Dremotherium guthi Jehenne, 1987

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

Dremotherium guthi Jehenne, 1987

Figure 5.1-4

Referred species. D. guthi Jehenne, 1987 , D. cetinensis Ginsburg, Morales and Soria, 1994 Referred material. Bağdatlı, left m1 (BA-3); labial part of a left upper molar (BA-6).

Description and Comparisons

The lower molar (presumably an m1 because of its size, the lack of a contact surface on the base of the anterior side of the molar, and the well-marked external postprotocristid) is relatively fresh, and its enamel is wrinkled ( Figure 5.2 ). The lingual ribs of the metaconid and entoconid are barely visible (they are well-developed in D. feignouxi ), and the wall of the molar is almost flat. The posthypocristid reaches the posterior base of the entoconid where it forms a small bulge. The anteroposterior axis of the metaconid is shifted obliquely with respect to that of the entoconid; the metastylid is small. The external postprotocristid is well-marked and does not connect to the prehypocristid as in tragulids. The anterior cingulid is better developed than the posterior cingulid. The fragmentary upper molar (BA-6) is badly damaged ( Figure 5.4 ). Unlike the upper molar tentatively referred to Palaeohypsodontus ( Figure 5.5-6 ), the central fossette between the paracone and metacone is large (this feature is accentuated by the heavy wear of the molar). The styles are moderately developed and the paracone has a strong labial rib. Such a morphology is compatible with that of the upper molar figured in Jehenne (1987).

This species is known from latest Oligocene localities of Europe where it is restricted to the mammal levels MP 29 to MP 30 ( Jehenne, 1987; Scherler et al., 2013; Mennecart, 2015) while the type species D. feignouxi is restricted to the earliest Miocene (Aquitanian, MN1-2; Jehenne, 1987; Scherler et al., 2013). D. guthi is smaller than D. feignouxi , and its metastylid on the lower molars is supposedly less developed ( Jehenne, 1987). The external postprotocristid is not signaled as a diagnostic feature of this species, but we have observed such a crest on D. feignouxi and it is present but weaker on D. guthi . The genus Dremotherium has been mentioned in Europe from different MP25 localities ( Lavocat 1951; Ginsburg 1967; Hugueney 1997), but the identifications remain unsure, and such an early occurrence of the genus in Europe needs to be better documented.

In Central Asia, D. cf. guthi is reported from the upper Shand-Gol Formation at the Yagan Tologoi locality on the Dzabhan River ( Vislobokova et al., 1996), and D. cf. guthi is also reported from the Biozone C (=’Middle’ Oligocene) of the Valley of Lakes, Central Mongolia ( Vislobokova and Daxner-Höck, 2002). The age of Bağdatlı correlates with the mammal level MP27 (S. Sen pers. com.), and the occurrence of D. guthi in Central Anatolia thus predates the earliest occurrence of the species in Europe. According to Vislobokova and Daxner-Höck (2002, figure 9), their biozone C is correlative to an early late Oligocene age (MP25- 26), making the Valley of Lakes occurrence the earliest occurrence of the genus.

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.