title: New strepsirrhine primate from the late Eocene of Peninsular Thailand (Krabi Basin).
abstract: In this paper, we describe the newly discovered lower jaw of a primate from the late Eocene Krabi coal mine (Bang Mark pit) of Peninsular Thailand. We performed microtomographic examinations at the European Synchrotron Radiation Facility (ESRF, Grenoble, France) to analyze different morphological aspects of the jaw and teeth. Although partially preserved, this fossil mandible reveals a set of distinctive dental traits (e.g., double-rooted P(2) and molarized P(4)) that allow us to describe a new stepsirrhine adapiform: Muangthanhinius siami, new genus and species. This taxon is somewhat atypical among Paleogene adapiforms, and more specialized than the sivaladapid adapiforms (hoanghoniines) that existed in Asia in the same epoch. In fact, Muangthanhinius shows a degree of dental specialization approximating that of some modern strepsirrhine lemuriforms, although it lacks the highly specialized anterior dentition characterizing this living primate group (canine + incisors forming a very procumbent toothcomb). In contrast, Muangthanhinius exhibits a large canine deeply anchored within the dentary that probably protruded high above the toothrow. Finally, despite the development of a molarized P(4) as in Miocene sivaladapid sivaladapines, Muangthanhinius differs in molar morphology from this group, and the position of this new taxon within the Adapiformes remains indeterminate. Clarification of its phylogenetic position will require more morphological evidence than is currently available.
authors.affiliation: Laboratoire de Paléontologie, Institut des Sciences de l'Evolution de Montpellier (ISE-M, UMR-CNRS 5554), Université de Montpellier II, F-34095 Montpellier, France. marivaux@isem.univ-montp2.fr
authors.forename: Laurent
authors.initials: L
authors.lastname: Marivaux
authors.forename: Yaowalak
authors.initials: Y
authors.lastname: Chaimanee
authors.forename: Paul
authors.initials: P
authors.lastname: Tafforeau
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Jaeger
mesh_terms: D000818:Animals; D005580:Fossils; D049690:History, Ancient; D008334:Mandible / Q000033:anatomy & histology*; D011443:Strepsirhini / Q000033:anatomy & histology*; D013785:Thailand; D014070:Tooth / Q000033:anatomy & histology*