シロテテナガザル(<i>Hylobates lar</i>)の犬歯形態と性的二型  [in Japanese] Canine crown morphology and sexual dimorphism in the <i>Hylobates </i><i>lar </i>  [in Japanese]

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Author(s)

Abstract

小型類人猿シロテテナガザル(<i>Hylobates lar</i>)について犬歯形態の詳細な記載と大きさの性的二型性を明らかにすることを目的に研究を行った。テナガザルの犬歯は従来いわれているように性的二型性が小さく,雌雄間で形態が非常によく似ている。歯冠頬側面の概形は上顎犬歯でサーベル形,下顎犬歯は不正四辺形を呈する。オスに較べてメスの形態特徴を挙げると,1)サイズが小さい,2)歯冠浮彫像の発達が弱く,全体に丸みを帯びている,3)下顎犬歯の近心shoulderの位置が歯冠高の約1/2にある,4)歯頚隆線がよく発達していることである。歯冠サイズによる犬歯の性差では,上・下顎の歯冠基底部のサイズや歯冠高でオスの方が有意に大きい。一方,下顎犬歯では歯冠近遠心径に対する歯頚部エナメル質の膨らみはメスの方が大きく,有意に強い性差を示す。歯冠の高径,とくに下顎犬歯の尖頭から近心shoulderまでの距離が最も強い性差を示す。犬歯の形態やサイズに性的二型がみられることはペア社会を構成するテナガザルでもある程度雌雄の違いが大きさや形にも存在することを示す。

We aimed to describe crown morphology and sexual dimorphism of the canine in the <i>Hylobates lar</i>. As have been reported in the previous studies, the canines of male and female <i>Hylobates lar</i> were nearly the same in morphology as well as in size. Viewed from the buccal aspect, the contours of maxillary canines of both sexes had a saber-like form, while those of the mandibular canines had a quadrilateral form. However, the results in the present study indicated that sexual dimorphism in the canines of <i>Hylobates lar</i> was slightly but definitely found, not only in the size but also in the shape and structure of the canine teeth. Compared with the male canines, the female canines were characterized as follows: 1) smaller in whole size, 2) the crown reliefs, such as grooves and ridges, were less developed, which gave blunt and roundish appearance, 3) the mesial shoulder of mandibular canine was located relatively higher toward the cusp tip, 4) the cervical ridge was more developed. Odontmetrically, male canines were significantly larger in the basal crown size and higher in crown height. Crown heights in upper and lower jaws, especially the distance from the cusp tip to the mesial shoulder were also greater in males than females. On the other hand, the enamel bulge of cervical portion relative to maximum diameter of the mandibular canine crown was significantly stronger in female. Moreover, the mesial shoulder in female located as high as middle of the crown height; the average relative distance between mesial shoulder and cervical line in male was 32.8% of the crown height, while 48.1% in female. The degree of canine sexual dimorphism in <i>Hylobates</i> suggests that sexual differences are present even in the paired-social group, which may suggest male male competition in <i>Hylobates lar</i>.

Journal

  • Anthropological Science (Japanese Series)

    Anthropological Science (Japanese Series) 122(2), 133-143, 2014

    The Anthropological Society of Nippon

Codes

  • NII Article ID (NAID)
    130004677979
  • Text Lang
    JPN
  • ISSN
    1344-3992
  • Data Source
    J-STAGE 
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