CLADISTIC-ANALYSIS OF THE OCTOPODS BASED ON ANATOMICAL CHARACTERS

Parsimony analysis of 29 finned and finless octopod taxa considered 66 anatomical and morphological characters to discover synapomorphies th at unite monophyletic groups. The resultant cladogram (177 equally par simonious trees at 191 steps, CI 0.429) resolved all relationships exc ept those among the 16 exemplars of the Octopodidae included and those among Tremoctopus, Ocythoe and Argonauta. Bootstrap values of over 90 % support the monophyly of the finned and finless octopods, relationsh ips among the finned octopods, the bolitaenids and the monophyly of Ha liphron, Tremoctopus, Ocythoe and Argonauta; bootstrap values for othe r nodes range from 57 to 79%. Among finned octopods, specimens represe nting Grimpoteuthis are basal, as Voss (1988a) suggested. Specimens of Opisthoteuthis represent a distinct lineage, and are sister taxon, in this analysis, of Cirroteuthis (although specimens of Stauroteuthis c ould not be included). New definitions of the genera Opisthoteuthis an d Grimpoteuthis are provided to reflect their separate evolutionary hi stories rather than their overt morphological similarity. Among finles s octopods, bolitaenids are basal. The monophyletic Octopodidae is the sister taxon to the clade containing the sister taxa Vitreledonella a nd Amphitretus, and Haliphron, Tremoctopus, Ocythoe and Argonauta. The Ctenoglossa and Heteroglossa, families grouped by shared radular dent ition, are diphyletic and paraphyletic, respectively. The cladistic re lationships demonstrate that both the Vitreledonellidae and Idioctopod idae are junior synonyms of the Amphitretidae; despite conspicuous mor phological differences separating these taxa, they share a recent evol utionary history.