Did Triadobatrachus Jump? Morphology and Evolution of the Anuran Forelimb in Relation to Locomotion in Early Salientians

Abstract The Lower Triassic amphibians Triadobatrachus massinoti and Czatkobatrachus polonicus are universally regarded as stem anurans. However, there is still uncertainty about whether or not they were capable of jumping like true anurans as their postcranial features have so far provided only equivocal evidence. Although previous work has concentrated on the anatomy of the hind limb, here we examine the anatomy of the forelimb, comparing stem and crown-group anurans to other amphibians. The forelimb and pectoral girdle of Triadobatrachus share several features with modern frogs, including a frog-like deltoid attachment of the scapula. Though the radius and ulna are unfused, the humerus is similar to those of modern anurans. The deltopectoral crest is slightly elongated and a lateral deflection of the ventral edge of the crest creates a concavity on the lateral face of the humerus. These features are uncommon in most tetrapod groups characterized by a sprawling stance but are typical of modern anurans, ...