Can social and sexual selection explain the bizarre snout of proterosuchid archosauriforms?

EZCURRA, M. D.

Historical Biology

Taylor and Francis

Año: 2016

Proterosuchids are a clade of quadrupedal, carnivorous Permo-Triassic diapsids crucial to understandthe successful evolutionary radiation of archosaurs during the Mesozoic. The importance and good fossilrecord of proterosuchids nourished a renewed interest in recent years, but no function has been proposedfor their bizarre snouts. An oversized and downturned premaxilla with up to nine teeth with continuousreplacement is present in all proterosuchid species and seems to have represented a physiologically costlyphenotype that increased towards adulthood. A non-functional or a species recognition hypothesis arenot supported as evolutionary mechanisms that drove this phenotype because features expected forthese explanations tend to have a very low or zero physiological cost. There is no evidence favouring ? butneither rejecting − that this morphology can be explained by non-sexual and non-social natural selectionalone. Mutual social and/or sexual selection is favoured here as the most unambiguously supportedexplanation for the function and origin of the bizarre snout of proterosuchids based on several lines ofevidence, including costliness, positive allometry, positive changes in growth rates and modern analogues.Social and/or sexual selection may have been important evolutionary mechanism in the dawn of thelineage that gave rise to crocodiles and dinosaurs.