MICROSCULPTURES OF CONVERGENT AND DIVERGENT POLYGYRID LAND-SNAIL SHELLS

Polygyrid evolution has produced five pairs of closely convergent shel l forms, four of which occur in sympatry. Scanning electron microscopy of the apertural parietal and basal denticles (or regions) (at about 500x) in those ten species, and of the body whorl (at about 100x) in t hose and eleven more polygyrid species, reveals possible new microscul ptural characters, homologies, and radiations. Twelve informative new character states are tentatively proposed, of which half support, with out homoplasy, previous shell-free phylogenetic hypotheses based on an atomy and allozymes. Two of the homoplastic characters actually enhanc e shell-form convergences, which are nonetheless distinguishable using other microsculptural features. Further SEM studies are warranted to test these proposed characters, to add others, and to test the hypothe sis that shell micromorphology is much more informative than shell mac romorphology for land-snail phylogenetics.