Data from: Walk before you jump: new insights on early frog locomotion from the oldest known salientian

Understanding the evolution of a Bauplan starts with discriminating
phylogenetic signal from adaptation and the latter from exaptation in the
observed biodiversity. Whether traits have predated, accompanied, or
followed evolution of particular functions is the basic inference to
establish the type of explanations required to determine morphological
evolution. To accomplish this, we focus in a particular group of
vertebrates, the anurans. Frogs and toads have a unique Bauplan among
vertebrates, with a set of postcranial features that have been considered
adaptations to jumping locomotion since their evolutionary origin. This
interpretation is frequently stated but rarely tested in scientific
literature. We test this assumption reconstructing the locomotor
capabilities of the earliest known salientian, Triadobatrachus massinoti.
This extinct taxon exhibits a mosaic of features that have traditionally
been considered as representing an intermediate stage in the evolution of
the anuran Bauplan, some of which were also linked to jumping skills. We
considered T. massinoti in an explicit evolutionary framework by means of
multivariate analyses and comparative phylogenetic methods. We used length
measurements of major limb bones of 188 extant limbed amphibians (frogs
and salamanders) and lizards as a morphological proxy of observed
locomotor behavior. Our findings show that limb data correlate with
locomotion, regardless of phylogenetic relatedness, and indicate that
salamander-like lateral undulatory movements were the main mode of
locomotion of T. massinoti. These results contrast with recent hypotheses
and indicate that derived postcranial features that T. massinoti shared
with anurans might have been later co-opted as exaptations in jumping
frogs.