Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY 11794-5425, USA.
Am J Phys Anthropol. 2010 Jun;142(2):194-210. doi: 10.1002/ajpa.21211.
Plesiadapis cookei is an extinct relative of extant euarchontans (primates, dermopterans; scandentians), which lived in North America during the late Paleocene. P. cookei body mass has been estimated to be approximately 2.2 kg, making it large compared with other species of its genus from North America, but similar to some from Europe. In particular, size as well as dental form similarities to P. russelli have been noted. However, it is thought that P. russelli evolved from P. tricuspidens, and into Platychoerops daubrei. Dental similarities among P. cookei, P. russelli, and P. daubrei have been hypothesized to reflect a more folivorous diet than utilized by P. tricuspidens. Here we test the hypothesis that P. cookei is more dietarily specialized than P. tricuspidens by quantifying functionally significant aspects of molar, premolar, and incisor forms. Casts of M(2)s and P(4)s of P. tricuspidens, P. cookei, and P. daubrei were microCT-scanned. We measured the relief index and/or the complexity from surface reconstructions of scans. Results show that P. cookei has higher M(2) relief and complexity than P. tricuspidens; P. daubrei exhibits the highest relief and complexity. Similarly, P. cookei has a more complex P(4) than P. tricuspidens, whereas that of P. daubrei exhibits the highest complexity. Finally, the I(1) of P. cookei resembles more the incisor of P. daubrei than that of P. tricuspidens. Because high relief and complexity of dentitions are related to fibrous plant diets in living mammals, these findings support the hypothesis that previously identified similarities among P. cookei, P. russelli and P. daubrei reflect a folivorous diet.
古灵长总目动物（灵长目、皮翼目、攀兽目）的绝灭近亲——古鼩猬属的古鼩猬（Plesiadapis cookei），生活在北美洲的渐新世晚期。古鼩猬的体重估计约为 2.2 公斤，与北美的其他种相比体型较大，但与一些欧洲种相似。特别是，它的体型以及与 P. russelli 的牙齿形态相似。然而，人们认为 P. russelli 是从 P. tricuspidens 进化而来，然后演变成 Platychoerops daubrei。古鼩猬、P. russelli 和 P. daubrei 之间的牙齿相似性被认为反映了一种比 P. tricuspidens 更偏向于食叶的饮食。在这里，我们通过量化磨牙、前臼齿和门齿形态的功能显著方面，来检验古鼩猬比 P. tricuspidens 更具饮食特化性的假设。我们对 P. tricuspidens、P. cookei 和 P. daubrei 的 M(2)和 P(4)牙模进行了微 CT 扫描。我们从扫描的表面重建中测量了 Relief Index 和/或复杂性。结果表明，古鼩猬的 M(2) Relief 和复杂性高于 P. tricuspidens；P. daubrei 的 Relief 和复杂性最高。同样，古鼩猬的 P(4)比 P. tricuspidens 更复杂，而 P. daubrei 的 P(4)则具有最高的复杂性。最后，古鼩猬的 I(1)更类似于 P. daubrei 的门齿，而不是 P. tricuspidens 的门齿。因为在现生哺乳动物中，高 Relief 和复杂性的牙齿与纤维植物饮食有关，这些发现支持了这样一种假设，即先前在 P. cookei、P. russelli 和 P. daubrei 之间发现的相似性反映了一种食叶的饮食。
