Document Type

Article

Department/Program

Virginia Institute of Marine Science

Publication Date

2000

Journal

American Malacological Bulletin

Volume

15

Issue

2

First Page

179

Last Page

193

Abstract

The Neocoleoidea. sister group to the Bele1nnoidea, includes all li ving cephalopod species except naut.ilids. as well as their imn1ediare ancestors. Several hypotheses have been published about the n1orphology of ancestral neocoleoids. Ancestral states are easily inferred from foss ils for son1e characters, such as 10 anns and the presence of an ink sac in basal coleoids or the presence of fins in ancient octopods. Many inferences are less strongly supported, though. and open to debate. We examine this problen1 using three cladograrns resulting from analyses of morphology and DNA sequences (both rnitochondrial and nuclear) f ron1 san1ples representing the full diversity of extant coleoicls. Character states at three ancestral nodes (neocoleoid. octopodiform. and decapodiform) are reconstructed for 51 1norphological characters using cladistic parsimony. Strong or n1oderate agree1nen1 an1ong the three trees was found for almost 3/4 of the character-at-node reconstructions. The .level of agreen1e11t an1ong the trees varied a1nong nodes, \Vith strongest agree,nent found at the ancestral octopodiform node. Hov,ever. some of these reconstructions eem unlikely to be co1Tect. Changes in subclade resolution can exert vary ing effecLs on inferences about basal nodes. Because several subclade~ 1vi1h in the neocoleoicb are not yet adequaLely resol ved, we cannot be very confi dent in reconstructions of ancestral character states based solely on parsin1ony and \ve propose a provisional suite of character-!state recons1.ruc1.ions in<.:luding other sources of inference in addition to parsi1nony.

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