Hippopotamodon Lydekker, 1877

Kostopoulos, Dimitris S. & Sen, Sevket, 2016, Suidae, Tragulidae, Giraffidae, and Bovidae, Geodiversitas 38 (2), pp. 273-298 : 275-277

Genus Hippopotamodon Lydekker, 1877

TYPE SPECIES. — Hippopotamodon sivalense Lydekker, 1877 , by original designation.

Hippopotamodon cf. antiquus ( Kaup, 1833) ( Fig. 1 )

MATERIAL EXAMINED AND MEASUREMENTS. — Küçükçekmece West: Partly preserved right?M1 (Wmesial lobe = 22.2 mm), MNHN.F.TRQ678; fragments of molars, TRQ676, TRQ677; right i3 (L = 18.0 mm; W = 7.6 mm), TRQ682; distal fragment of right dp4 (Wdistal lobe = 14.4 mm), TRQ679; distal part of a left p2 (Wdistal = 9.2 mm), TRQ681; left p3 (L = 22.4 mm; W = 12.3 mm),TRQ675; magnum,TRQ673 (H = 28.4 mm; TDmax = 30.1 mm).

DESCRIPTION AND REMARKS

While this work was in progress, part of the studied material appeared in Pickford (2015: 84; table 21; fig. 76), without, however, a detailed description and comparison. Though poorly represented in the Küçükçekmece West sample, we believe suids from this site merit a full presentation, especially as our opinion differs from that of the latter author.

Most of the Küçükçekmece West suids belong to a largesized suine from the extensively discussed but still unresolved taxonomic group centred on Hippopotamodon Lydekker, 1877 and Microstonyx Pilgrim, 1926 (for a detailed taxomonic history and divergent opinions see Made & Hussain 1989; Fortelius et al. 1996; Liu et al. 2004; Made et al. 2013; Pickford 1988, 2015). Avoiding taxonomic complications, we adopt here the point of view of Made & Hussain (1989), formally established by Pickford (2015), in recognizing synonymy between these two genera. In agreement, however, with Liu et al. (2004), we regard Hippopotamodon major (Gervais, 1848) as a polymorphic species including Sus erymanthius Roth & Wagner, 1854 . Dicoryphochoerus meteai Ozansoy, 1965 from Yassiören, Turkey is considered to be a junior synonym of H. antiquus ( Kaup, 1833) ( Fortelius et al. 1996) .

The single reasonably complete upper molar ( Fig. 1D ) lacks the metacone. Its length is estimated at about 24 mm. It shows a thick and complicated mesial cingulum with a rather clear central accessory cusplet. The lingual cingulum is also well expressed, especially around the hypocone, which appears multicuspid. The strong cingulum precludes an ascription to Propotamochoerus Pilgrim, 1925 and points to Hippopotamodon ( Pickford 1988) . Pickford (2015: table 21, fig. 76A) refers to this tooth as an M2 of Hippopotamodon major (distinct from H. erymanthius according to the same author) but if an M2 it would be placed far below the size range of this species, being even smaller than the smallest known M2 from Pikermi, Greece and within the size range of Propotamochoerus provincialis (Gervais, 1852) . In fact, as the tooth is completely unworn and lacks dentine, it is most probably an M1 still unerupted at the time of the animal’s death (van der Made pers. comm. 2015). In that case, it is metrically comparable to the largest known specimens of H. major (in our concept) and the smaller of H. antiquus (according to the size ranges provided by Made et al. 2013: fig. 6).

The i3,MNHN.F.TRQ682 from Küçükçekmece is quite worn ( Fig. 1A ; the same specimen was illustrated by Pickford 2015: fig.76C as a left I3with catalogue number MNHN.F.TRQ653). It is similar in occlusal length but broader than that of H. major from Axios valley, Greece (MNHN.F.SQL912: L = 19.5 mm, W = 5.8 mm), Perivolaki, Greece (LGPUT PER-265: L = 21.5 mm, W = 5.9mm) and Maragheh, Iran (MNHN.F.MAR3328: L = 18.0 mm, W = 6.0 mm), though still smaller than an i3 of H. antiquus from Yassiören, Turkey (MNHN.F.TRQ1026: L = 21.7 mm, W = 9.5 mm). Compared to a restricted sample (n = 6) from Pikermi, Maragheh, Dorn-Dürkheim, Germany ( Made 1997: pl. I, fig. 5) and Akkaşdağı, Turkey ( Liu et al. 2005: fig. 2B, C), the Küçükçekmece West i3 exhibits a sharp occlusal angle (i.e. the angle of the occlusal surface in buccal or lingual view) like H. antiquus from Yassiören and in difference from the smoothly convex occlusal edge of H. major , indicating a different occluding pattern of upper and lower incisors between these two species. The buccal face of the Küçükçekmece i3 also bears a weak-shallow groove similar to that of H. antiquus from Yassiören, and unlike H. major .

Apart from a single specimen from Luberon, France, the distal dp4 TQR679 ( Fig. 1C ; Pickford 2015: fig. 76B) appears 10% wider than the broadest recorded dp4 attributed to H. major (n = 24; data from Made et al. 1992; Pickford 2015). The distal part of p2 (MNHN.F.TRQ681) is wide and bears an accessory cuspid between the main conid and the high distal cusplet (or talonid). The distal cingulum is strong and extends lingually and mostly buccally. This morphology is quite different from that of H. major , in which the distal cingulum of p2 is reduced and the intermediate accessory cuspid together with the talonid raises higher. The tooth width indicates a species at the very maximum extreme end of H. major ’s size range (Wdistal <8.2 mm in 25 out of 27 cases) and within the known range for H. antiquus , though data for this species are poor (Wdistal = 9.0- 9.4 mm, n = 2 for Dinotheriensande/Eppelsheim according to Hünermann 1961; 9.2 mm for the Yassiören mandible MNHN.F.TRQ1026).

Although in advanced stage of wear, the single fully preserved third lower premolar (MNHN.F.TRQ675; Fig. 1B ; see also Pickford 2015: fig. 76D) suggests that the main conid was strong, rising much higher than the mesial or distal cusplets, a morphology that contrasts that of H. major . The distal cusplet develops both lingually and bucally, instead of mostly buccally in H. major . The p3 of H. antiquus from Eppelsheim (L = 22.3 mm, W = 11.7 mm; Hünermann 1961) bears one accessory cuspid along the anterior crest, a feature present in the Küçükçekmece p3 but not in the Yassiören mandible ( Fig. 2 ). Pickford (2015) allocates MNHN.F.TRQ675 to H. major , but using his own data (idem: table 21, fig. 77)

W p3

13

11

9

7

L 17 19 21 23

the specimen is metrically placed well within the size range of H. antiquus from Dinotheriensande, Germany together with the neighboring suid from Yulaflı, Turkey ( Geraads et al. 2005) and far from H. major from Luberon ( Fig. 2 ).

Malik & Nafiz (1933: pl. IX, fig. 2) referred to as Microstonyx erymanthius an astragalus (L = 67 mm) from the Küçükçekmece East site. This astragalus is slightly larger than those of H. major from Greece, Turkey and Spain (Made et al. 1992; Liu et al. 2005; pers. data) and it may, indeed, belong to H. antiquus , but comparative data are missing from the literature.

According to the results of the previous morphological and metrical comparison and in contrast to Pickford (2015), we suggest that the Küçükçekmece West large suid is better ascribed to Hippopotamodon antiquus than to H. major . Due, however, to the inadequate sample we prefer referring it to as Hippopotamodon cf. antiquus .

Figures

FIG. 1. — Hippopotamodon cf. antiquus from Küçükçekmece West, Turkey: A, i3 dex,MNHN.F.TRQ682 in occlusal (up) and buccal (down) views;B, p3 sin, MNHN.F.TRQ675 in occlusal (up) and lingual (down) views;C, distal part of dp4 dex, MNHN.F.TRQ679 in occlusal view; D, part of?M1 dex, MNHN.F.TRQ678 in occlusal view. Scale bar: 2 cm.

FIG. 2. — Morpho-metrical comparison of the p3s of European Hippopotamodon Lydekker, 1877: ê, MNHN.F.TRQ675, Küçükçekmece West, Turkey; H. antiquus: •, Dinotheriensande/Eppelsheim, Germany (from Hünermann 1961; Pickford 2015); ¢, Yassiören (MNHN) Turkey;, Yulaflı, Turkey. Hippopotamodon major (Gervais, 1848): D, Pikermi, Greece;, Luberon, France; °, Samos, Greece;, Dytiko, Greece;, Maragheh, Iran;, Kalimantsi, Bulgaria (pers. data).