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Wear facet morphology and evolution of occlusal function in Proboscidea

长鼻类磨损面形态及咬合功能的演化

基本信息

批准号：
11640467
负责人：
SAEGUSA Haruo
金额：
$ 1.28万
依托单位：
Himeji Insititute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Cheek teeth of Phiomia were examined qualitatively under SEM in an attempt to recognize basic wear pattern of cheek teeth in Elephantoidea. In Phiomia, wear facets of molars can be classified into three categories; facet with distinct margin formed by tooth to tooth contact, and inner and outer abrasion facets with vague margin formed by tooth to food contact. Parallel striae with ligualobuccal orientation are developed on valley slopes and the outer abrasion facet, while pits dominate on inner abrasion facet, central conule and apex of posttrite cones. Wear pattern seen in Phiomia must have been formed by deep interlocking between valley and ridges of molars during trituration of food.Some of non-tetralophodont gomphotheres, such as Sinomastodon and the mammutid Zygolophodon, retain wear pattern seen in Phiomia. However, wear feature in Gomphotherium, Cuvieronius, Anancus, Stegodontidae and Elephantidea differs from that of Phiomia in that striae are found also on inner abrasion surface. The latter wear pattern must be formed by shallow or no interlocking between valley and ridges of molars during mastication.A deformed skull of stegolophodon from Japanese Miocene was reconstructed. The reconstruction suggested that some Japanese stegolophodons could be dwarf form, which is the oldest example proboscidean dwaft.

在扫描电镜下对象鼻虫颊齿进行了定性观察，试图了解象鼻虫总科颊齿的基本磨损模式。在Phiomia中，磨牙的磨损小平面可以分为三类：由牙齿与牙齿接触形成的具有明显边缘的小平面，以及由牙齿与食物接触形成的具有模糊边缘的内磨损小平面和外磨损小平面。在山谷斜坡和外剥蚀面上发育舌颊走向的平行条纹，在内剥蚀面、中央锥和后锥的顶端则以纹孔为主。在Phiomia中看到的磨损模式一定是在研磨食物时臼齿的谷和脊之间的深联锁形成的。一些非四棱兽类的楔齿兽，如中国乳齿象和哺乳动物Zygolophodon，保留了在Phiomia中看到的磨损模式。而锥齿兽、Cuvieronius、Anancus、剑齿兽科和象亚目的磨损特征与Phiomia的磨损特征不同，它们的内磨损表面上也有条纹。后一种磨损模式是由磨牙在咀嚼过程中的齿沟和齿脊之间的浅交锁或无交锁形成的。重建表明，一些日本剑齿虎可能是侏儒型，这是最古老的长鼻类侏儒型。