An arboreal rhynchocephalian from the Late Jurassic of Germany, and the importance of the appendicular skeleton for ecomorphology in lepidosaurs

Here, we describe a new species of Jurassic rhynchocephalian from the Solnhofen Archipelago, Sphenodraco scandentis gen. et sp. nov., and highlight the importance of the postcranial anatomy for ecomorphological studies in the rhynchocephalian clade. The holotype of Sphenodraco scandentis is divided into a main slab, which has been mentioned in the literature and previously assigned to Homoeosaurus maximiliani, and a counterslab containing most of its skeletal remains. This new taxon shows an exclusive combination of osteological features that differs from previously described rhynchocephalians. Sphenodraco was recovered in our phylogenetic analysis as a component of a clade including Homoeosaurus and Kallimodon. To evaluate the ecomorphology of the new taxon, we compare fossil rhynchocephalians with the extant tuatara and squamates. We quantify the diversity of body proportions in lepidosaurs systematically, inferring lifestyle for extinct rhynchocephalians. Our analysis suggests that fossil rhynchocephalians had a diverse array of substrate uses, with some categorized as good climbers, and with Sphenodraco showing the extreme condition of limb elongation found in strictly arboreal lizards. This new taxon is here regarded as the first predominantly or even strictly arboreal rhynchocephalian. Furthermore, our analysis shows that the diversity of fossil rhynchocephalians might still be underestimated.