Allometry and function of primate pelves

Abstract

Functional inference of locomotion in fossil primate pelves is difficult due to the effects of body size, phylogeny, and other non‐locomotor functions on pelvic shape. This study examines size and scaling of pelvic anatomy using phylogenetic comparative methods to determine aspects of the pelvis that may be affected by the loading requirements of both locomotor mode and body size. Three‐dimensional landmark data were collected on 787 pelves from 40 taxa ranging in mean body size from 0.25 to 270 kg. Ten linear dimensions were calculated and phylogenetic reduced major axis regressions were performed for each pelvic dimension on overall pelvic size at several taxonomic levels. At the primate‐wide level, tests of the null hypothesis of isometric scaling of pelvic dimensions were rejected for some ilium dimensions and for the cross‐sectional areas of the ilium and ischium, dimensions that have been suggested to be strongly related to the effects of locomotor loading. The height of the lower ilium scales with negative allometry, while ilium width and the cross‐sectional area of the ilium and ischium all scale with strong positive allometry; tests for Catarrhini, Platyrrhini, Lemuriformes, and Lorisiformes support the primate‐wide results (all results significant at p<0.05). These results suggest that as body size increases—and forces due to loading increase—the height of the ilium decreases to mitigate bending stresses, while the areas of the ilium and ischium increase to reduce bone strain. Primate pelvic anatomy is likely adapted to the combined effects of loading due to large body size and locomotion.Grant Funding Source: NSF‐BCS #075–2575, The Leakey Foundation