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.
Highlights
Madagascar is a large island landmass separated from Africa by the wide and deep Mozambique Channel
Recovery of a much larger sample from the Maevarano Formation, including both cranial and postcranial elements, over the course of several subsequent expeditions permitted the description of a new genus and species, Beelzebufo ampinga [26], a large broad-headed, hyperossified, terrestrial anuran, unlike any that exists on Madagascar today
These data volumes were employed to generate surfaces used as digital models, both for this study and for general documentation and curation of data in ongoing efforts undertaken by the Mahajanga Basin Project. mCT datasets range in voxel size from 40–16 mm3, and were typically scanned at 70 kV and 114 mA
Summary
Madagascar is a large island landmass separated from Africa by the wide and deep Mozambique Channel It has a unique and diverse herpetofauna including around 250 species of anurans [1,2,3,4,5,6], with an estimated 200 or more remaining to be described [7,8]. This, in turn, was taken to indicate support for the hypothesis of a link between South America and Madagascar via Antarctica and the Kerguelen Plateau until the later stages of the Late Cretaceous [28]. Both the phylogenetic and palaeogeographical hypotheses of Evans et al [26] have subsequently been challenged. Ali and Aitchison [31,32] (see [33]) rejected the palaeogeographical scenario of Hay et al [28] on the basis of more recent geophysical and geological evidence demonstrating that connections between Antarctica and Indo-Madagascar were severed by the Middle Aptian (,115–120 Ma), and that only a small fraction of the Kerguelen Plateau was emergent in the later stages of the Late Cretaceous
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