Canthumeryx sirtensis Hamilton, 1973

Rios, M, Danowitz, M & Solounias, N, 2016, First comprehensive morphological analysis on the metapodials of Giraffidae, Palaeontologia Electronica 410 (10453), pp. 1-39 : 12

Canthumeryx sirtensis Hamilton, 1973

Specimen. KNM-MO 41

Description. The medial and lateral epicondyles are asymmetrical in size and morphology. The medial epicondyle is large with a rectangular and flat surface. The lateral epicondyle is more confined, is triangular-shaped, and is more protruding proximally ( Figure 14.1 ). There is a wide deep groove between the lateral aspect of the lateral epicondyle and the shaft, separating it into two distinct heads that flare outward. There is wide, deep groove between the medial aspect of the medial epicondyle and the shaft, separating it into two distinct heads that strongly flare outward, notably on the dorsal head ( Figure 16 ). The pygmaios is pointed, protrudes proximally, and is oriented longitudinally. It has a stronger connection with the medial epicondyle. There is a fossa in the proximal plantar surface with a sharp medial wall and a rounded lateral wall. The medial and lateral ridges are broad and flat, creating a very narrow, intermediate in depth central groove ( Figure 17). The lateral ridge is more rounded than the medial ridge.

Figures

FIGURE 14. Palmar views of the right metacarpals (left) and plantar views of the metatarsals (right) of certain Giraffidae. 1, Canthumeryx sirtensis, early-middle Miocene, Moruorot Hill, NMK Mo 41 (metatarsal); 2, Bohlinia attica, late Miocene, Pikermi, MNHNP 27561 (metacarpal), MNHNP 2357 (metatarsal) (reversed); 3, Giraffa camelopardalis, Zaire, AMNH 53550 (metacarpal), AMNH 53550 (metatarsal) (both reversed). Scale bar equals 200 mm.

FIGURE 16. Three selected metatarsal characteristics. This simplified table can be used to facilitate specimen identifications and differentiate between different giraffid taxa.