Nakatsukasa Masato, Kunimatsu Yutaka, Nakano Yoshihiko, Takano Tomo, Ishida Hidemi
Laboratory of Physical Anthropology, Kyoto University, Sakyo, Kyoto 606-8502, Japan.
Primates. 2003 Oct;44(4):371-412. doi: 10.1007/s10329-003-0051-y. Epub 2003 Sep 24.
We describe phalanges of the KNM-BG 35250 Nacholapithecus kerioi skeleton from the Middle Miocene of Kenya. Phalanges of N. kerioi display similarities to those of Proconsul heseloni despite their enhanced robusticity. They do not show highly specialized features as in living suspensory primates. However, N. kerioi manifests several distinctive features that are observed in neither living arboreal quadrupeds nor P. heseloni or P. nyanzae. The most remarkable of them is its phalangeal elongation. N. kerioi phalanges (particularly pedal) are as long as those of Pan despite its much smaller body size. While lengthened digits enable a secure grip of supports and are especially adaptive for grasping large vertical trunks, the skeletal and soft tissues are subjected to greater stress. Probably, strong selective pressures favored powerful hallucal/pollical assisted grips. Although this functional adaptation does not exclude the possible use of the terrestrial environment, arboreal behavioral modes must have been crucial in its positional repertoire. N. kerioi is distinguished from P. heseloni in the greater size of its manual phalanges over its pedal phalanges. These derived features of N. kerioi suggest positional modes supporting more weight on the forelimb, and which occur more frequently on vertical supports. If Proconsul is referred to as an "above-branch arboreal quadruped" with a deliberate and effective climbing capability, N. kerioi may be thought of as an "orthograde climber". While living apes are powerful orthograde climbers, they are also more or less suspensory specialists. Suspensory behavior (plus climbing) and pronograde quadrupedalism (plus climbing) are the two main arboreal behavioral adaptations in living anthropoids. Thus, N. kerioi is an unusual fossil primate in that it cannot be incorporated into this dichotomy. It is plausible that a N. kerioi-like orthograde climber with large forelimbs and cheiridia was a precursor of suspensory living apes, and N. kerioi may demonstrate what an initial hominoid of this grade might have looked like.
我们描述了来自肯尼亚中新世中期的KNM - BG 35250纳科尔古猿（Nacholapithecus kerioi）骨骼的指骨。尽管纳科尔古猿的指骨粗壮程度有所增强，但仍与赫氏原康修尔猿（Proconsul heseloni）的指骨有相似之处。它们不像现存的悬垂类灵长动物那样具有高度特化的特征。然而，纳科尔古猿表现出一些在现存树栖四足动物、赫氏原康修尔猿或尼安萨原康修尔猿（P. nyanzae）中都未观察到的独特特征。其中最显著的是其指骨的伸长。纳科尔古猿的指骨（尤其是足部的）与黑猩猩（Pan）的指骨一样长，尽管它的体型要小得多。虽然加长的手指能更牢固地抓住支撑物，尤其适合抓握粗大的垂直树干，但骨骼和软组织会承受更大的压力。可能强大的选择压力有利于有力的拇趾/拇指辅助抓握。尽管这种功能适应并不排除可能利用陆地环境，但树栖行为模式在其姿势技能中肯定至关重要。纳科尔古猿与赫氏原康修尔猿的区别在于其手部指骨比足部指骨更大。纳科尔古猿的这些衍生特征表明其姿势模式是前肢承担更多重量，且这种情况在垂直支撑物上更频繁发生。如果将原康修尔猿称为具有深思熟虑且有效的攀爬能力的“树枝上方树栖四足动物”，那么纳科尔古猿可能被视为“直立攀爬者”。现存的猿类是强大的直立攀爬者，但它们或多或少也是悬垂专家。悬垂行为（加上攀爬）和前肢前伸的四足行走（加上攀爬）是现存类人猿的两种主要树栖行为适应方式。因此，纳科尔古猿是一种不寻常的化石灵长类动物，因为它不能被纳入这种二分法。有可能具有大型前肢和掌骨的类似纳科尔古猿的直立攀爬者是悬垂类现存猿类的前身，而纳科尔古猿可能展示了这个等级的原始类人猿可能的样子。
