蜥臀目霸王龙及有鳞目沧龙牙齿组织的微细结构

本文是利用扫描电子显微镜对陆栖恐龙tvrannosaurid与海栖渐增mosasaurid”牙齿结构进行的比较解剖学研究。化石采自加拿大RedDeerhiverValley上白里统Horse－shoeCanyon组。通过研究地层中出现的生物化石，特别是动物牙齿的组织结构，可以了解动物为了适应生活环境而发生的进化过程，也可以推测它们的系统发育关系。tyrannosaund与mosas。id都拥有锥状的同形齿，牙齿侧向扁平，且略向后弯曲。研究结果确认了tyrannosaurid的牙齿由于薄层的无柱釉质bPrismaticenamel）向齿质的侵人而造成许多的凹凸构造，此锯齿状构造沿着牙齿的前后缘，由牙齿的顶端分布至基部。因此tyrannosaurid的牙齿呈现着锐利的切缘；在这些凹凸状切缘的沟与小窝的深部可观察到有机物的沉积。但是类似的锯齿状构造只能在齿冠呈钝圆状的mosasaurid牙齿的基部附近观察到。我们以扫描电子显微镜（SEM）检索，确认两爬行类的齿质皆是属于中间型的真性齿质（intermediatetypeorthodentine）；所谓orthodentine即是细管齿质（tubulardentine）。tyrannosaurid的真性齿质的齿质小管只在齿质一釉质相接处Uentino—enamaljunction）附近放散出规则性的分歧与末枝。但mosasaurid的真性齿质的齿质J。管，在齿质的中间层与表层中，呈现着由复杂

FINE STRUCTURE OF DENTAL TISSUES IN TEETH OF SAURISCHIAN TYRANNOSAURID AND SQUAMATE MOSASAURID

Tceth of saurischian tyrannosaurid and squamate mosasaurid are studiedmainly by scanning electron microscopy. The teeth of both diapsids are cone-shapedhomodontic teeth mediolaterally compressed and curved posteriorly. The sharp cuttingedges at both anterior and posterior aspects of tyrannosaurid tooth are serrated withinvagination of a quite thin aprismatic enamel layer. Fissures and pits of theinvaginations are packed with what is possibly a layer of fossilized organic substance.In contrast, similar serrated cutting edges are only observed at the basal portion oflepidosaurian mosasaurid teeth. The present scanning electron microscopy (SEM) observes a similar intermediate type orthodentine (tubular dentine) with ill-developedperitubular dentine of both extinct reptiles. SEM reveals that dentinal tubules are regularly branched only in the vicinity of the flat dentino-enamel junction intyrannosaurid tubular dentinc, but are complicatedly branched in the mid - andsuperficial-layer of mosasaurid dentine. The present study also shows a few dentinaltubules invaded the enamel layer, with a similar configuration and an evidentdistribution of interglobular dentine beneath the thin enamel layer of both reptiles.Based on the present fine structure study, We elucidates some histological similaritiesand dissimilarities of the enamel and dentine in the reptilian tyrannosaurid andmosasaurid of different infraclasses.