The evolution of encephalization in caniform carnivorans.

Area of Science:

• Paleontology
• Evolutionary Biology
• Comparative Anatomy

Background:

• Estimating fossil endocranial volume (brain size) is crucial for understanding evolutionary trends.
• Existing models for extant (living) species may not accurately apply to extinct taxa.
• The mammalian order Carnivora, particularly the suborder Caniformia, offers a rich fossil record for evolutionary study.

Purpose of the Study:

• To validate a weighted-average model for estimating endocranial volume in fossil carnivorans.
• To expand the dataset of fossil taxa with known brain volumes within Caniformia.
• To comprehensively assess the evolution of relative brain size (encephalization) across Caniformia.

Main Methods:

• A weighted-average model, validated on extant Carnivora, was applied to fossil taxa.
• Endocranial volumes were estimated and compared to known endocast volumes for fossil and extant species.
• Allometry of brain volume to body mass was calculated, and log-transformed encephalization quotients (logEQs) were computed for extant and fossil taxa.

Main Results:

• The model accurately estimated endocranial volumes for diverse fossil carnivorans, including crown and stem taxa.
• The study expanded the number of Caniformia with estimated brain volumes from 11 to 60 taxa.
• Early caniforms exhibited significantly lower median logEQs than extant taxa, with a notable shift around the Miocene-Pliocene boundary.

Conclusions:

• The weighted-average model is reliable for estimating endocranial volumes in fossil carnivorans.
• Relative brain size in Caniformia has increased gradually over evolutionary time, with parallel increases across major clades.
• The extinct family Amphicyonidae shows unique brain-to-body size scaling patterns potentially due to specific allometry.