Towards a complete classification of the Neotropical thorny catfishes (Siluriformes: Doradidae)

We propose a revised classification of Doradidae based on phylogenetic analyses of sequence data for one nuclear (rag1) and two mitochondrial (co1, 16s) genes, and corroborated by caudal-fin morphology. The molecular dataset comprises 174 doradid specimens representing all 31 valid genera, 83 of the 96 valid extant species and 17 species-level taxa that remain undescribed or nominally unassigned. Parsimony and Bayesian analyses of molecular data support six major lineages of doradids assigned here to three nominal subfamilies (Astrodoradinae, Doradinae, Wertheimerinae) and three new ones (Acanthodoradinae, Agamyxinae, Rhinodoradinae). The maximum parsimony topology of Doradidae was sensitive to ingroup density and outgroup age. With the exceptions of Astrodoradinae and Doradinae, each subfamily is diagnosed by caudal-fin characteristics. The highest degree of fusion among skeletal elements supporting the caudal fin is observed in Acanthodoradinae and Aspredinidae, lineages that are sister to the remaining doradids and aspredinoids (i.e., Auchenipteridae + Doradidae), respectively. Fusion among caudal-fin elements tends to be higher in taxa with rounded, truncate or emarginate tails and such taxa typically occupy shallow, lentic habitats with ample structure. Caudal-fin elements are more separated in taxa with moderately to deeply forked tails that occupy lotic habitats in medium to large river channels.