Computed tomography examination of the face of
Macaca anderssoni (Early Pleistocene, Henan, northern China): implications for the biogeographic history of Asian macaques伊藤毅，西村剛，Ebbestad JOR，高井正成 M. anderssoniは，前期更新世（約260～80万年前）の中国北部に分布したマカクの化石種である．M. anderssoniは，ニホンザル等を含むカニクイザル種群に近縁であると考えられることもあったが，チベットモンキー等を含むトクザル種群に近縁であるとする仮説もあり，その系統的位置に関する議論は混乱していた．我々は，形質の相同性を攪乱するアロメトリー（サイズに依存した形の変化）の影響を考慮し，かつ従来調べられていなかった顔面頭蓋内部（鼻腔や上顎洞）の形質を用いることで，M. anderssoniの系統的位置を検討した．結果，顔面の表面形態における種群間の系統的差違を検出することに成功したが，M. anderssoniはその変異においていずれの系統群にも属さず，中間形を示した．一方，M. anderssoniの鼻腔の形質は，現生のトクザル種群の一部のみにみられる特徴を示した．M. anderssoniの顔面の表面形態は祖先的と考えられ，いずれの系統群とも近縁性を示さないが，鼻腔の形質の一部は派生的と考えられ，トクザル種群との近縁性を示唆している．ただし，この推定結果は，M. anderssoni がカニクイザル種群に属するという可能性を排除するほどの統計的支持を得なかった．したがってM. anderssoniの系統的位置は決定的ではないが，本研究の推定結果が正しいとすれば，トクザル種群（に近縁な祖先系統）は前期更新世には中国北部にまで分布域を広げていたことになる．おそらく後期更新世の寒冷化と乾燥化によって，同種群は分布域を縮小させたと考えられるが，中期更新世以降に北上して来たと考えられるカニクイザル種群は分布域の縮小を免れた．カニクイザル種群は，トクザル種群に比べて環境変化に耐えるための何らかの生物学的利点をもつのかもしれない． Journal of Human Evolution 72: 64-80 Macaca
anderssoni, a fossil macaque from the Early Pleistocene of northern China, has attracted much
attention from researchers in terms of reconstructing the biogeographic history of Asian macaques, while
its phylogenetic position remains debatable. In the present study, we evaluated patterns of variation in
external and internal craniofacial morphologies among four phylogenetic groups of extant macaques (the
fascicularis, sinica, silenus, and sylvanus groups), using computed tomography and multivariate analyses.
We also reassessed the holotype of M. anderssoni, a partial cranium preserving the face and palate, to
evaluate the phylogenetic group to which M. anderssoni is most closely related. Facial elongation was
found to be significantly influenced by size. The particular combination of some allometric and nonallometric
shape components was found to reflect phylogenetic relationships; however, these features
of M. anderssoni fall intermediate among the four phylogenetic groups, with no typical similarities to any
one group. The variations in nasal cavity shape were found to reflect phylogenetic relationships but those
of the maxillary sinus did not. Macaca anderssoni has a nasal cavity that is laterally expanded anteriorly
and constricted posteriorly, a unique morphology among macaques and shared only with larger members
of the sinica group. This unique feature is considered to be a derived condition among macaques,
suggesting that M. anderssoni is phylogenetically related to the sinica group (especially
M. assamensis,
M. thibetana, and M. arctoides) and that the populations of the sinica group were distributed in northern
China during the Early Pleistocene. Currently, the populations of the sinica group are not distributed in
northern East Asia, while those of the fascicularis group are. Thus, probably due to climatic deterioration
in the Late Pleistocene, the former lineage has retreated southward or has become extinct in this region,
being replaced by the latter lineage. JUN/27/2014
Copyright(C) 2014 PRI ( ).
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