New material of Beelzebufo, a hyperossified frog (Amphibia: anura) from the Late Cretaceous of Madagascar

Abstract

The extant anuran fauna of Madagascar is exceptionally rich and almost completely endemic. In recent years, many new species have been described and understanding of the history and relationships of this fauna has been greatly advanced by molecular studies, but very little is known of the fossil history of frogs on the island. Beelzebufo ampinga, the first named pre-Holocene frog from Madagascar, was described in 2008 on the basis of numerous disarticulated cranial and postcranial elements from the Upper Cretaceous (Maastrichtian) Maevarano Formation of Madagascar. These specimens documented the presence of a hyperossified taxon that differed strikingly from extant Malagasy frogs in its large size and heavy coarse cranial exostosis. Here we describe and analyse new, articulated, and more complete material of the skull, vertebral column, and hind limb, as well as additional isolated elements discovered since 2008. μCT scans allow a detailed understanding of both internal and external morphology and permit a more accurate reconstruction. The new material shows Beelzebufo to have been even more bizarre than originally interpreted, with large posterolateral skull flanges and sculptured vertebral spine tables. The apparent absence of a tympanic membrane, the strong cranial exostosis, and vertebral morphology suggest it may have burrowed during seasonally arid conditions, which have been interpreted for the Maevarano Formation from independent sedimentological and taphonomic evidence. New phylogenetic analyses, incorporating both morphological and molecular data, continue to place Beelzebufo with hyloid rather than ranoid frogs. Within Hyloidea, Beelzebufo still groups with the South American Ceratophryidae thus continuing to pose difficulties with both biogeographic interpretations and prior molecular divergence dates.