Palaeohypsodontus, Trofimov, 1958

Métais, G, Albayrak, E, Antoine, P, Erdal, O, Karadenizli, L, Oyal, N, Saraç, G, İslamoğlu, Y & Sen, S, 2016, Oligocene ruminants from the Kızılırmak Formation, Çankırı-Çorum Basin, Central Anatolia, Turkey, Palaeontologia Electronica 19 (3), pp. 1-23 : 14-16

Genus PALAEOHYPSODONTUS Trofimov, 1958

Type species. P. asiaticus Trofimov, 1958

cf. Palaeohypsodontus sp.

Figure 5.5-6

Referred species. P. zinensis Métais et al., 2003 ; P. sp. (cited in Vislobokova and Daxner-Höck, 2002).

Referred material. TP641-10, lingual part of upper molar.

Description and Comparisons

We have tentatively identified this genus on the basis of one fragmentary upper molar (the labial wall is lacking, Figure 5.5 ) from the locality Tepe 641. The protocone and metaconule are subequal in size, and highly crescent shaped and fully connected to the labial lobes. The crest resulting from the fusion of postprotocristid and the premetaconule-cristid plugs the central fossette of the molar. These crests are generally not fused in traguloids and Dremotherium even on highly worn molars. The tooth is moderately worn, and it is reasonable to suppose that the unworn teeth of the animal were high-crowned. The enamel is slightly wrinkled ( Figure 5.6 ).

Although very fragmentary, this unique molar is highly reminiscent of that of the enigmatic genus Palaeohypsodontus Trofimov 1958 , known from Oligocene deposits of Central Asia ( Trofimov, 1958; Flerov, 1971; Dmitrieva, 2002), Mongolia ( Vislobokova and Daxner-Höck, 2002), China ( Huang, 1982, 1985), and Pakistan ( Métais et al., 2003; Barry et al., 2005). It is worth noting that this taxon is mostly based on lower dentitions. However, Huang (1985) described upper molars that are tentatively referred to Palaeohypsodontus in regard to the “high-crowned” morphology of the material. Barry et al., (2005) also reported the lingual half of an upper molar without figuring it. We cannot determine the rank of the molar TP641-8 on the maxilla but it is an appropriate size for P. zinensis from the late Oligocene lower Chitarwata Formation in the Bugti Hills, Pakistan ( Métais et al. 2003), and to a lesser degree for the material from Ulan Tatal (Oligocene, China) referred to Palaeohypsodontus cf. asiaticus by Huang (1985). However, given the scarcity of the present material, we prefer to be cautious and to leave it as cf. Palaeohypsodontus sp. According to Barry et al. (2005), P. zinensis is also present in the lower Vihowa Formation in the Zinda Pir, which would represent the youngest occurrence of the species with an age of ca. 18.5 Ma ( Lindsay et al., 2005; Antoine et al., 2013). The familial affinities and origin of this mesodont ruminant remains a tricky issue, because of its unexpected bovid-like dental morphology and the quasi absence of post-cranial information. Despite its antiquity, several authors have included this form within bovids although there is currently no evidence of cranial appendages in Palaeohypsodontus .

Figures

FIGURE 5. Dremotherium guthi: 1-3, Left m1 in occlusal (1), labial (2), and lingual (3) views, BA-1; 4, M2? In occlusal view, BA-6; cf. Palaeohypsodontus sp.: 5-6, Right M2? in occlusal (5) and lingual (6) views, TP641-10; Lophiomerycidae indet.: 7, Right calcaneum in medial view, GK2-7; 8, Right p1 in labial view, TP641-9; 9, Right cubonavicular in anterior view, GK2-3. Large Pecora indet.: 10-11, Right astragalus in anterior (10) and posterior (11) views, KZ-9. Anatomical abbreviations: cf, calcaneal facet; fbf, fibular facet; stf, sustentacular facet. The scale bar 10 mm goes exclusively with the views 7 to 11.

FIGURE 6. Stratigraphic ranges of late Eocene to Oligocene ruminant species in Eurasia (adapted from Métais and Vislobokova, 2007); the Land Mammal Ages are based on Tong et al. (1995), and Woodburne (2006). The colored area designates the duration of the late Oligocene Warming according to the chart of Zachos et al. (2001).