Hippopotamodon antiquus ( Kaup, 1832 )

Geraads, Denis, Kaya, Tanju & Mayda, Serdar, 2005, Late Miocene large mammals from Yulafli, Thrace region, Turkey, and their biogeographic implications, Acta Palaeontologica Polonica 50 (3), pp. 523-544 : 534-536

Hippopotamodon antiquus ( Kaup, 1832)

Material from Yulafl I.—TTMEU−CY−45, symphysis with i1–i2 on both sides, bases of canines and right p1 (Fig. 10J); TTMEU−CY−49, right mandibular ramus with root of canine, and p3–m2 (Fig. 10K). Measurements are given in Table 4.

Description.—A slight overlap in the preserved parts of the dentaries show that the two specimens are not from the same individual.

Although the posterior border of TTMEU−CY−45 is missing, it is clear that the symphysis was short and stout. The incisors are inserted along a rather shallow arch, the line joining the alveoli of i1 and i3 being inclined at about 50 ° in respect to the sagittal line. There is a minute diastema between i3 and the canine, itself separated from p1, which is present on the right side only, by a very short diastema.

The incisors are robust but quite short, although they are only slightly worn, at their tips and along the lingual (dorsal) ridge of i1. The i2 is much broader than i1, and its flange, laterally offset, overlaps the labial face. The third incisor is missing on both sides, but was intermediate in diameters between i1 and i2. The length and relative position of the incisors, as well as the lack of diastemata, clearly point to a suid with a shortened muzzle.

The canine, rather vertically inserted, is imperfectly preserved, but it has an oval cross−section and a clear demarcation between crown and root. The latter, not being visible at the break just behind p1, must have been quite short, in sharp contrast to that of the other specimen (TTMEU−CY−49), and TTMEU−CY−45 is likely from a female individual.

The p1 is small but not vestigial (Fig. 10J). It is strongly compressed transversally, with a main tubercle, plus an anterior cuspid and several small ones along the main cristid. There are two fused roots.

TTMEU−CY−49: this specimen is broken in front of p2. Posteriorly, the symphysis reached at least the level of p3, and perhaps even that of p4. Although there is no direct evidence of it, the shape of the dentaries TTMEU−CY−45 + TTMEU− CY−49 suggests that the diastema between p1 and p2 was short. The canine, of which a part is preserved inside the bone, is much larger than that of TTMEU−CY−45, and therefore likely from a male individual. The cross−section is of verrucosus − type, with the following approximate widths (in mm) of the three sides: lingual = 20; antero−labial = 15; postero−labial = 15. The former two sides are covered with enamel .

Only the posterior root of p2 is preserved; all that can be said is that this tooth was rather large. The other cheek−teeth are in medium wear, except m1, which is in late wear. The p3 is a large and robust tooth, being even slightly longer than p4. Its morphology is simple, without any evidence of division of the main cuspid, which is inflated, especially labially; the talonid is expanded disto−labially into a strong vertical buttress. In lateral view; the steep slope of the anterior wear facet shows that the anterior accessory cusp was low, but it is also buttressed on both the lingual and labial sides. The p4 is stout and broad. As on p3, the anterior accessory cuspid is broadened. Comparisons.—The most common suid of the Mediterranean late Miocene is Microstonyx , whose systematics have long been debated. In the Turolian, in spite of the wealth of the material, recent reviews ( Bonis and Bouvrain 1996; Kostopoulos et al. 2001) have highlighted the difficulty to recognise two or more taxonomic entities. The variation range of the Pikermi m3s encompasses those of most of the other samples, except some Greek ones (Vathylakkos, Kerassia, Perivolaki), and no clear metric trend through time is evident. Therefore, we will include all of them in Microstonyx major . This species differs from the one present at Yulafli by a number of features: – the anterior part of the dentary is much more elongated so that, even though the symphysis is much longer, it does not reach farther posteriorly than the level of p2, and usually remains more anterior. The i3 is more posterior relative to i1–i2; there is a diastema between i3 and the canine, and a very long one between the latter and p2. – i1 and i2 are much longer, adding to the long slender as−

pect of the symphysial area, which much contrasts with that of the Yulafli specimen. This difference has also been mentioned by Made (2003). The i2 is not so broad relative to i1. – the canine is much smaller (it may even be missing), the difference being more marked in the male.

– p1 is always missing.

– p2 is smaller.

– the premolars are smaller, and p3 is shorter relative to p4

( Fig. 12 ), but its anterior accessory cuspid is higher and narrower.

– p4 is narrower, especially anteriorly, although some specimens approach the condition seen at Yulafli. This tooth,

which is rather variable in M. major , especially in the de−

velopment of the “Innenhügel” does not significantly differ in other morphological features.

Therefore, the Yulafli suid cannot be referred to M. major . It is much closer to the earlier species antiquus , often included in the same genus, or in Hippopotamodon Lydekker , or in Limnostonyx Ginsburg , of which it is the type−species. Following most recent authors, we will regard both latter generic names as synonymous, and include antiquus in it. Bonis and Bouvrain (1996) gave a clear account of this species, and we will follow their conclusions here. Besides the type locality, Eppelsheim, well−documented reports of this species are from Montredon in France ( Ginsburg 1988) and perhaps from Sophades in Greece ( Thenius 1955) although, as noted by Kostopoulos et al (2001) the teeth from Sophades are small. Bonis and Bouvrain (1996) also referred to this species some teeth from Akkirma, a site of unknown age near Ankara, and the anteriorly broadened premolars described by Senyürek (1952) support this identification. Further material of this species in Turkey includes a dentary MTA− 2388 from Bayraktepe, and a dentary MTA− 1964 from “ Uşak ”. The latter locality is very imprecise but, as this dentary is very different from those of Kemiklitepe, one of the main sites close to Uşak, Akçaköy is a more likely provenance. A few more specimens come from Sinap Tepe, near Ankara. MTA− 1955 (or 1953) displays the lower incisors, set in a shallow arch, and without any diastema between them and the canines, which are large. In the MNHNP, the holotype of Dicoryphochoerus meteai Ozansoy, 1965 , from Yassiören, is a complete right dentary. The i2 is much larger than i1; there are only very short diastemata between i3 and the canine, and between p2 and p1, which is long and bi−rooted. The p3 is long, and p4 is broad. All these specimens, in contrast to M. major , share the features observed in the Yulafli specimens.

These differences between H. antiquus (including the Yulafli suid) and M. major far exceed those between any two Turolian samples of Microstonyx . Even if there is only one species of this genus in the Turolian, we find it difficult to include antiquus in the same genus, as the differences between the two species would be far greater than between two living suid species (e.g., Sus scrofa / S. barbatus , Phacochoerus aethiopicus / P. africanus ), and we prefer to use Hippopotamodon . Indeed, pending detailed phyletic analysis, there is no evidence that H. antiquus and M. major form a monophyletic group. We agree with Bernor and Fessaha (2000) that “There is little data supporting its [ Microstonyx ] transition in MN10 from Hippopotamodon antiquus .”. In sharp contrast to Indarctos , for instance, no intermediate form is known, and Microstonyx is more likely to be a Turolian immigrant into Europe and the Eastern Mediterranean.

In any case, there is a clear chronological distinction between both genera, Microstonyx being known only in Turolian−equivalent sites, while all sites with H. antiquus are earlier.

Figures

Fig.12. Length vs. width plot of p3s and p4s in Hippopotamodon antiquus and Microstonyx major.