title: Functional morphology and anatomy of cervical vertebrae in Nacholapithecus kerioi, a middle Miocene hominoid from Kenya.
abstract: This paper describes the morphology of cervical vertebrae in Nacholapithecus kerioi, a middle Miocene primate species excavated from Nachola, Kenya in 1999-2002. The cervical vertebrae in Nacholapithecus are larger than those of Papio cynocephalus. They are more robust relative to more caudal vertebral bones. Since Nacholapithecus had large forelimbs, it is assumed that strong cervical vertebrae would have been required to resist muscle reaction forces during locomotion. On the other hand, the vertebral foramen of the lower cervical vertebrae in Nacholapithecus is almost the same size as or smaller than that of P. cynocephalus. Atlas specimens of Nacholapithecus resemble those of extant great apes with regard to the superior articular facet, and they have an anterior tubercle trait intermediate between that of extant apes and other primate species. Nacholapithecus has a relatively short and thick dens on the axis, similar to those of extant great apes and the axis body shape is intermediate between that of extant apes and other primates. Moreover, an intermediate trait between extant great apes and other primate species has been indicated with regard to the angle between the prezygapophyseal articular facets of the axis in Nacholapithecus. Although the atlas of Nacholapithecus is inferred as having a primitive morphology (i.e., possessing a lateral bridge), the shape of the atlas and axis leads to speculation that locomotion or posture in Nacholapithecus involved more orthograde behavior similar to that of extant apes, and, in so far as cervical vertebral morphology is concerned, it is thought that Nacholapithecus was incipiently specialized toward the characteristics of extant hominoids.
authors.affiliation: Division of Human Anatomy and Biological Anthropology, Department of Anatomy and Physiology, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga 849-8501, Japan. kikuchiy@cc.saga-u.ac.jp
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kikuchi
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Nakano
authors.forename: Masato
authors.initials: M
authors.lastname: Nakatsukasa
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kunimatsu
authors.forename: Daisuke
authors.initials: D
authors.lastname: Shimizu
authors.forename: Naomichi
authors.initials: N
authors.lastname: Ogihara
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tsujikawa
authors.forename: Tomo
authors.initials: T
authors.lastname: Takano
authors.forename: Hidemi
authors.initials: H
authors.lastname: Ishida
mesh_terms: D000818:Animals; D002574:Cervical Vertebrae / Q000033:anatomy & histology* / Q000502:physiology; D005260:Female; D005580:Fossils; D015186:Hominidae / Q000033:anatomy & histology* / Q000502:physiology; D007630:Kenya; D008124:Locomotion; D008297:Male; D011187:Posture