Abstract

The evolutionary relationship of three species belonging to the genus Cornuspiroides is inferred using four species of Cornuspira and the monotypic genus Cornuspirella as an outgroup. All known morphological features of the test are coded as independent characters (synapomorphies) and their evolutionary relationship is inferred using parsimony. The genus Cornuspiroides appears as a monophyletic group on the resulting evolutionary trees, although evidential support is weak (54%). The species Cornuspiroides striolatus and Cornuspiroides rotundus are endemics of the shallow and cold waters of the Arctic and the Antarctic seas, respectively. These two endemic species are found to share an immediate common ancestry, although support is low (61%). The closest relative of the two polar species is inferred to be the little known Cornuspiroides profundum, which has been found living in the cold and shallow waters of the Arctic and also the temperate waters of the North Atlantic. Limitations of available data preclude C. profundum from being designated as their actual ancestor. The current classificatory groups of Cornuspiroidinae, Cornuspira, and Cornuspirinae appear as artificial paraphyletic groups on the inferred tree and have no significant evidential support of characters.

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