Footloose: Articular surface morphology and joint movement potential in the ankles of lorisids and cheirogaleids.

Journal Article (Journal Article)

OBJECTIVES: The competing functional demands of diarthrodial joints, permitting mobility while retaining enough stability to transmit forces across the joint, have been linked with the shape and size of the joint's articular surfaces. A clear understanding of the relationship between joint morphology and joint movement potential is important for reconstructing locomotor behaviors in fossil taxa. METHODS: In a sample of matched tali and calcanei of lorisids (n = 28) and cheirogaleids (n = 38), we quantify the surface areas of the talar and calcaneal ectal (=posterior talocalcaneal) articular surfaces and model the principal curvatures of these surfaces with quadric formulas. These two taxonomic groups have similar body masses, but differ substantially in positional behavior, so that differences in joint surface morphology should reflect adaptive demands of their locomotor behavior. RESULTS: Compared with cheirogaleids, lorisids exhibit: (a) a significantly greater area difference between their paired joint surfaces; and (b) a more pronounced saddle shape for the talar ectal facet. CONCLUSION: The increased subtalar joint mobility observed in lorisids may be achieved by increasing the amount of sliding and rolling that can occur at the subtalar joint. The subtalar joint morphology observed in two fossil euarchontans, the plesiadapiforms Purgatorius sp. and Plesiadapis cookei, compares favorably with the morphology observed among lorisids, potentially suggesting antipronograde postures within these extinct taxa.

Full Text

Duke Authors

Cited Authors

  • Yapuncich, GS; Granatosky, MC

Published Date

  • August 2021

Published In

Volume / Issue

  • 175 / 4

Start / End Page

  • 876 - 894

PubMed ID

  • 33931869

Electronic International Standard Serial Number (EISSN)

  • 1096-8644

Digital Object Identifier (DOI)

  • 10.1002/ajpa.24298

Language

  • eng

Conference Location

  • United States