The phylogeny and classification of Scaphopoda (Mollusca): an assessment of current resolution and cladistic reanalysis

Abstract

Reynolds, P. D. 1997. The phylogeny and classification of Scaphopoda (Mollusca): an assessment of current resolution and cladistic reanalysis.-Zool. Scr. 26; 13-2 1.The first cladistic analysis of phylogeny in the class Scaphopoda (Steiner 1992a(Steiner ,1996 examined relationships among family and selected sub-family taxa using morphological data. A preferred/ consensus tree of relationships illustrated monophyly of the orders Dentaliida and Gadilida, partial resolution among dentaliid families, and complete resolution among gadilid taxa. However, several alternative replications of the analysis, including use of a revised data matrix, did not produce the reported tree number or level of resolution; in all cases, monophyly of the Dentaliida was not supported by strict consensus of resultant parsimonious trees. Reanalysis, using unordered characters and outgroup rooting, only clearly resolves monophyly of the Gadilida and the sister relationship of the Entalinidae with the remaining gadilid families. These analyses emphasize the need for more comparative data and thorough parsimony analysis in scaphopod cladistic phylogenetics, as relationships in this class are still some way from resolution.

Point of View Phylogeny of Scaphopoda (Mollusca) in the light of new anatomical data on the Gadilinidae and some Problematica, and a reply to Reynolds

“…Moreover, outgroups allow no conclusion in regard to the plesiomorphic state. Reynolds (1997) does not agree with Steiner (1992b) on the longitudinally sculptured shell being plesiomorphic. He makes an effort to prove that fossils in the form of siliceous replicas can show very fine shell sculpture.…”

“…The basis of this phylogenetic analysis is the character matrix of Steiner (1992b) corrected by Reynolds (1997). Important additional information on soft part morphology comes from serial sections of 11 species of genera previously unavailable for light microscopical studies.…”

“…Referring to Steiner (1992b) and Reynolds (1997), most characters with character states are only briefly described here. Again, if not stated otherwise, shell and radula data are taken from Emerson (1962), Palmer (1974 and Scarabino (1979Scarabino ( , 1986aScarabino ( ,b, 1995, anatomical data come from Steiner (1990Steiner ( , 1991Steiner ( , 1992a and from this study.…”

“…The heuristic search option was applied with 100 replicates of random addition sequence, TBR and/or SPR branchswapping, MULPARS option, zero-length branches collapse, and multistate taxa interpreted as polymorphism. Reynolds (1997) obviously used the default setting of PAUP treating multistate taxa as uncertainties. This has profound influence on tree lengths.…”

Muscle development in Antalis entalis (Mollusca, Scaphopoda) and its significance for scaphopod relationships

“…The question whether the dentaliidan muscularhydrostat system or the gadilidan combined muscular retraction vs. hydraulic expansion system represents the basal scaphopod condition remains unsolved, also because scaphopod phylogeny as a whole is still unclear (Steiner, 1992b(Steiner, , 1996Reynolds, 1997;Reynolds and Okusu, 1999). …”