Kikuchi Yasuhiro, Nakatsukasa Masato, Nakano Yoshihiko, Kunimatsu Yutaka, Shimizu Daisuke, Ogihara Naomichi, Tsujikawa Hiroshi, Takano Tomo, Ishida Hidemi
Division of Human Anatomy and Biological Anthropology, Department of Anatomy and Physiology, Faculty of Medicine, Saga University, Saga 849-8501, Japan.
Laboratory of Physical Anthropology, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
J Hum Evol. 2016 May;94:117-25. doi: 10.1016/j.jhevol.2016.03.006. Epub 2016 Apr 29.
This study describes two new sacral specimens of Nacholapithecus kerioi, KNM-BG 42753I and KNM-BG 47687A, from the Aka Aiteputh Formation in Nachola, northern Kenya, excavated in 2002. They are of roughly equal size and are considered to belong to males. When scaled by body mass, the lumbosacral articular surface area of the better preserved specimen, KNM-BG 42753I, is smaller than that in Old World monkeys but similar to that in extant great apes and New World monkeys, as well as Proconsul nyanzae. The relatively narrow dimensions of the first sacral vertebral body in the transverse and sagittal planes are characteristics of N. kerioi and P. nyanzae and similar to those of extant great apes. In N. kerioi, lumbosacral surface area relative to body mass is small. This may simply be an extension of a trend from the previously reported small thoracolumbar vertebrae to the sacrum. The first sacral vertebrae of N. kerioi and Epipliopithecus vindobonensis have a higher craniocaudal vertebral body reduction (CVR; a higher CVR indicates a wider cranial width relative to a narrower caudal width), similar to that in Old World monkeys. Old World monkeys have a higher CVR, and usually have three sacral vertebrae, fewer than seen in extant great apes, which have a lower CVR and four to six (sometimes as many as eight) sacral vertebrae. New World monkeys have a lower CVR than Old World monkeys, but generally possess only three sacral vertebrae, and have a large caudal articular surface, which may be related, at least in the Atelidae, to the grasping ability of their tails. The possibility that N. kerioi had only three sacral vertebrae cannot be ruled out, because E. vindobonensis and Old World monkeys, with higher CVRs, have sacra consisting of three sacral vertebrae.
本研究描述了两件来自肯尼亚北部纳乔拉的阿卡艾泰普特组的新的纳科拉猿骶骨标本，即KNM - BG 42753I和KNM - BG 47687A，于2002年发掘。它们大小大致相等，被认为属于雄性。按体重比例缩放后，保存较好的标本KNM - BG 42753I的腰骶关节表面积比旧世界猴小，但与现存的大猩猩、新世界猴以及尼亚萨原康修尔猿相似。纳科拉猿和尼亚萨原康修尔猿第一骶椎体在横切面和矢状面的尺寸相对较窄，这与现存大猩猩的特征相似。在纳科拉猿中，相对于体重的腰骶表面积较小。这可能仅仅是先前报道的胸椎和腰椎较小的趋势向骶骨的延伸。纳科拉猿和维也纳副猿的第一骶椎具有更高的颅尾椎体缩减率（CVR；更高的CVR表明相对于较窄的尾宽，颅宽更宽），与旧世界猴相似。旧世界猴具有更高的CVR，通常有三个骶椎，比现存大猩猩的骶椎数量少，现存大猩猩的CVR较低，有四到六个（有时多达八个）骶椎。新世界猴的CVR比旧世界猴低，但通常只有三个骶椎，并且有一个较大的尾关节面，这至少在蜘蛛猴科中可能与其尾巴的抓握能力有关。不能排除纳科拉猿只有三个骶椎的可能性，因为具有较高CVR的维也纳副猿和旧世界猴的骶骨由三个骶椎组成。
