Ronzotherium sp.

Antoine, Pierre-Olivier & Sen, Sevket, 2016, Rhinocerotidae and Chalicotheriidae (Perissodactyla, Tapiromorpha), Geodiversitas 38 (2), pp. 245-259 : 247-248

Ronzotherium sp.

( Fig. 1 A-D)

MATERIAL. — MNHN.F.TRQ355, left m1-2.

DESCRIPTION

This large tooth is eroded, with a grey patina distinct from that of other studied specimens, and partly covered by recent marine organisms, such as serpulids, barnacles, and micromollusks. There is a wear facet due to a posterior tooth (m2 or m3; Fig. 1D ), so it can be identified as an m1 or m2. The occlusal outline is rectangular ( Fig. 1A ). The crown is very low and bulbous with thick transverse lophids. The width/ length ratio is high (0.65). The paralophid is thin and low. Enamel is thinly crenulated and corrugated. The anterior cingulid is smooth but located high and horizontal. The labial cingulid is restricted to an oblique ridge at the bottom of the ectolophid groove ( Fig. 1C ). The anterior and posterior lingual valleys are closed by a crenulated ridge resembling a lingual cingulid (but not homologous with it). The posterior cingulid is continuous and sigmoid, with its lingual tip forming a spur pointed upward. Lingual cuspids are not constricted. The lingual side of the hypoconid is flat, vertical and straight. The talonid is very low with respect to the trigonid. The bottom of the posterior valley is rounded but V-shaped ( Fig. 1B ) in lingual view.

DISCUSSION

As indicated by its grey patina and eroded aspect, this tooth is at odds with other tapiromorph remains from Küçükçekmece (quartz-rich red sands). Moreover, together with the large size of this tooth, most morphological features (rectangular outline, low and bulbous crown, high width/length ratio, shape and location of the cingulid, paralophid and hypolophid low, lophids transverse, lingual side of the hypoconid flat and straight) concur to point to the early diverging rhinocerotid Ronzotherium ( Beliajeva 1954; Dashzeveg 1991; Antoine et al. 2003a; Ménouret & Guérin 2009). Representatives of this genus are commonly occurring in late Eocene-Oligocene localities of Eurasia, and more specifically in Oligocene deposits of Europe ( Brunet 1979; Uhlig 1999; Becker 2009; Ménouret & Guérin 2009). Oligocene sedimentary deposits are mapped in the vicinity of Küçükçekmece West, and MNHN.F.TRQ355 likely originates from these levels. However, it is impossible to locate the exact provenance of this outlier specimen, as being a: i) reworked specimen amalgamated in upper Miocene sands or, more likely; and ii) a specimen recently extracted from Oligocene deposits by natural erosion, mixed up with upper Miocene deposits cropping out, and then surface-collected.

Subfamily RHINOCEROTINAE Gray, 1821 Tribe RHINOCEROTINI Gray, 1821

Figures

FIG. 1. — Tapiromorph perissodactyls from the upper Miocene locality of Küçükçekmece, Thrace, Turkey: A-D, Ronzotherium sp. (reworked); MNHN.F.TRQ355, left m1 or m2 in occlusal (A), lingual (B), labial (C), and posterior views (D); E-M, Ceratotherium neumayri; E, TRQ343, right M1 in occlusal view; F-G, TRQ360, right radius in proximal (F) and anterior views (G); H-J, TRQ327, right Mc2, in anterior (H), proximal (I), and distal views (J); K-M, TRQ333, right calcaneus, in distal (K), anteroproximal (L), and medial views (M). Scale bar: A-E, 20 mm; F-M, 30 mm.