著者

TOMO TAKANO MASATO NAKATSUKASA MARTA PINA YUTAKA KUNIMATSU YOSHIHIKO NAKANO NAOKI MORIMOTO NAOMICHI OGIHARA HIDEMI ISHIDA

出版者

The Anthropological Society of Nippon

雑誌

Anthropological Science (ISSN:09187960)

巻号頁・発行日

pp.200116, (Released:2020-03-17)

被引用文献数

5

---

This article reports eight new humeral, ulnar, and radial fragments of Nacholapithecus kerioi collected from Nachola, Kenya during the 1998/1999 field seasons. The study refines the description of its forelimb bones, which was mostly based on a single partial skeleton. The most distinctive feature of the distal humerus is a large, globular, medially tilted capitulum. The groove between the capitulum and the zona conoidea is quite deep. The medial part of the humeral trochlea is also diagnostic in showing a less salient medial border. The medial epicondyle is moderately long and more posteriorly reflected than was previously presumed. The coronoid process of the ulna is quite wide. Its medial portion is distinctly concave. The ulnar shaft is anteroposteriorly deep in its proximal half, slender, straight in frontal view, and weakly anteriorly bowing. The elbow of Nacholapithecus exhibits a primitive functional pattern as a hominoid, including lack of universal stability of the humeroulnar joint through full extension and flexion, restriction of hyperextension of the elbow, and relatively anteroposteriorly oriented loading at the proximal ulna. On the other hand, it is derived in terms of enhanced rotational mobility and stability of the radius, incipiently increased stability at the humeroulnar joint, and more frequent maximum extension of the elbow compared to proconsulids. This mosaic morphology is different from both early Miocene proconsulids and later suspensory or orthograde European fossil apes. Although Nacholapithecus was neither suspensory nor orthograde, its forelimbs may have played a greater role for body support or balance maintenance, more frequently reaching to and exploiting overhead supports than in early Miocene proconsulids.

著者

TOMO TAKANO MASATO NAKATSUKASA YUTAKA KUNIMATSU YOSHIHIKO NAKANO NAOMICHI OGIHARA HIDEMI ISHIDA

出版者

The Anthropological Society of Nippon

雑誌

Anthropological Science (ISSN:09187960)

巻号頁・発行日

vol.126, no.3, pp.135-149, 2018 (Released:2018-12-21)

参考文献数

59

被引用文献数

10

---

This paper provides a thorough description of humeral, ulnar, and radial specimens of the Nacholapithecus holotype (KNM-BG 35250). A spool-shaped humeral trochlea (and keeled sigmoid notch of the ulna) is a hallmark of elbow joint evolution in hominoids. In lacking this feature, the elbow of Nacholapithecus is comparatively primitive, resembling that of proconsulids. However, the humeroulnar joint in Nacholapithecus is specialized for higher stability than that in proconsulids. The humeroradial joint (humeral capitulum) resembles that of extant apes and Sivapithecus. This condition may represent an intermediate stage leading to the fully modern elbow in extant apes. If this is the case, specialization of the humeroradial joint preceded that of the humeroulnar joint. Nacholapithecus elbow joint morphology suggests more enhanced forearm rotation compared to proconsulids. This observation accords with the forelimb-dominated positional behavior of Nacholapithecus relative to proconsulids, which has been proposed on the grounds of limb proportions and the morphology of the phalanges, shoulder girdle, and vertebrae.

著者

YUTAKA KUNIMATSU HIROSHI TSUJIKAWA MASATO NAKATSUKASA DAISUKE SHIMIZU NAOMICHI OGIHARA YASUHIRO KIKUCHI YOSHIHIKO NAKANO TOMO TAKANO NAOKI MORIMOTO HIDEMI ISHIDA

出版者

The Anthropological Society of Nippon

雑誌

Anthropological Science (ISSN:09187960)

巻号頁・発行日

vol.125, no.2, pp.59-65, 2017 (Released:2017-09-21)

参考文献数

52

被引用文献数

2

---

We here describe a prosimian specimen discovered from the early Middle Miocene (~15 Ma) of Nachola, northern Kenya. It is a right maxilla that preserves P4–M3, and is assigned to a new species of the Miocene lorisid genus Mioeuoticus. Previously, Mioeuoticus was known from the Early Miocene of East Africa. The Nachola specimen is therefore the first discovery of this genus from the Middle Miocene. The presence of a new lorisid species in the Nachola fauna indicates a forested paleoenvironment for this locality, consistent with previously known evidence including the abundance of large-bodied hominoid fossils (Nacholapithecus kerioi), the dominance of browsers among the herbivore fauna, and the presence of plenty of petrified wood.