Reconstruction of ancestral character states in neocoleoid cephalopods based on parsimony

The Neocoleoidea, sister group to the Belemnoidea, includes all living ceph alopod species except nautilids, as well as their immediate ancestors. Seve ral hypotheses have been published about the morphology of ancestral neocol eoids. Ancestral states are easily inferred from fossils for some character s, such as 10 arms and the presence of an ink sac in basal coleoids or the presence of fins in ancient octopods. Many inferences are less strongly sup ported, though, and open to debate. We Examine this problem using three cla dograms resulting from analyses of morphology and DNA sequences (both mitoc hondrial and nuclear) from sampler representing the full diversity of erran t coleoids. Character states at three ancestral nodes (neocoleoid, octopodi -form, and decapodiform) are reconstructed for 51 morphological characters using cladistic parsimony. Strong or moderate agreement among the three tre es was found for almost 3/4 of the character-at-node reconstructions. The l evel of agreement among the trees varied among nodes, with strongest agreem ent found at the ancestral oetopodiform node. However. some of these recons tructions seem unlikely to be correct. Changes in subclade resolution can e xert varying effects on inferences about basal nudes. Because several subcl ades within the neocoleoids are not yet adequately resolved, we cannot be v ery confident in reconstructions of ancestral character states based solely on parsimony and we propose a provisional suite of character-state reconst ructions including other sources of inference in addition to parsimony.