Why the short face? The face lengths of sthenurine kangaroos scale with negative allometry

The larger species in many mammalian clades have relatively longer faces than their smaller relatives. This has been shown to be true for extant kangaroos (Macropodinae), who follow the CREA rule of positive facial allometry; but the extinct short-faced kangaroos (Sthenurinae) have not so far been examined. Using linear measurements, rather than CREA techniques, we show here that sthenurine face lengths scale with negative allometry, thus differing from the trend seen in their extant relatives.

在许多哺乳动物演化支（clade）中，体型更大的物种相较于其体型更小的近亲，面部相对更长。这一规律已在现存袋鼠亚科（Macropodinae）类群中得到证实，它们遵循面部正异速生长的CREA规则；但目前尚未对已灭绝的短面袋鼠亚科（Sthenurinae）开展相关研究。本研究采用线性测量而非CREA相关技术开展分析，结果表明短面袋鼠亚科的面部长度呈负异速生长模式，这与其现存近亲的演化趋势截然不同。