ANALYSIS OF MORPHOLOGY TO DETERMINE PRIMARY SISTER-TAXON RELATIONSHIPS WITHIN COLEOID CEPHALOPODS

Although most families of living coleoid cephalopods are well defined, phylogenetic relationships among them are controversial. A necessary first step toward analyzing the phylogeny of decapod families is the d etermination of proper outgroups to polarize characters. The cladistic position of the Vampyromorpha is of particular interest. Toward this goal, we have examined 50 morphological characters in 24 species from 17 families. The material examined included representatives from the o egopsids, myopsids, sepioids and sepiolids, cirrate and incirrate octo pods, and Vampyroteuthis. At this level, the characters were polarized either by comparison with Nautilus, or, for a few, by ontogenetic seq uence or the fossil record. We found that of these 50 characters, 25 c ould not be used with confidence because of problems primarily involvi ng character independence, apomorphic ''loss,'' or assessment of homol ogy/homoplasy. The states of three characters could be assumed to be o rdered. Only ten characters were unambiguously informative as defining synapomorphies at the ordinal level. The resulting consensus of most- parsimonious trees is: (((oegopsid + myopsid + sepioid + sepiolid)(((c irrate)(incirrate)) vampire))(nautilus)).