Phylogeny of the Cyprinodontiformes (Teleostei, Atherinomorpha): the contribution of cranial soft tissue characters

摘要

This study presents a cladistic analysis of the Cyprinodontiformes based on a comparative anatomical examination of 95 species. Seventy-eight characters of musculature, connective tissue elements and nervous system of the jaw apparatus are described, in many cases for the first time. In order to investigate the contribution of such soft tissue traits, the new data have been analysed separately and in combination with an extensive data matrix of morphological, primarily osteological characters produced by Costa using the NONA software. The inclusion of soft tissue characters led to the description of numerous additional apomorphies and to an improved resolution of the consensus topologies in the combined analysis. Though the consensus of the separate tree searches was limited in resolution due to a relatively high degree of homoplasy and probably to rapidly evolving adaptive transformations, phylogenetic hypotheses mostly congruent to recent phylogenetic studies were yielded. These findings are evidence for the usability of cranial soft tissue characters as a reliable additional source of information for cladistic studies of fish phylogeny. With regard to the highly contentious deep splitting events within the Cyprinodontiformes and the monophyly of the Aplocheilidae, the consideration of the new data supported a new hypothesis that agrees with the palaeogeographical framework of the break-up of Gondwana. The genus Aplocheilus from India represents the sister group to all remaining taxa of the Cyprinodontiformes, while the second branch separates the genus Pachypanchax from Madagascar. A comparable biogeographical pattern has been found congruently in different groups of teleostean freshwater fishes. The Valenciidae from Europe are closely related to the Nearctic taxon Funduloidea. The placement of the genus Fluviphylax remained unresolved because it is not only characterized by the possession of several derived characters but also by numerous plesiomorphic ones.