Functional Anatomy and Evolution, Johns Hopkins University, Baltimore, MD, 21205.
Am J Phys Anthropol. 2014 Jan;153(1):15-28. doi: 10.1002/ajpa.22387. Epub 2013 Oct 18.
The earliest euprimates to arrive in North America were larger-bodied notharctids and smaller-bodied omomyids. Through the Eocene, notharctids generally continued to increase in body size, whereas omomyids generally radiated within small- and increasingly mid-sized niches in the middle Eocene. This study examines the influence of changing body size and diet on the evolution of the lower fourth premolar in Eocene euprimates. The P4 displays considerable morphological variability in these taxa. Despite the fact that most studies of primate dental morphology have focused on the molars, P4 can also provide important paleoecological insights. We analyzed the P4 from 177 euprimate specimens, representing 35 species (11 notharctids and 24 omomyids), in three time bins of approximately equal duration: early Wasatchian, late Wasatchian, and Bridgerian. Two-dimensional surface landmarks were collected from lingual photographs, capturing important variation in cusp position and tooth shape. Disparity metrics were calculated and compared for the three time bins. In the early Eocene, notharctids have a more molarized P4 than omomyids. During the Bridgerian, expanding body size range of omomyids was accompanied by a significant increase in P4 disparity and convergent evolution of the semimolariform condition in the largest omomyines. P4 morphology relates to diet in early euprimates, although patterns vary between families.
最早到达北美的真灵长类动物是体型较大的已绝灭的负鼠猴和体型较小的兔猴。在始新世，负鼠猴的体型一般继续增大，而兔猴则在中始新世的小型和中型生态位中多样化。本研究考察了体型和饮食的变化对始新世真灵长类动物下第四前臼齿进化的影响。在这些类群中，P4 表现出相当大的形态变异性。尽管大多数灵长类牙齿形态的研究都集中在臼齿上，但 P4 也可以提供重要的古生态学见解。我们分析了来自 177 个真灵长类标本的 P4，代表了 35 个物种（11 种负鼠猴和 24 种兔猴），分为三个时间间隔，每个间隔的持续时间大致相等：早沃萨奇期、晚沃萨奇期和布里杰期。从舌侧照片中采集了二维表面标志点，捕捉了小尖位置和牙齿形状的重要变化。为三个时间间隔计算并比较了离散度量。在始新世早期，负鼠猴的 P4 比兔猴更具臼齿化特征。在布里杰期，兔猴的体型范围扩大，同时 P4 的离散度显著增加，最大的兔猴的半尖齿化形态也发生了趋同进化。尽管模式在不同的科之间有所不同，但 P4 形态与早期真灵长类的饮食有关。
