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.

在诸多哺乳类演化支中，体型更大的物种相较于其小型近亲，面部相对更长。该规律已在现生袋鼠（Macropodinae）类群中得到验证，它们遵循CREA正面部异速生长（positive facial allometry）法则；但迄今尚未有针对已灭绝短面袋鼠（Sthenurinae）的相关研究。本研究采用线性测量法（而非CREA相关技术），证实短面袋鼠的面部长度呈负异速生长（negative allometry）模式，因此与其现生近亲的演化趋势截然不同。