Sectisodon occultus, Morales & Pickford, 2017

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 : 346

Sectisodon occultus sp. nov.

Pl. 4

2007 Isohyaenodon zadoki ( Savage, 1965) ; Morales et al., pp. 72–74.

H o l o t y p e. Right M2 (UM NAP V 178’08).

T y p e l o c a l i t y. Napak V, Uganda.

A g e. Early Miocene.

O t h e r l o c a l i t i e s. Napak I and Napak IV, Uganda .

D e s c r i p t i o n.NAPIV72’04, right P3 (L = 7.75 mm, W = 5.46 mm, H paracone = 7.01 mm). This is a narrow premolar with the main cusp tall and sharp. There is a small posterior cusplet and a well-marked basal cingulum completely encircling the tooth. The protocone is reduced to a lingual bulge in the middle of the tooth joined to the cingulum and quite a bit deeper than the base of the main cusp. The morphology is analogous to that seen in the protocones of the molars.

NAP IV 01’09, right M1 (L = 8.1 mm, W = 5.58 mm, H. paracone = 6.19 mm, mestastyle length = 3.63 mm). Short molar with tall cusps. Paracone and metastyle of similar size. The protocone is greatly reduced, flattened and extending low down beyond the base of the paracone. Reduced parastyle included in the anterior cingulum. Basal cingula almost imperceptible. The molar has a vertical wear facet on the lingual surface of the paracone and the metastyle (Pl. 4, Fig. 2a).

NAP V 178’08, right M2 (L = 8.57 mm, W = 4.32 mm, H paracone = 5.52 mm, Mestastyle length = 3.85 mm). This specimen is morphologically similar to the preceding one, similar in length, but narrower and with lower cusps. The parastyle and protocone seem to be quite big and the metastyle elongated. There is a small interstitial facet at the posterior part of the base of the metastyle (Pl. 4, Fig. 3a) probably produced by contact with a small M3.

D i s c u s s i o n. Sectisodon represents a more advanced sectorial adaptation than other hyaenodonts from the Miocene of Africa, with the exception of Exiguodon . The upper molars (M1 – M2) almost lack protocones, which differentiates them from those of Metapterodon , in which the M2 has a hyperdeveloped protocone. With respect to Exiguodon described in this work, apart from the reduction of the protocone in the upper molars, the morphological differences are important, in particular the strong development of the cingulum and the buccal platform that occurs in this genus.