Main mechanical challenge
The results of the analyses focusing on the main mechanical challenge
show that the teeth of durophagous species are different from those of
species that need extensive manipulation of their prey (bulky, hard,
hold). The hard prey group is characterized by teeth that are short,
stout, with the smallest mean and maximal curvature (Fig. 3 & 5). Their
pulp cavity is the short and the relative thickness of hard tissue is
greater than for the other groups, making their teeth more robust. On
the opposite, slippery prey eaters are characterized by long, slender,
and highly curved teeth (Fig. 3 & 5). Their pulp cavity is long and
provides the teeth with a relatively thin layer of hard tissue which may
allow more bending, but this hypothesis remains to be tested.
This main mechanical challenge category shows us that the morphology of
snake teeth can be divided into two groups. Slippery, bulky, and species
holding their prey have similar teeth, and their distribution largely
overlaps in the morphospace, while species feeding on hard and long prey
are similar and overlap but they barely overlap with the other
categories (Fig. 4). There are only two species that do not fit in their
group: Atractaspis engaddensis and Atractus flammigerus .Atractaspis engaddensis falls within the durophagous group
whereas it mostly feeds on small mammals (it would be classified as a
bulky eater). Atractaspids are specialized fossorial snakes, they have
developed a highly specialized envenomation strategy which consists of a
highly mobile maxilla that can laterally protrude the fang, while the
mouth remains closed, allowing the snake to stab its prey backwards. Its
dentigerous bones are almost toothless and the hyper specialization of
the envenomation system is associated with a loss of prey manipulation
and transport efficiency (Deufel & Cundall, 2003). A high rate of prey
loss in durophagous snakes also having short and stout teeth has been
demonstrated (Gripshover & Jayne, 2021), suggesting that this tooth
shape may not have evolved to manipulate the prey but rather to prevent
breakage. Atractus flammigerus, on the other hand, is an
earthworm specialist classified in the “long prey” group but falls
into the “slippery” category in the morphospace (Fig. 4). We strictly
defined our main mechanical challenges a priori and classified
elongated prey as more constraining than slippery prey, butAtractus teeth look more like slippery prey feeders.