The astragalus of Paleogene artiodactyls: comparative morphology, variability and prediction of body mass

Abstract

Martinez, J.‐N. & Sudre, 1. 1995 11 30 The astragalus of Paleogene artiodactyls: comparative morphology, variability and prediction of body mass. Lethaia, Vol. 28, pp. 197–209. Oslo. ISSN 0024–1164. The morphology of the astragalus is analysed in nineteen Paleogene artiodactyls (suborders Palaeodonta, Suina, Ancodonta and Ruminantia). This morphology is related to the functional adaptations of the appendicular skeleton, but some diagnostic characters can be seen at the family level. For the populations examined, the proportions of this bone show a low intraspecific variability, which does not allow detection of any dimorphism. An allometric relationship between the dimensions of the astragalus and the body mass has been established for extant species, allowing estimates for the fossil species. In most cases, the interval between the two extreme estimations using the astragalus includes the estimated body mass using M/1 area. The limits of this method are discussed, and it is suggested that the dimensions of the astragalus give a better estimation of the body mass than the dental area. □Artiodactyls, astragalus, comparative morphology, body mass, allometry, Paleogene.

Iberomeryx minor (Mammalia, Artiodactyla) from the Early Oligocene of Soulce (Canton Jura, NW Switzerland): systematics and palaeodiet

“…Additionally, the extant Tragulidae, Bachitherium or the Anoplotherioidea (a sister group of the Ruminantia) do not possess aligned trochleas. The aligned trochleas are a characteristic feature of the derived Ruminantia such as the Pecora (Martinez and Sudre 1995). Moreover, Iberomeryx differs from Lophiomeryx because of the astragalus articular facet with the cubo-navicular bone that does not bear a crest (Brunet and Sudre 1987;Martinez and Sudre 1995).…”

“…The aligned trochleas are a characteristic feature of the derived Ruminantia such as the Pecora (Martinez and Sudre 1995). Moreover, Iberomeryx differs from Lophiomeryx because of the astragalus articular facet with the cubo-navicular bone that does not bear a crest (Brunet and Sudre 1987;Martinez and Sudre 1995). The metatarsal bones of Lophiomeryx are not fused (Geraads et al 1987;Blondel 1997) and, on the upper molars, the metacone and paracone are aligned contrary to Bachitherium (Ferrandini et al 2000) and the Tragulidae.…”

“…These doubtful specimens are in need of revision, as the dental structure of primitive ruminants is very similar and can easily be confused. According to Geraads et al (1987) and Martinez and Sudre (1995), only the combination of the astragalus shape, the diastema length, the mandible robustness, the p4 structure, and the lower molar shape permit to differentiate between them. In fact, their reassessment could ascribe them to small Gelocidae or Bachitherium vireti from the Early Oligocene.…”

Oligocene ruminants from the Kızılırmak Formation, Çankırı-Çorum Basin, Central Anatolia, Turkey

“…The used postcranial terminology is mesio/distal, media/lateral, and plantar/ dorsal. The body mass estimations provided from the size of the astragalus follow the method proposed in Martinez and Sudre (1995). The estimated body mass of I. parvus from Benara was obtained by using the m1 area (Wm1) of the type specimen (Gabunia, 1964, p. 182) and the method of Legendre (1989).…”

“…The largest astragalus and cubonavicular (Figure 4.4-6) are about twice the size of the smallest astragalus and cubonavicular in our sample (Figure 4.1-3). The estimates of body mass provided from the size of the astragalus (Martinez and Sudre, 1995) show that such a variation would not fit the size variation of Tragulus kanchil, the smallest extant tragulid (Table 3). Strikingly, this variation of size is not reflected in the dental material which is associated with the medium-and large-sized tarsal elements of our sample.…”