Evolution of Locomotor Abilities in Frogs: Evidence from the Mesozoic-Paleogene Fossil Record

PÉREZ-BEN, CELESTE M.; LIRES, ANDRÉS I.; GÓMEZ, RAÚL ORENCIO

Praga

Congreso; XII International Congress of Vertebrate Morphology; 2019

Limbs appear to have played a key role in the adaptive radiation of anurans (frogs), showing morphologies associated with diverse locomotor abilities. Particularly, it has been shown that these abilities correlate with variations in limb proportions, which evolved convergentlyacross the anuran tree. It has been proposed that early salientians (stem-group anurans) were good jumpers and that the origin of the bizarre anuran Bauplan might have been related to jumping adaptations. However, it has recently been shown that distinct postcranial morphologies shared by earliest salientians and frogs would not have originally been linked to a saltatory locomotion. Herein, we explore the evolution of limb proportions and locomotor abilities in Salientia over most of their history. Based on length measurements of the limb bones in more than 300 extant and 40 extinct species encompassingthe Mesozoic and the Paleogene we: 1) performed a PCA to investigate the occupation of the limb morphospace over geological time; and 2) inferred locomotor behaviors (i.e., jumping, swimming, hopping, walking, burrowing) in extinct species by LDA and FDA. In the reduced morphospace PC1-PC2, extant ?archaeobatrachians? and neobatrachiansoverlap, with the latter more widespread in all directions, and group according to locomotor behavior. Jurassic, Cretaceous, and Paleogene species also overlap between them and with extant taxa. Based on the classification of extinct taxa, the earliest inferred long-distance jumpers are from the Early Cretaceous, whereas Jurassic taxa, including Prosalirus, are recovered as hopper/walkers or swimmers. In conclusion, a limited range of limb  proportions has been convergently explored since the Jurassic, with new morphologies mostly evolving after the neobatrachian radiation. Interestingly, our results agree with recent work based on different lines of evidence and data suggesting that saltatory locomotion might have not evolved early among salientians.