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Sabretoothed Carnivores: Natural Selection or Sexual Selection?

From: Ben Creisler

A new non-dino paper in PLoS ONE that may be of interest:

Marcela Randau, Chris Carbone & Samuel T. Turvey (2013)
Canine Evolution in Sabretoothed Carnivores: Natural Selection or
Sexual Selection?
PLoS ONE 8(8): e72868.

The remarkable elongated upper canines of extinct sabretoothed
carnivorous mammals have been the subject of considerable speculation
on their adaptive function, but the absence of living analogues
prevents any direct inference about their evolution. We analysed
scaling relationships of the upper canines of 20 sabretoothed feliform
carnivores (Nimravidae, Barbourofelidae, Machairodontinae),
representing both dirk-toothed and scimitar-toothed sabretooth
ecomorphs, and 33 non-sabretoothed felids in relation to body size in
order to characterize and identify the evolutionary processes driving
their development, using the scaling relationships of carnassial teeth
in both groups as a control. Carnassials display isometric allometry
in both sabretooths and non-sabretooths, supporting their close
relationship with meat-slicing, whereas the upper canines of both
groups display positive allometry with body size. Whereas there is no
statistical difference in allometry of upper canine height between
dirk-toothed and scimitar-toothed sabretooth ecomorphs, the
significantly stronger positive allometry of upper canine height shown
by sabretooths as a whole compared to non-sabretooths reveals that
different processes drove canine evolution in these groups. Although
sabretoothed canines must still have been effective for prey capture
and processing by hypercarnivorous predators, canine morphology in
these extinct carnivores was likely to have been driven to a greater
extent by sexual selection than in non-sabretooths. Scaling
relationships therefore indicate the probable importance of sexual
selection in the evolution of the hypertrophied sabretooth anterior