Morphological convergence obscures functional diversity in sabre-toothed carnivores

The acquisition of elongated, sabre-like canines in multiple vertebrate
clades during the last 265 million years represents a remarkable example
for convergent evolution. Due to striking superficial similarities in the
cranial skeleton, the same or similar skull and jaw functions have been
inferred for sabre-toothed species and interpreted as an adaptation to
subdue large-bodied prey. However, although some sabre-tooth lineages have
been classified into different ecomorphs (dirk-tooths and scimitar-tooths)
the functional diversity within and between groups and the evolutionary
paths leading to these specialisations are unknown. Here, we use a suite
of biomechanical simulations to analyse key functional parameters
(mandibular gape angle, bending strength, bite force) to compare the
functional performance of different groups and to quantify evolutionary
rates across sabre-tooth vertebrates. Our results demonstrate a remarkably
high functional diversity between sabre-tooth lineages and that cranial
function and prey killing strategies evolved within clades. Moreover,
different biomechanical adaptations in coexisting sabre-tooth species
further suggest that this functional diversity was at least partially
driven by niche-partitioning.