亚洲三种冠齿兽类的齿冠形成时间及其对选取现生类似种的参考意义(英文)

Tooth crown formation time in three Asian coryphodontids,and its implications for identifying living analogues

选取了亚洲常见的三种冠齿兽类Asiocoryphodon conicus Xu,1976,Heterocoryphodon fl erowi(Chow,1957)和Eudinoceras mongoliensis Osborn,1924,对其臼齿材料进行组织学切片研究,以讨论多尖牙齿齿冠形成模式和估算它们的齿冠形成时间。结果显示,A.conicus,H.fl erowi和E.mongoliensis上第三臼齿齿冠的形成时间分别为2.99±0.1,3.63±0.11和3.68±0.22 yr,三种冠齿兽类的生活史均符合慢生长、长生命型模式。综合考虑体型的影响,相较其他大型植食性动物,H.fl erowi的生活史更适合与现生河马(Hippopotamus amphibius)进行类比,E.mongoliensis的生活史更适合与白犀(Ceratotherium simum)进行类比,而A.conicus的生活史则稍快稍短于现生河马。这些现生类似种的种内变化数据可为冠齿兽类的部分分类学问题提供参考。

Molar enamel samples of three Asian coryphodontid species, Asiocoryphodon conicus Xu, 1976, Heterocoryphodon flerowi （Chow, 1957） and Eudinoceras mongoliensis Osborn, 1924, were histologically studied in order to investigate the patterns of formation of their multi- cusped tooth crowns and estimate their tooth crown formation times. The third upper molar crown formation times ofA. conicus, H.flerowi and E. mongoliensis were estimated to have been 2.99 ± 0.1, 3.63 ± 0.11 and 3.68 ± 0.22 years, respectively, suggesting slow growth and a long life span. In combination with the inferred body sizes, the estimated crown formation times indicate that the life history of H. flerowi is most comparable to that of Hippopotamus amphibius among extant large herbivores, that the life history of E. mongoliensis is most properly compared with that of Ceratotherium simum, and that the life history of A. conicus was slightly shorter and faster-paced than that of Hippopotamus amphibius. Appropriate extant analogues for which data on intraspecific variation are available can be potentially helpful in better understanding the classification and phylogeny of coryphodontids, a highly diverse group of Cenozoic early mammals.