Turolian age usually referred to “ Gazella ” rodleri Pilgrim and Hopwood, 1928 might be allocated to Hispanodorcas (but see discussions in Bouvrain and Bonis 1988; Kostopoulos and Bernor 2011), whereas Kostopoulos (2006: 148) indicated that some bovid material from the latest Vallesian locality of Nikiti−1 ( Greece), previously ascribed to Oioceros ( Kostopoulos and Koufos 1996) , may in fact represent Hispanodorcas .

A character frequently used for defining Hispanodorcas is the presence of a lateral longitudinal groove on the horncore extending on to the pedicle and reaching the postcornual fossa. This feature, originally described by Thomas et al. (1982), became part of the emended generic diagnosis provided by Bouvrain and Bonis (1988). Although this groove is well marked on both the holotype of H. torrubiae ( Thomas et al. 1982: fig. 1, pl. 1: 1), and the left horncore of the holotype of H. orientalis ( Bouvrain and Bonis 1988: fig. 2), it is much less evident in some of the paratypes of H. torrubiae ( Thomas et al. 1982: pl. 1: 2), and almost absent in H. heintzi ( Alcalá and Morales 2006) and the material from Nikiti−1 described here. Furthermore, the same feature is also present in some specimens of Oioceros atropatenes ( Rodler and Weithofer, 1890) , as well as in the holotype of Samotragus occidentalis Masini and Thomas, 1989 , thus indicating that this groove may not be diagnostic at the genus level. However, all known specimens of Hispanodorcas show a rather characteristic flattening on the lateral surface of the horncores. In most cases, this flattening appears as a wide and shallow depression ( Fig. 2A ) with a blunt anterior and a more pronounced posterior edge, with the latter forming a faint crest. In H. torrubiae and H. orientalis at least, this depression develops distally into a rather deep furrow ( Fig. 2B ).

Figures

Fig. 1. Box−plots of the horncore basal compression index (i.e., TD*100/ ADP) for several species and genera of Oiocerina, showing the medial (horizontal line inside the boxes), the 25–75% quartiles (gray boxes) and the minimum and maximum range of values (short horizontal lines). NKT−1, Nikiti−1; RZ1, Ravin des Zouaves 1.

Fig. 2. Oiocerin antelope Hispanodorcas orientalis Bouvrain and Bonis, 1988, from the late Turolian locality of Dytiko−3 (DKO), Axios Valley, Northern Greece, in lateral (A) and anterior (B) views of the holotype cranium LGPUT DKO−4. The arrow in A indicates an enlarged version of the same view, where the white lines indicate the extent of the lateral depression; the arrows in B mark the trace of the anterior keel.