The idea makes sense, says Theo Busschau, an evolutionary biologist at New York University Abu Dhabi. These might make them more conspicuous to prey and predators because a structure that enlarges their head and silhouette may render them more visible while moving.” “Animals that need to move a lot may be disadvantaged by possessing large appendages over their heads. Horns might be a boon for some species, but a burden in others, Banfi says. Of horned squamates, 164 - 94 percent - were also relatively stationary ambush hunters, with just 11 - 6 percent - categorized as active predators. Sure enough, horns were much more common in sit-and-wait predators than in their more active counterparts. The team mapped the presence or absence of horns and the reptiles’ hunting style onto a previously published squamate evolutionary tree, finding the projections evolved independently about 69 times. The team compiled previously published datasets that classified lizards and snakes as either sit-and-wait predators or active pursuers, yielding 1,939 different species with 175 that had horns - defined as projections of bone or keratin on the animal’s snout, eyebrows or head. If not, or if horns hinder the animal’s movements, this might discourage the protuberances from evolving in more active species. But Federico Banfi, a herpetologist at the University of Antwerp in Belgium, and his colleagues wondered whether horns’ camouflage benefits still help animals that move around a lot when hunting. Prior studies suggested these ornaments may have different functions, such as being used in courtship, defense or breaking up the body outline to evade detection. Squamates - lizards and snakes - have repeatedly evolved horns atop their heads, on their eyebrows and jutting out from their snouts ( SN: 6/9/20).
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