Data from: Australian rodents reveal conserved craniofacial evolutionary allometry across 10 million years of murid evolution

Among vertebrates, placental mammals are particularly variable in the
covariance between cranial shape and body size (allometry), with rodents a
major exception. Australian murid rodents allow an assessment of the cause
of this anomaly because they radiated on an ecologically diverse continent
notably lacking other terrestrial placentals. Here we use 3D geometric
morphometrics to quantify species-level and evolutionary allometries in 38
species (317 crania) from all Australian murid genera. We ask if
ecological opportunity resulted in greater allometric diversity compared
to other rodents, or if conserved allometry suggests intrinsic constraints
and/or stabilizing selection. We also assess whether cranial shape
variation follows the proposed “rule of craniofacial evolutionary
allometry” (CREA), whereby larger species have relatively longer snouts
and smaller braincases. To ensure we could differentiate parallel versus
non-parallel species-level allometric slopes, we compared the slopes of
rarefied samples across all clades. We found exceedingly conserved
allometry and CREA-like patterns across the 10 million year split between
Mus and Australian murids. This could support both intrinsic constraints
and stabilizing selection hypotheses for conserved allometry. Large-bodied
frugivores evolved faster than other species along the allometric
trajectory, which could suggest stabilizing selection on the shape of the
masticatory apparatus as body size changes.