Taxonomic revision of two endemic land snail genera from the Top End of Northern Australia with remarks on two problematic species named by de Férussac and Le Guillou (Eupulmonata, Camaenidae)

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Abstract

Parglogenia Iredale, 1938 and Arnemelassa Iredale, 1938 are two poorly known genera from the Top End of the Northern Territory that are characterised by highly similar shell features. Both genus names were introduced by reference to the exclusively shellbased descriptions of their type species. In addition, further nominal species taxa have previously been referred to Parglogenia in species lists without assessment of their morphology. For the lack of additional morphological information and in the absence of comparative analyses of key morphological features, these taxonomic arrangements were in need of critical evaluation. Here, key morphological characters of Arnemelassa and Parglogenia, including features of the genital anatomy, are being described and their taxonomy is being revised based on comparative analyses of these features. Both genera are characterised by peculiar and quite distinct features of their genitalia while having highly similar, likely convergent shells. The only species within Arnemelassa, its type A. creedi, occurs in the eastern part of the Top End. In Parglogenia, the type species P. pelodes is also recognised as its only member. For this species a neotype is designated in order to stabilize its complicated taxonomy. Other nominal species associated with this genus are removed from the genus Parglogenia for not exhibiting features deemed to be typical for this genus. Taxonomic placement of these species, Helix prunum Ferussac, 1821 and Helix subgranosa Le Guillou, 1842, is currently uncertain and they are listed under Incertae Sedis within the Camaenidae.