Hispanodorcas heintzi Alcalá and Morales, 2006

Kostopoulos, Dimitris S., 2014, Taxonomic re-assessment and phylogenetic relationships of Miocene homonymously spiral-horned antelopes, Acta Palaeontologica Polonica 59 (1), pp. 9-29 : 13-14

Hispanodorcas heintzi Alcalá and Morales, 2006

Holotype: Frontlet, CSIC LCA−81−234 ( Alcalá and Morales 2006: fig. 1, pl. 1: 1).

Type locality: La Calera, Teruel Basin, Spain.

Type horizon: Early Pliocene ( MN 14).

Diagnosis.—As in Alcalá and Morales (2006).

Differential diagnosis.— H. heintzi differs from other members of the genus in having horncores which are strongly divergent from the base, bear an anterior, and occasionally a posterior, keel, and are characterized by a reduced lateral depression in form of a weak, longitudinal groove.

Geographic and stratigraphic range.—Early Ruscinian (Early Pliocene) of Spain.

? Hispanodorcas pilgrimi ( Azanza, Nieto, and Morales, 1998)

1998 Samotragus pilgrimi ; Azanza et al. 1998: 378, fig. 1.

Holotype: Partial skull with frontals, CSIC MNCN/TO3−1000 ( Azanza et al. 1998: fig. 1).

Type locality: Toril 3, Catalayud−Teruel Basin, Spain.

http://dx.doi.org/10.4202/app.2011.0013

Type horizon: Late Middle Miocene ( MN 7/8).

Emended diagnosis.—Medium−sized species with rather thick, homonymously twisted horncores; horncores moderately compressed transversely ( Fig. 1 ), weakly torsioned, gently curved and inclined posteriorly, elliptical in cross section, and bearing a wide lateral depression; frontals low; braincase long and deep; basioccipital narrow, and bearing a medial groove.

Remarks.— Azanza et al. (1998) assigned the Toril 3 taxon to Samotragus based on (i) the open helical spiraling of the horncores, with an abrupt narrowing of the cross section in their upper half, (ii) the backward curvature of the horncore axes, and (iii) the V−shaped anterior extension of the horncores over the pedicles. Roussiakis (2003) already noted that characters (i) and (ii) were misinterpreted in the Toril 3 species, whereas character (iii) is occasionally present in species of other genera (e.g., Oioceros and Hispanodorcas ) and therefore not uniquely indicative of Samotragus .

Although the braincase of the holotype is strongly deformed, several features mentioned by Azanza et al. (1998), or observed directly on the illustrated material and some pictures kindly provided by the authors, clearly separate the Toril 3 species from Samotragus . The latter include a rather simple and barely pinched interfrontal suture; moderately protruding orbital margins; frontals not raised above the orbital level; a narrow basioccipital with a medial groove; weakly torsioned horncores spaced far apart on the frontals, inserted above the orbits, weakly inclined posteriorly, and faintly curved laterally in their preserved distal part; the absence of a well−delimited lateral furrow on the horncores, but presence of a depression on their lateral surface; an elliptical cross section throughout the length of the horncore, with the greater axis oriented anteroposteriorly at the base and transversely along the preserved distal portion; an almost straight posterior edge of the horncores in lateral profile; and horncores with strong posterior and lateral basal relief.

This set of characters, and especially the wide, shallow and gently concave depression deepening upwards on the lateral surface of the horncores, clearly resembles Hispanodorcas . However, the Toril 3 taxon differs from other species included in this genus in its probably shorter and thicker horncores (about 40% larger in absolute basal dimensions than the largest known specimen of Hispanodorcas ), a less inclined face compared to the braincase, a rather deep braincase (instead of shallow as in H. orientalis ) and a groove running all along the basioccipital (instead of being restricted to its anterior portion as in H. orientalis ). Nevertheless, it seems that, out of the Late Miocene genera with homonymously twisted horncores, Hispanodorcas provides a better fit for the Toril 3 species than Samotragus . At the same time, similarities of the Toril 3 species with earlier bovids showing homonymous twisting are much less evident.

Geographic and stratigraphic range.—Astaracian (Middle Miocene) of Spain.

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.