Limits and relationships of Paracanthopterygii: a molecular framework for evaluating past morphological hypotheses

Gadiforms and percopsiforms have historically been treated as prototypical or core paracanthopterygians. As such, they are the keys to unlocking the evolutionary history and limits of a revised Paracanthopterygii; therefore, we address the taxonomic compositions of gadiforms and percopsiforms and how they are related to each other and other putative basal acanthomorphs. We address these questions by first constructing a phylogenetic hypothesis based on multiple molecular sequences. Both maximum likelihood and parsimony criteria strongly support a Paracanthopterygii comprised of Percopsiformes + [Zeiformes + (Gadiformes + Stylephorus)]. Polymixiids are sister to this clade. Polymixiids + paracanthopterygians are in turn sister to the acanthopterygians (batrachoidiforms, beryciforms, lophiiforms, ophidioids, percomorphs) in the parsimony analysis but sister to Acanthopterygii + Lampriformes (minus Stylephorus) in the likelihood analysis. A review of published morphological characters, putatively pertinent to paracanthopterygian systematics were evaluated by the direct examination of specimens. Results find high congruence between the molecular tree and character-state distributions for many of these internal relationships. New interpretations of homologies of published characters are proposed based on topological and phylogenetic data.