Digest: Craniofacial morphology diversification in Malagasy primates and the role of size constraints in adaptive radiation

How did size-related evolutionary constraints shape the diversification of craniofacial morphology during the adaptive radiation of Malagasy lemurs? Toyoda (2025) employed geometric morphometrics to investigate craniofacial variation across Madagascar primates. The findings suggest that small-bodied lemurs exhibit a conserved craniofacial form-short rostra and large orbits-driven by mechanical and developmental constraints, yet adapt ecological specialization through rostral modifications. Large-bodied lemurs, in contrast, show greater cranial disparity, indicating a relaxation of size-related constraints. These findings underscore that evolutionary constraints do not merely limit diversification but instead channel morphological evolution along distinct, size-dependent trajectories during adaptive radiation.