Helicoidea

Abstract: The present paper provides a complete overview of the camaenid land snail fauna of the 22 largest islands along the Kimberley coast, northwesternmost Western Australia, which were surveyed between 2007 and 2010. These islands were found to harbour a total of 104 species (83 new) in 15 genera (5 new), including taxa described recently. Species were essentially delimited by means of comparative analyses of shells (size, shape, sculpture, colouration), genital anatomy (in particular penial anatomy), and genetic differentiation in a mitochondrial marker (partial 16S rRNA sequences). Additionally, the radular and jaw morphology of selected species was studied but found to provide little useful information for taxonomic purposes. Species of the following genera are treated: Amplirhagada Iredale, 1933 (22 species), Carinotrachia Solem, 1985 (2 subspecies), Kimberieymelon Kohler, 2010 (1 species), Kimberleydiscus Kohler, 2010 (1 species), Australocosmica Kohler, 2011 (6 species), Kimboraga Iredale, 1939 ...

Abstract: Molecular phylogenetic relationships among 45 members of the Helicoidea (Gastropoda: Stylommatophora) were examined using partial mitochondrial 16S rRNA sequences. Phylogenetic relationships were inferred using maximum parsimony, maximum likelihood and Bayesian methods. The reconstructed phylogenies showed a good degree of support for more recent branches, but gave little support to deeper nodes. Mitochondrial rDNA data further confirmed monophyletic status of helicids, recognized monachine hygromiid and bradybaenid clades and resolved a number of relationships in the helicelline hygromiids. With the respect to the latter assemblage, most of the anatomically based groups are confirmed, corroborating the diagnostic value of the dart-sac complex and a close affinity between Ichnusomunda sacchii and species of the genus Cernuella. Nevertheless, some well resolved branches challenge previous systematic arrangements, grouping species previously placed in different arrangements. In particular, support was not found for the monophyly of helicelline hygromiids with pedal penial innervation. Possible explanations for these incongruencies are suggested. 16S sequence data are appropriate for studies of relationships within the different species groups and less so for recovery of more ancient radiations in the Helicoidea. It will be valuable to combine the 16S data with other gene sequences to estimate basal relationships. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85, 501–512.