Metapterodon STROMER , 1926

Morales, Jorge & Pickford, Martin, 2017, New Hyaenodonts (Ferae, Mammalia) From The Early Miocene Of Napak (Uganda), Koru (Kenya) And Grillental (Namibia), Fossil Imprint 73 (3 - 4), pp. 332-359 : 339-340

Genus Metapterodon STROMER, 1926

1967 Pterodon Blainville, 1839 ; van Valen, p. 252.

1985 Pterodon Blainville, 1839 ; Dashzeveg, p. 234.

T y p e s p e c i e s. Metapterodon kaiseri STROMER, 1926 (with type locality: Elisabethfeld , Sperrgebiet, Namibia). Holotype is left maxillary fragment with M2 – P3 ( BSPG Nr. 1926X1).

A g e. Early Miocene.

D i a g n o s i s. Metapterodon , being the only known genus in the tribe, has the same diagnosis as the tribe.

O t h e r s p e c i e s. Metapterodon stromeri MORALES, PICKFORD et SORIA, 1998 from the Early Miocene of Langental, Sperrgebiet, Namibia.

Metapterodon aff. stromeri MORALES et al., 1998a Pl. 2, Fig. 1

L o c a l i t y. Napak V, Uganda.

A g e. Early Miocene.

M a t e r i a l. Right M2 (L = 12.8 mm, W = 12.2 mm)

(NAP V 121’08).

D e s c r i p t i o n. The occlusal outline is an obtuse isosceles triangle, in which the two equal sides are formed of the posterior surface (protocone-parastyle) and the buccal surface (parastyle-metastyle), while the unequal side is longer and extends from the paracone to the metastyle. Outstanding is the strong development of the protocone, in the shape of a pointed clog, which extends well forwards. The parastyle is strong and basally is contiguous with the moderately well-developed buccal cingulum. The paracone and metacone are largely fused together, but are slightly separated at their apices by a shallow incision on the buccal surface and are transversely compressed. The metastyle is similar in size to the paracone-metacone. The lingual cingulum is weak.

D i s c u s s i o n. The occlusal morphology and the great development of the protocone (Pl. 2, Figs 1–2) approach this molar to that of Metapterodon kaiseri STROMER, 1926 and Metapterodon stromeri MORALES et al., 1998a . It differs from the former by its greater dimensions (ca. 10%) and by the greater development of the parastyle. It differs from M. stromeri by its smaller dimensions (ca. 15%; Text-fig. 4 ).

Holroyd (1999) included three species from the Eocene-Oligocene of the Fayum, Egypt, in Metapterodon , but she raised reasonable doubts concerning the generic attribution. In particular, in the two species represented by upper dentitions (and thus comparable to the holotype of Metapterodon kaiseri ) there are important differences, noted in the descriptions by Holroyd (1999: 12, 14). According to this author, the molars of M. schlosseri and Metapterodon markgrafi are strongly modified for cutting, with a small protocone in the first species and none in the second, and in addition, the two species possess long metastyles. These differences prevent the use of Metapterodon as a possible genus for these Palaeogene forms. In contrast, as we will see later, the species could be related to Isohyaenodon , an idea indirectly supported by Savage (1965) who included in I. andrewsi one of the mandibles later identified as M. schlosseri by Holroyd (1999).

Figures

Text-fig. 4. Bivariate plots of the upper teeth (M2 – P3) of small to medium sized Miocene hyaenodonts from African localities. Data source: Pilgrim (1912, 1914, 1932), Colbert (1935), Savage (1965), Barry (1988), Morales et al. (1998a, 2007), Holroyd (1999), Rasmussen et al. (2009), Borths et al. (2016), Borths and Seiffert (2017).