Martin L
Nature. 1985;314(6008):260-3. doi: 10.1038/314260a0.
Enamel thickness has assumed unique importance in the debate about the hominid status of Ramapithecus, despite the fact that there is little agreement about the meaning of 'thick enamel' or the significance of enamel thickness for hominoid taxonomy. My aim here is to evaluate the usefulness of enamel thickness and microstructure as characteristics for determining the relationships of the later Miocene hominoids, based both on a quantitative study of enamel thickness in extant hominoids and four species of later Miocene Sivapithecus (including 'Ramapithecus') and on scanning electron microscope analysis of enamel microstructure. Four categories of enamel thickness are defined metrically here and have been related to enamel microstructure and developmental rates. Thin fast-formed (pattern 3) enamel represents the ancestral condition in hominoids; it increased developmentally to thick pattern 3 enamel in the great ape and human clade and that condition is primitively retained in Homo and in the fossil hominoid Sivapithecus (including 'Ramapithecus'). Enamel thickness has been secondarily reduced in the African apes and also, although at a different rate and extent, in the orang-utan. Thick enamel, previously the most important characteristic in arguments about the earliest hominid, does not therefore identify a hominid.
尽管对于“厚釉质”的含义或釉质厚度在类人猿分类学中的意义几乎没有达成共识，但釉质厚度在关于腊玛古猿的人科地位的争论中已具有独特的重要性。我在此的目的是基于对现存类人猿以及四种晚中新世西瓦古猿（包括“腊玛古猿”）的釉质厚度的定量研究，以及对釉质微观结构的扫描电子显微镜分析，来评估釉质厚度和微观结构作为确定晚中新世类人猿之间关系的特征的有用性。这里从度量上定义了四类釉质厚度，并将其与釉质微观结构和发育速率相关联。薄的快速形成的（模式3）釉质代表类人猿的原始状态；在大猩猩和人类分支中，它在发育过程中增加为厚的模式3釉质，并且这种状态在人类和化石类人猿西瓦古猿（包括“腊玛古猿”）中原始保留。在非洲猿类中，釉质厚度已次生减少，在猩猩中也是如此，尽管减少的速率和程度不同。因此，厚釉质以前在关于最早人科动物的争论中是最重要的特征，但它并不能确定一个人科动物。
