, Volume 456, Issue 1-3, pp 165-174

Can we infer heteronemertean phylogeny from available morphological data?

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Abstract

This study uses morphological data from the primary literature to make a first pass at a cladistic analysis of the order Heteronemertea, which includes about one-third of the accepted species of the phylum Nemertea. This produced numerous trees and almost completely unresolved consensus trees. We conclude that this stems from imprecise and inadequate taxonomic descriptions of species and their morphological features, resulting in a limited number of characters and extensive homoplasy. The analyses neither support previously proposed ad hoc hypotheses of internal grouping nor do they propose robust new hypotheses. Rather, the analyses indicate that morphology-based cladistic studies of heteronemerteans will require very extensive, critical comparative study of heteronemertean morphological features. Re-examination of type material and common species appears to be the most fruitful approach to developing a clade-based classification of heteronemerteans.