Fancy frills and mighty bites: frill function in the late Permian Weigeltisauridae (Diapsida)
Résumé
The Weigeltisauridae, known from the Lopingian of Madagascar, Germany, England and Russia, are the first known gliding reptiles – and vertebrates. Despite their gliding capacity being commonly accepted, the significance of their unique, highly ornamented cranial morphology remains poorly understood.
The detailed examination of weigeltisaurid specimens from Madagascar and Germany based on direct observation and Computed Laminography allowed for a complete redescription and reconstruction of the cranium of weigeltisaurids. The skull of these animals forms an elongate frill at the back of the head, adorned with several bony spikes, and is strongly reminiscent of the head of extant chamaeleonids and ceratopsian dinosaurs.
While the presence of the frill is not sexually dimorphic, as in more recent reptiles, the length, shape and ornamentation of the frills show substantial interspecific variability. The frill bones bear sharp elongate crests indicating a broad surface of origin for the temporal musculature in weigeltisaurids, suggesting an increased bite force compared with similar-sized reptiles. Similar morphologies and increased bite forces have been described in chamaeleonid squamates and ceratopsian dinosaurs, indicating a convergent acquisition.
In addition, by analogy with extant frilled animals, we suggest that the highly ornamented frill of weigeltisaurids, adorned by tubers and spikes, may have served as a display structure, as a deterrent against predators or competitors, and as a defensive structure.