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This study used 3D geometric morphometric analysis to investigate cranial evolution in rhinocerotoids across extinct and living species, examining how skull shape relates to horn presence, body size, and diet. The research found that rhinos deviated from the typical evolutionary pattern where larger species have proportionally longer faces, likely due to diverse cranial forms that evolved independently in response to varying horn morphologies and feeding strategies. Both hornless and horned species showed similar evolutionary rates, with cranial diversity arising through multiple episodes of accelerated evolution linked to morphological innovations and global climate cooling during the Cenozoic era.
Why it matters
Understanding how major morphological features like horns influence skull evolution in large herbivores provides insights into how anatomical innovations shape adaptive radiations. This research contributes to broader knowledge of mammalian evolutionary patterns and may inform conservation strategies for remaining rhinoceros species by clarifying their evolutionary constraints and adaptive potential.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Despite their currently scarce taxonomic diversity, rhinocerotoids were among the most evolutionarily successful clades of large herbivorous mammals throughout the Caenozoic. Within an array of morphological adaptations, the cranial horn represents the clades most remarkable and name-giving feature, imposing significant morpho-functional demands on the skull. In this paper, patterns and drivers of the rhinos cranial evolution were investigated for the first time by compiling a three-dimensional geometric morphometric dataset of living and extinct species. Multiple aspects of morphological evolution were explored using phylogenetic comparative methods, including craniofacial evolutionary allometry (CREA – tendency of larger species to have longer faces), phylogenetic constraints, and tempo of evolution. Cranial shape variation linked to horn presence and size evolved under a phylogenetically constrained framework, with a notable transition from hornless to horned species. Rhinos significantly deviated from CREA, likely due to diversity of cranial forms and proportions that evolved independently across the clade in response to varying horn morphologies and dietary habits. Hornless and horned rhinos exhibited similar rates of cranial evolution, and shape variation was obtained through multiple episodes of accelerated evolution. This highlights the role of morphological innovations and Caenozoic global cooling events in the emergence of phenotypic diversity.