Decennatherium pachecoi Crusafont, 1952

Rios, M, Danowitz, M & Solounias, N, 2016, First comprehensive morphological analysis on the metapodials of Giraffidae, Palaeontologia Electronica 410 (10453), pp. 1-39 : 16

Decennatherium pachecoi Crusafont, 1952

Specimens. MNCN 42765, MNCN 42768, MNCN 42764, MNCN 42767, MNCN 42766, MNCN 42778, MNCN 42770

Description. The proximal articular surface exhibits three distinct facets: the facet for the os naviculocuboideum (lateral) is kidney-shaped, and the facet for the os cuneiforme intermediolaterale (medial) is half-moon shaped. The os cuneiforme mediale facet is oval and touches the os cuneiforme intermediolaterale facet in one point ( Figure 18.3 ). On the lateral facet, there is a distinct constriction where the lateral ridge meets the lateral epicondyle. The medial and lateral epicondyles are asymmetrical in size, the medial being more prominent ( Figure 5.4 ). The medial epicondyle is separated into a plantar and a dorsal head by a longitudinal groove that continues down the medial aspect of the shaft. Both heads slightly flare outward. The lateral epicondyle is separated into a dorsal and plantar head by a notably deep, wide groove. The plantar head is oriented longitudinally and the dorsal head flares outward. The pygmaios presents as a distinct, oval protrusion with a rounded surface, which is oriented medially and protrudes proximally ( Figure 16 ). There is a bony protrusion on the medial surface of the medial epicondyle. The medial and lateral ridges originate at the distal aspect of the plantar heads of the medial and lateral epicondyles. There is a deep groove that separates the medial and lateral epicondyles, which continues onto the central trough. The medial and lateral ridges continue to just proximal to the distal condyles, where they abruptly flatten. The central trough is intermediate to shallow in depth ( Figure 17) and flattens at the distal aspect of the shaft. The medial ridge is rounder than the lateral ridge. The distal shaft flares laterally. The keels of the distal condyle continue slightly onto the plantar shaft.

Figures

FIGURE 5. Palmar views of the right metacarpals (left) and plantar views of metatarsals (right) of certain Giraffidae. 1, Helladotherium duvernoyi, late Miocene, Pikermi, NHM 11382 (metacarpal), MNHNP 1554 (metatarsal) (both reversed); 2, Bramatherium megacephalum, late Miocene-Pliocene, Siwaliks, AMNH 29820, (metacarpal), AMNH 19668 (metatarsal); 3, Sivatherium giganteum, Pleistocene, Siwaliks, NHM 39553 (metacarpal), NHM 39752 (metatarsal); 4, Decennatherium pachecoi, late Miocene, Los Valles de la Fuentidueña, MNCN 42769 (metacarpal), MNCN 42764 (metatarsal) (both reversed); 5, Birgerbohlinia schaubi, late Miocene, Piera, IPS 5060 (metacarpal), Crusafont, 1952, fig. 15-5 (metatarsal), (both reversed); 6, Okapia johnstoni, Zaire, AMNH 51196 (metacarpal), AMNH 51196 (metatarsal). 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.

FIGURE 18. Metatarsal proximal morphology. 1, Helladotherium duvernoyi, late Miocene, Pikermi, M 1138; 2, Bramatherium megacephalum, late Miocene-Pliocene, Siwaliks, AMNH 19688; 3, Decennatherium pachecoi, late Miocene, Los Valles de Fuentidueña, MNCN 42764; 4, Birgerbohlinia schaubi, late Miocene, Piera, IPS 5090. Abbreviations: NC, os naviculocuboideum facet; CIL, os cuneiforme intermediolaterale facet; CM, os cuneiforme mediale facet. Images not to scale.