Presencia del bóvido Austroportax en el yacimiento mioceno de Batallones-1 (MN 10, cuenca de Madrid, España)

Bovid fossils constitute rare findings in the Cerro de los Batallones fossil sites. However, maxillar and mandibular remains of a juvenile individual of a large-sized bovid were discovered in Batallones-1. In the present work, we describe these fossils and assign them to the Eurpoean genus Austroportax (Sickenberg, 1829). We name these fossils as Austroportax sp. due to the lack of more diagnostic additional material belonging to this form.


Introduction
Batallones-1 was the first of the 9 fossil sites discovered and excavated in the Cerro de los Batallones (Batallones butte), located in the South-Central area of the Cenozoic Madrid Basin.Cerro de los Batallones is constituted of a sedimentary sequence which comprises three units, all of them deposited in terrestrial environments during the early late Miocene.The fossil bones are included in a sedimentary matrix that cuts discordantly the three units of the butte (see Domingo et al., 2011 for a thorough geological characterization of the fossil sites in the butte).This fact led to the proposal that the fossil acumulation was due to the presence of cavities formed as a consequence of a pseudokarstic process known as piping (Pozo et al., 2004;Domingo et al., 2011).

Al measurements are given in mm.
Nomenclature: We use the terminology of Barone (1999) for the anatomical nomenclature of the cranial and mandibular skeleton, and that of Azanza (2000) for nomenclature of the dentition (English version in Sánchez and Morales, 2008).

Maxilla and upper dentition
Most of the external side of both maxillae is preserved, including part of the broad and well developed facial crest from which the masseter muscle originates.The infraorbitary foramen is relatively small, divided into two smaller foramina by means of a near-horizontal septum.The insertion crest for the buccinator muscle is very well marked, distally triangular and anteriorly narrow and elongated.
The deciduous premolars show a high degree of wear.The DP2 is elongated with well-marked labial cones that have a broad and deep valley between them.The DP3 is bi-lobed.It has a posterior lobe only slightly smaller than the anterior one, both the anterior style and the antero-labial cone are well developed, the mesostyle is strong, and both the postero-labial cone and style are small.The wellmolarized DP4 has a strong antero-labial cone and style, well developed mesostyle and moderately developed labial cone and style.There is a deposit of caementum on the labial wall of both DP3 and DP4.
The permanent cheek teeth have a medium-low degree of wear, so their morphology can be thoroughly described.The M2 is clearly bigger and more hypsodont than the M1.As in the DP3-DP4, both molars have a layer of caementum on the labial wall.The M2 has a strong parastyle which develops prominently from the labial wall.Both M1 and M2 have a well-marked labial paracone rib which fuses basally with the parastyle.The column-shaped mesostyle is also strongly developed.Neither the pre-protocrista nor the post-protocrista contact the labial wall.However, in the distal lobe of the molars the pre-metaconulecrista contacts the preparacrista, and the post-metaconulecrista contacts the post-paracrista at a medium height in the crown.The M3 in BAT1'05.D4-78 can be observed through the mandibular bone, not-erupted yet.It is morphologically very similar to the M2 but has a more developed metastylid.

Mandible and lower dentition
The hemimandible BAT1'04.D4-392 is almost complete, with both the horizontal and vertical branches preserved.It has two mental foramina, being the anterior one sub-circular and much big-ger than the posterior one, which is elliptic.The horizontal ramus is not too much high, but this could be a result of the juvenile condition of this individual.The masseteric fossa is shallow.The angular process is rounded and broad, well individualized.The tip of the coronoid process is fragmented, however the process appears to be relatively short and broad with a marked curvature.The processus condilaris has a slightly concave rectangular articulation surface, the medial ramus of which is more developed than the lateral one.The mandibular foramen is subcircular.The crest posterior to the mandibular foramen which marks the upper insertion border for the medial pterygoideus muscle is very well developed.The pterygoideus pit is shallow.
The right i1 is preserved, still un-erupted.As it was the case with the deciduous upper dentition, both the dp3 and dp4 of the hemimandible BAT1'04.D4-392 are heavily worn-out.The dp3 has a very developed mesolabial conid and a strong mesolingual conid.The anterior wing is double (well separated anterior stylid and anterior conid).The three lobes in the dp4 increase mesio-distally their bucco-lingual width.The buccal wall has traces of caementum.The antero-labial conid is separated from the meso-labial conid by a shallow valley, however the latter is strongly separated from the postero-labial conid.There is a faint 'metastylid' and a strong postero-labial stylid.The meso-lingual conid has two well developed stylids, both of them showing caementum deposits.The caementum covering is also present in the lingual and buccal walls of both m1 and m2.The m1 has a well developed mesial cingulid and a columnshaped ectostylid.The metastylid is moderately developed and the lingual separation between the metaconid and the entoconid is abrupt and wide, well marked.The m2 is larger and more hypsodont than the m1, with a less developed mesial cingulid and ectostylid.Both molars show flattened lingual cusps with non-aligned cristids.The post-protocristid fuses with the pre-entocristid and the prehypocristid.Although the m3 has not erupted yet, the non-aligned position of the lingual cusps is clearly visible.

Discussion
One of the most conspicuous features of the Batallones-1 bovid is its large size, which exceeds  Stromer, 1928 andMiotragocerus pannoniae (Kretzoi, 1942).The exception is the large sized Austroportax latifrons (Sickenberg, 1929), from the Austrian site of Hollabrunn.Moyà-Solà (1983) included into this species additional fossils from the Spanish Vallesian, including dental material of equivalent size to that of the Batallones-1 sample.This material comes from the sites of Ballestar (MN 9), Hostalets de Pierola superior (MN 9) y Terrasa (MN 10) all from the Vallès-Penedès Basin in Spain.However, the Batallones-1 bovid is still larger than the cf.Austroportax from Ballestar and Hostalets de Pierola.
The dental morphology of the Batallones-1 bovid is a mixture of apparently conservative and advanced characters.As in basal forms such as Eotragus, Batallones-1 bovid has upper molars with well separated lingual lobes and well developed styles.Also, the lower molars have relatively strong ectostylids, the lingual cusps are not aligned, and the metastylids are well developed.In all these features it recalls a more hypsodont and very large version of Eotragus.However, the presence of the caementum covering in the permanent molars is an advanced feature hitherto not described in the genus, so it could be either an autoapomorphic feature of the Batallones-1 bovid or a preservation / preparation bias in the remaining Austroportax fossils.The dental morphology of the Batallones-1 bovid studied herein is very similar to that described by Moyá-Solá (1983) for his Austroportax sp. from Terrasa and Ballestar.Thus, taking this into account together with the large size, we decided to assign the bovid remains from Batallones-1 to the genus Austroportax.