Results of character optimization analysis using an alternative morphology-based phylogeny. Phylogeny redrawn from Mo , based on 126 morphological characters. Red branches indicate venomous lineages, black branches indicate non venomous lineages, and yellow branches indicate groups not examined in this study. As in Figs. 4 and 6, the independent evolution of venom glands is indicated in the Loricarioidei (sensu  and ), in the family Callichthyidae. Patterns of venom gland evolution in the Siluroidei are obscured, due to the poor resolution of basal relationships. Given the broad range of siluroid families in which venom glands are found and similarities in venom composition between these families, a single, relatively basal development of venom glands seems the most parsimonious and likely scenario.
Wright BMC Evolutionary Biology 2009 9:282 doi:10.1186/1471-2148-9-282