Tarsal diversity in the earliest Eocene mammal fauna of Dormaal, Belgium
SFA – Institut International de Paléoprimatologie, Paléontologie Humaine : Evolution et Paléoenvironnements (IPHEP) – UMR CNRS 7262, Université de Poitiers, 6 rue Michel Brunet, 86022 Poitiers Cedex, France. E-mail: tiphaine.coillot@univ-poitiers.fr
Department of Paleontology, Royal Belgian Institute of Natural Sciences, Rue Vautier 29, B-1000 Brussels, Belgium. E-mail: richardsmithpal@hotmail.com
Prins Albertlei 15 bus 11, 2600 Berchem, Belgium. E-mail: paul_gigase@hotmail.com
Department of Paleontology, Royal Belgian Institute of Natural Sciences, Rue Vautier 29, B-1000 Brussels, Belgium. E-mail: thierry.smith@naturalsciences.be
Abstract
Mammal teeth bring important information regarding phylogeny and diet. However, postcranial elements, although poorly studied for small Paleogene mammals, can provide other significant data. The purpose of this study is to associate tarsal bones with dental specimens for a systematic identification. We thus chose the Belgian locality of Dormaal (Tienen Formation, Belgium) that has yielded the earliest Eocene mammals of Europe. This particularly rich fauna, dated between 55.5 and 55.8 Ma, occurred during the Paleocene-Eocene Thermal Maximum, a key period in the mammal evolution. It is composed by archaic mammals (“condylarths”, arctocyonids, plesiadapiforms, "insectivorans"…) and also by earliest modern taxa (primates, rodents, carnivoraforms, artiodactyls …), representing about 14,000 dental specimens. 488 tarsal bones are studied according to three methods: morphology, relative abundance and relative size. 12 morphotypes of astragali and 18 of calcanei are discriminated and most of them are identified at the level of species (e.g. the marsupial Peratherium constans), genus or family (e.g. Ischyromyid rodents). Biases for each method are discussed and new perspectives in phylogeny and paleoecology are proposed for further studies implying tarsal bones.