Comparative osteology and phylogenetic systematics of fossil and living bony-tongue fishes (Actinopterygii, Teleostei, Osteoglossomorpha)

Several recent studies using analyses of morphological characters have addressed the interrelationships of Osteoglossomorpha, a group that sometimes is considered the living sister group of all other living teleosts. Many characters used in these studies were found to be poorly defined, to be coded incorrectly or illogically, or to display more variation than was described. The goal of this study is to address these concerns and contribute generally to knowledge of the morphology and systematic relationships of osteoglossomorphs. Analysis of 72 characters (65 informative) scored for 20 genera resulted in two most parsimonious cladograms (171 steps, CI = 0.6433, CI = 0.6139 excluding uninformative characters, HI = 0.3977, HI = 0.3861 excluding uninformative characters; RI = 0.7782; RC = 0.5006). Osteoglossomorpha is supported by both synapomorphies and homoplasies, although its monophyly was not truly tested in this analysis (only a single outgroup, Elops , was included in the analysis). The only difference in the topologies of these cladograms is in the position of ?Lycoptera (recovered as either the sister group of all other osteoglossomorphs sampled or of ?Eohiodon +Hiodon ). ?Ostariostoma is recovered as the sister group of all non‐hiodontiform osteoglossomorphs. Mormyrids are the sister group of notopterids + osteoglossids. This clade has not been found in other recent analyses. Mormyrids and notopterids usually are considered more closely related to each other than to any other group; characters not included here support this relationship and future consideration of these characters must be made. Although almost completely dichotomous, many nodes of the resulting trees lack rigorous support. For example, ?Palaeonotopterus is interpreted as the sister group of all mormyrids sampled, although for this taxon only 22% of characters could be scored. © 2003 The Linnean Society of London. Zoological Journal of the Linnean Society , 2003, 137 , 1?100.