A new Middle Miocene tarsier from Thailand and the reconstruction of its orbital morphology using a geometric-morphometric method.
Tarsius is an extant genus of primates endemic to the islands of Southeast Asia that is characterized by enormously enlarged orbits reflecting its nocturnal activity pattern. Tarsiers play a pivotal role in reconstructing primate phylogeny, because they appear to comprise, along with Anthropoidea, one of only two extant haplorhine clades. Their fossils are extremely rare. Here, we describe a new species of Tarsius from the Middle Miocene of Thailand. We reconstructed aspects of its orbital morphology using a geometric-morphometric method. The result shows that the new species of Tarsius had a very large orbit (falling within the range of variation of modern Tarsius) with a high degree of frontation and a low degree of convergence. Its relatively divergent lower premolar roots suggest a longer mesial tooth row and therefore a longer muzzle than in extant species. The new species documents a previous unknown Miocene group of Tarsius, indicating greater taxonomic diversity and morphological complexity during tarsier evolution. The current restriction of tarsiers to offshore islands in Southeast Asia appears to be a relatively recent phenomenon.
Palaeontology Section, Department of Mineral Resources, Rama VI Road, Bangkok 10400, Thailand. yaowalak@dmr.go.th
Yaowalak
Y
Chaimanee
Renaud
R
Lebrun
Chotima
C
Yamee
Jean-Jacques
JJ
Jaeger
D000818:Animals; D005075:Biological Evolution; D005580:Fossils; D007091:Image Processing, Computer-Assisted; D008437:Maxilla / Q000033:anatomy & histology; D009915:Orbit / Q000033:anatomy & histology*; D010161:Paleodontology; D010802:Phylogeny; D016699:Tarsiidae / Q000033:anatomy & histology* / Q000145:classification; D013785:Thailand; D014070:Tooth / Q000033:anatomy & histology