Antilopinae ( Bovidae , Mammalia ) from the Lower Pliocene of Teruel Basin ( Spain )

Two genera of Antilopinae are identified in the Lower Pliocene localities of the Teruel Basin: Hispanodorcas and Gazella. Hispanodorcas is represented at La Calera by a new species, Hispanodorcas heintzi nov. sp., which is characterised by the development of a strong anterior keel in the horn cores. Gazella is represented in La Calera and Villalba Alta localities by a new species, Gazella soriae nov. sp., which is defined by its small size and weak transversal compression of the horn cores. A species smaller than Gazella soriae, Gazella baturra nov. sp. is identified at La Gloria 4.


Introduction
Bovids and Hipparion are the most important components of the Spanish large mammal associations from the beginning of the Upper Miocene until the end of the Pliocene (Alcalá, 1994).The bovid assemblage recognised in the Lower Pliocene localities of the Teruel Basin consists mainly of species belonging to the subfamilies Hippotraginae and Antilopinae.The association of these two bovid groups seems constant during the Early Pliocene.Nevertheless, in the Upper Pliocene localities, the Hippotraginae disappears and Gazella, represented by the typical Villafranchian species Gazella borbonica, remains as the most frequent bovid.The study of the Lower Pliocene Antilopinae is the aim of this work.
Diagnosis -Hispanodorcas heintzi is a species larger than Hispanodorcas torrubiae.Horn cores with torsion of Oioceros type, inserted on the frontal with a curvature backwards and towards the exterior part.The cross-section is elliptic with a strong medio-lateral compression.It also shows a strong anterior keel and smooth external groove.
Differential diagnosis -Hispanodorcas heintzi differs from H. torrubiae and H. orientalis by the development of an anterior keel and the smaller size of the external groove in the horn cores.Additionally, it differs from H. torrubiae by the strong medio-lateral compression of the horn cores and its cross-section of elliptical shape.

Description
Holotype (LCA-81-234): Frontal bone fragment with the two horn cores (fig.1; Pl. 1, fig. 1).These are inserted directly above the orbits and their pedicle is very short.The frontal is thick.The supraorbital foramen is strong and placed near the base of the horn core.The horn cores are separated by 27 mm.The cross-section of the horn core at the base is elliptical, with a strong transversal compression and with the antero-posterior axis oblique with respect to the sagittal axis of the frontal bone.The insertions of the horn cores on the frontal are inclined backwards and laterally.The horn cores, with torsion of Oioceros type, have a strong anterior keel and a smooth external groove, but they do not complete a turn.Other specimens of horn cores, such as LCA-81-229 and LCA-81-159, show a similar developed anterior keel and weak grooves on both sides (Pl. 1,. Dentition: The dental morphology of Hispanodorcas heintzi (Pl. 1, fig.4-5) is remarkably close to that known for the gazelles found in the same locality (Pl.2, fig.4-5, table 1), differing mainly by its greater size and lesser hypsodonty, the reduction of the premolar row with respect to the molars and the presence of a distinct metaconid in P 4 .

Discussion
Hispanodorcas heintzi shares several characters horn cores with moderate torsion of Oioceros type, presence of a continuous groove in the external face, and Gazella type dentition -with the other two known species of the genus, H. torrubiae, the type species, defined by Thomas et al. (1982) in the Middle Turolian Spanish locality of Concud and H. orientalis from the Upper Turolian of Dytiko in Greece (Bouvrain & Bonis, 1988).It further shares with H. orientalis the curvature of the horn cores inclined backwards and their basal divergence.These characters are not known with precision in H. torrubiae.
The new species from La Calera differs mainly from the other two mentioned species in the development of an anterior keel in the horn cores and, in some specimens, of a posterior one, too.Additionally, the continuous groove of the external side is less developed, and the transversal compression of the horn cores is clearly greater than in H. torrubiae, but in this character it is not different from H. orientalis.
Diagnosis -Gazella with small horn cores of a rounded cross-section.Females with smaller horn cores, which are straighter and with a more rounded transversal section than the male ones.Differential diagnosis -Gazella soriae differs from Gazella borbonica and Gazella deperdita by the smaller size of the male horn cores, and the lesser degree of transversal compression; it differs from Gazella deperdita by the presence of horn cores in the female specimens, it differs from Gazella baturra and Gazella thomasi by its larger size.

Description
Holotype (LA-471): Horn core belonging to a male animal, it has the pedicle but lacks the apex (Pl.2, fig.1).As in the rest of the specimens, it is remarkable for its gracility.The cross-section is oval-shaped, with the lateral side a bit more flattened than the medial one.The horn core is slightly curved backwards and the compression increases slightly towards the apex.The surface is ornamented with many grooves and wrinkles of different sizes.
Horn core LA-463/464 (Pl.2, fig.3): It belongs to a male animal.It differs from the holotype because it is straighter and by its less compressed cross-sec- tion.Other male horn cores fall within the range of variation of the two specimens described above, except in size, the range of which is represented in figure 2 and table 2.
Horn core LA-465: Horn core of a female animal, which is easily distinguished from the male specimens because of its much smaller size, a more rounded section, a lesser backward curvature and smoother ornamentation (Pl.2, fig.2).
Other localities: Villalba Alta (Teruel, Spain, MN 15): a horn core corresponding to a male animal.It is morphologically similar to LA-463 from La Calera, except for its larger size (DAP Base = 25.8 mm, DT Base = 20.2mm) which reaches the maximum known size for this species.Montpellier (France, MN 14): an incomplete horn core described by Heintz (1970) could probably be included in this new species.
Diagnosis -Gazella with horn cores of small size, rounded cross-section, and small lateral compression.Differential diagnosis -Gazella baturra differs from the other known Miocene and Pliocene gazelles by its smaller horn cores, teeth and postcranial bones.Gazella baturra differs from Gazella thomasi of the Upper Pliocene of North Africa by the lesser lateral compression of its horn cores.

Description
Holotype GL-231: Nearly complete right horn core.It is almost rectilinear, with a weak backward curvature.The external side is a bit flatter than the internal one.The cross-section is weakly compressed and oval-shaped.The horn core is ornamented with grooves and wrinkles, particularly the external side (Pl.

M F
Horn core GL-408: Specimen similar to the previous one, except the ornamentation, which is smoother and there is a small medial keel near the apex (Pl.3, fig.3).The other horn cores are morphologically similar to these ones (Pl.3, fig. 2).
Dentition: It is the typical of the genus Gazella, differing from Gazella borbonica by its smaller size (Pl. 3,.
Gazella baturra and Gazella soriae, together with Gazella thomasi (see Geraads & Amani, 1998), are among the smallest species of the the genus, in particular the first of them, which is probably the smallest species known until now.Apart from size, the morphology of the horns is similar (rounded section, with weak transversal compression, strong ornamentation, etc.).In these characters they are closer to Gazella deperdita, but this species has a sexual dimorphism in which female animals lack horns (Heintz, 1969).In contrast, Gazella soriae -as in most of the extant speciesmales and females have different sized horns.We do not have information about sexual dimorphism in Gazella baturra or Gazella thomasi because all the available horns are interpreted as belonging to male animals.Gazella soriae and Gazella baturra share with Gazella deperdita the small size of both the postcranial skeleton (Pl.3, fig. 9-11) and the dentition.For example, the length of the metatarsal in Gazella baturra is 135 mm, in Gazella soriae 148 mm and in Gazella deperdita it ranges between 146 and 150 mm.In addition, the mean length of the M 3 is 16.23 mm in Gazella baturra and 15.86 mm in Gazella deperdita (Alcalá, 1994 andHeintz, 1971, respectively).The evidence that Gazella baturra is not only a gazelle of small size, but also that it has small horns, seems clear.
The male horn cores of Gazella borbonica from Las Higueruelas (Heintz, 1975;Alberdi et al., 1984) have a smaller size with respect to the range recorded for the populations of Gazella borbonica from other localities, such as El Rincón 1, La Puebla de Valverde or Saint Vallier (France).Nevertheless, although it is situated in position intermediate between Gazella soriae from La Calera and typical Gazella borbonica, the transversal compression is similar that presented by Gazella borbonica, clearly distinguishable from the group of gazelles from La Gloria and La Calera.The classification of Las Higueruelas material as Gazella aff.G. borbonica is preferable pending a detailed study of the new material collected by Mazo (1993).
The gazelle horn cores from Piedrabuena and Layna were also classified as Gazella borbonica by Mazo & Torres, (1989-1990) and Torres & Mazo (1991).According to their size, in this study they are placed at the boundary of the variation of Gazella aff.G. borbonica from Las Higueruelas and the typical Gazella borbonica, their attribution to one or the other form being difficult.The specimens from Piedrabuena can be included in the same group of Gazella aff.G. borbonica without difficulty, but for those from Layna there is no clear criterion, except that the locality is older -Upper Alfambrian, MN 15 -than the typical localities with Gazella borbonica (Lower and Upper Villafranchian MN 16/17).Provisionally, the gazelle from Layna can be included in the same group as the gazelles from Piedrabuena and Las Higueruelas.
Other species of Pliocene gazelles such as Gazella postmytilini (Vekua, 1972), Gazella bouvrainae (Kostopoulos, 1996;Kostopoulos & Athanassiou, 1997) and Gazella emilii (Bouvrain, 1998), have horns similar in size to those of Gazella borbonica, but with a notably less compressed transversal section, such as that of Gazella sinensis.In this character Gazella baturra and Gazella soriae differ very much not only from these oriental species, but also from Gazella borbonica.
Gazella borbonica can be considered a typical species of the Villafranchian with a very wide geographical range spanning from Spain to Greece (Kostopoulos & Athanassiou, 1997).However, the other described species of the Spanish Pliocene are not known outside Spain; the only exception is the possible presence of Gazella soriae at Montpellier (France).

Table 1 .-Measurements in mm of the dentition of Hispanodorcas heintzi nov. sp. and Gazella soriae nov. sp. from La Calera
L: Length; B: Breadth.
3, fig.1).Gazella borbonica from La Puebla de Valverde and El Rincón.F (female specimens); M (male specimens).The individual points has been omitted for the benefit of clarity.

Table 2 .-Measurements in mm of the horn cores from La Calera, La Gloria 4 and Villalba Alta
DAP: anteroposterior diameter; DP: tranverse diameter.

Table 3a .-Measurements in mm of the lower dentition of Gazella baturra nov. sp. from La Gloria
L: Length; B: Breadth.