title: The face of Siamopithecus: new geometric-morphometric evidence for its anthropoid status.
abstract: Amphipithecids assume a key position in early primate evolution in Asia. Here we report on new maxillofacial and associated mandibular remains of Siamopithecus eocaenus, an amphipithecid primate from the Late Eocene of Krabi (Thailand) that currently represents the most complete specimen belonging to this group. We used synchrotron microtomography and techniques of virtual reconstruction to recover the three-dimensional morphology of the specimen. Geometric-morphometric analysis of the reconstructed specimen within a comparative sample of recent and fossil primates clearly associates Siamopithecus with the anthropoids. Like modern anthropoids, Siamopithecus displays a relatively short face and highly convergent and frontated orbits, the lower rim of which lies well above the alveolar plane. The cooccurrence of spatially correlated anthropoid features and classical anthropoid dental characters in one individual represents a strong argument to support the anthropoid status of Siamopithecus. It is, thus, highly unlikely that amphipithecids are specialized adapiforms exhibiting complete convergence with anthropoids.
authors.affiliation: Anthropological Institute, University of Zürich, Zürich, Switzerland. zolli@aim.uzh.ch
authors.forename: Christoph P E
authors.initials: CP
authors.lastname: Zollikofer
authors.forename: Marcia S
authors.initials: MS
authors.lastname: Ponce De León
authors.forename: Yaowalak
authors.initials: Y
authors.lastname: Chaimanee
authors.forename: Renaud
authors.initials: R
authors.lastname: Lebrun
authors.forename: Paul
authors.initials: P
authors.lastname: Tafforeau
authors.forename: Sasidhorn
authors.initials: S
authors.lastname: Khansubhaand
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Jaeger
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D000885:Anthropology, Physical / Q000379:methods; D005075:Biological Evolution; D002508:Cephalometry / Q000379:methods; D005147:Facial Bones / Q000033:anatomy & histology* / Q000502:physiology; D005247:Feeding Behavior / Q000502:physiology; D000882:Haplorhini / Q000033:anatomy & histology* / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods; D007568:Jaw / Q000033:anatomy & histology / Q000502:physiology; D010163:Paleontology / Q000379:methods; D010802:Phylogeny; D011323:Primates / Q000033:anatomy & histology* / Q000502:physiology; D012886:Skull / Q000033:anatomy & histology* / Q000502:physiology; D013045:Species Specificity; D013785:Thailand; D014070:Tooth / Q000033:anatomy & histology / Q000502:physiology