Postcranial osteogenesis of the helmeted water toad Calyptocephalella gayi (Neobatrachia: Calyptocephalellidae) with comments on the osteology of australobatrachians

MUZZOPAPPA, PAULA; PUGENER, ANALIA; BAEZ, A.M

JOURNAL OF MORPHOLOGY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New York; Año: 2016 vol. 277 p. 204 - 230

0362-2525

ABSTRACT Calyptocephalella gayi is one of over 6,000neobatrachians arranged into two main groups, Hyloidesand Ranoides. Phylogenetically, C. gayi is placed in Australobatrachia,a Gondwanan clade that is either the most basalclade of Hyloides or the sister group of Hyloidea, dependingon the cladistic hypothesis; as such, this species is a keytaxon in the study of the early evolution of Neobatrachia.The ontogeny of the postcranial skeleton of C. gayi isdescribed in this article. The description is based on patternof chondrification and ossification of skeletal elements in agrowth series of tadpoles, on juveniles and adult individuals.Particular attention was devoted to some developmentalaspects and morphological traits of the adult skeleton. Thebody of Presacral Vertebra VIII is formed from three centersof ossification, in contrast to the usual two dorsolateral centersobserved in the remaining vertebrae of C. gayi, as wellas in most anuran taxa for which the development of theaxial skeleton is known. Each half of the pelvic girdle arisesfrom a single cartilaginous element. The early developmentof the autopodia of both the forelimb and hindlimb includesthe presence of an additional chondral element, whichoccurs during the formation of Distal Carpal 5 and the transientformation of Distal Tarsal 4 before the latter is incorporatedin the cartilaginous distal end of the fibular. Someosteological aspects of other australobatrachian anuransalso are reviewed (e.g., presence of intervertebral discs)based on reports in the literature, as well as first handobservations. In the course of this study, it became evidentthat further osteological studies are needed to formulate aclear picture of the evolution of skeletal characters not onlywithin Australobatrachia, but also within Neobatrachia.