RESUMO
Calyptocephalella gayi is one of over 6,000 neobatrachians arranged into two main groups, Hyloides and Ranoides. Phylogenetically, C. gayi is placed in Australobatrachia, a Gondwanan clade that is either the most basal clade of Hyloides or the sister group of Hyloidea, depending on the cladistic hypothesis; as such, this species is a key taxon in the study of the early evolution of Neobatrachia. The ontogeny of the postcranial skeleton of C. gayi is described in this article. The description is based on pattern of chondrification and ossification of skeletal elements in a growth series of tadpoles, on juveniles and adult individuals. Particular attention was devoted to some developmental aspects and morphological traits of the adult skeleton. The body of Presacral Vertebra VIII is formed from three centers of ossification, in contrast to the usual two dorsolateral centers observed in the remaining vertebrae of C. gayi, as well as in most anuran taxa for which the development of the axial skeleton is known. Each half of the pelvic girdle arises from a single cartilaginous element. The early development of the autopodia of both the forelimb and hindlimb includes the presence of an additional chondral element, which occurs during the formation of Distal Carpal 5 and the transient formation of Distal Tarsal 4 before the latter is incorporated in the cartilaginous distal end of the fibular. Some osteological aspects of other australobatrachian anurans also are reviewed (e.g., presence of intervertebral discs) based on reports in the literature, as well as first hand observations. In the course of this study, it became evident that further osteological studies are needed to formulate a clear picture of the evolution of skeletal characters not only within Australobatrachia, but also within Neobatrachia.
Assuntos
Evolução Biológica , Bufonidae/anatomia & histologia , Osteogênese , Adolescente , Animais , Bufonidae/genética , Bufonidae/crescimento & desenvolvimento , Cartilagem/anatomia & histologia , Membro Anterior/anatomia & histologia , Membro Posterior/anatomia & histologia , Humanos , Pelve/anatomia & histologia , FilogeniaRESUMO
BACKGROUND: Teleosts constitute more than 99 % of living actinopterygian fishes and fossil teleosts have been studied for about two centuries. However, a general consensus on the definition of Teleostei and the relationships among the major teleostean clades has not been achieved. Our current ideas on the origin and early diversification of teleosts are mainly based on well-known Mesozoic marine taxa, whereas the taxonomy and phylogenetic relationships of many Jurassic continental teleosts are still poorly understood despite their importance to shed light on the early evolutionary history of this group. Here, we explore the phylogenetic relationships of the Late Jurassic (Oxfordian - Tithonian) freshwater Luisiella feruglioi from Patagonia, in a comprehensive parsimony analysis after a thorough revision of characters from previous phylogenetic studies on Mesozoic teleosts. RESULTS: We retrieved Luisiella feruglioi as the sister taxon of the Late Jurassic Cavenderichthys talbragarensis, both taxa in turn forming a monophyletic group with the Early Cretaceous Leptolepis koonwarri. This new so far exclusively Gondwanan freshwater teleost clade, named Luisiellidae fam. nov. herein, is placed outside crown Teleostei, as a member of the stem-group immediately above the level of Leptolepis coryphaenoides. In addition, we did not retrieve the Late Jurassic Varasichthyidae as a member of Crossognathiformes. The position of Crossognathiformes within Teleocephala is confirmed whereas Varasichthyidae is placed on the stem. CONCLUSIONS: The general morphology of luisiellids is that of basal, stem Teleocephala; however, most of their synapomorphies have evolved independently in teleocephalans. Similarly, the resemblance between varasichthyids and crossognathiforms might be due to parallel evolution. In accordance to most teleostean phylogenies, our analysis shows that a major morphological change occurred along the stem line and are currently recorded at the level of Leptolepis coryphaenoides. A stem-based total clade Teleostei has been accepted for this work.