Evolutionary patterns of cat-like carnivorans unveil drivers of the
sabertooth morphology

Highlights

There is a continuous spectrum of cat-like phenotypes with sporadic
convergence

Saber-toothed taxa show reduced integration and high early evolutionary
rates

Disparity is high among sabertooths, yet cat-like carnivorans decline
after the Miocene

The emergence of large sabertooths appears to act as a macroevolutionary
ratchet

Summary

The sabertooth morphology stands as a classic case of convergence,
manifesting recurrently across various vertebrate groups, prominently
within two carnivorans clades: felids and nimravids. Nonetheless, the
evolutionary mechanisms driving these recurring phenotypes remain
insufficiently understood, lacking a robust phylogenetic and
spatiotemporal framework. We reconstruct the tempo and mode of
craniomandibular evolution of Felidae and Nimravidae and evaluate the
strength of the dichotomy between conical and saber-toothed species, as
well as within saber-toothed morphotypes. To do so, we investigate
morphological variation, convergence, phenotypic integration, and
evolutionary rates, employing a comprehensive dataset of nearly 200 3D
models encompassing mandibles and crania from both extinct and extant
feline-like carnivorans, spanning their entire evolutionary timeline.
Our results reject the hypothesis of a distinctive sabertooth
morphology, revealing instead a continuous spectrum of feline-like
phenotypes in both the cranium and mandible, with sporadic instances of
unequivocal convergence. Disparity peaked at the end of the Miocene and
is usually higher in clades containing taxa with extreme sabertoothed
adaptations. We show that taxa with saberteeth exhibit a lower degree of
craniomandibular integration, allowing to exhibit a greater range of
phenotypes. Those same groups usually show a burst of morphological
evolutionary rate at the beginning of their evolutionary history.
Consequently, we propose that a reduced degree of integration coupled
with rapid evolutionary rates emerge as key components in the
development of a sabertooth morphology in multiple clades.

Open access:
https://www.cell.com/current-biology/fulltext/S0960-9822(24)00529-3