Landouria Godwin-Austen, 1918

Nurinsiyah, Ayu Savitri, Neiber, Marco T. & Hausdorf, Bernhard, 2019, Revision of the land snail genus Landouria Godwin-Austen, 1918 (Gastropoda, Camaenidae) from Java, European Journal of Taxonomy 526, pp. 1-73 : 9-10

Genus Landouria Godwin-Austen, 1918

Landouria Godwin-Austen, 1918: 604 (type species by original designation: Helix huttonii Pfeiffer, 1842 (new name for Helix orbicula Hutton & Benson, 1838 , not H. orbicula Orbigny, 1835 )).

Thaitropis Schileyko, 2004: 1632 , fig. 2104 (type species by original designation: Helix goniochila Pfeiffer, 1862 (= Helix ptychostyla Martens, 1860 ; see Schileyko 2011)).

Remarks

Schileyko & Kuznetsov (1998) pointed out that the features of Landouria correspond to those of Aegista with the exception of the lack of a dart apparatus. Furthermore, they supposed that the dart apparatus might have been lost several times within the Aegistini , once in the Indian lineage and once in the lineage of the species from the Indo-Australian Archipelago and the Philippines. They argued that this hypothesis is also supported by the different structure of the flagellum, which bears external tubercles in the continental lineage but is indented in the Archipelagic lineage. The molecular phylogeny of Hirano et al. (2014) showed that the dart apparatus was actually lost at least three times within the Aegistini and other studies have shown that the loss of the dart apparatus is also a common homoplasy in other groups of the Helicoidea ( Neubert 1998, 2014; Wade et al. 2007; Neiber & Hausdorf 2015; Neiber et al. 2017). However, the molecular phylogeny of Köhler et al. (in press) showed that the species of Landouria from the Sunda Islands form a clade with L. omphalostoma Páll-Gergely & Hunyadi, 2013 from China. The structure of the flagellum is variable in the species from the Asian mainland ( Schileyko & Kuznetsov 1998; Páll-Gergely et al. 2013) as well as in those from the Indo-Australian Archipelago (see Köhler et al. in press and results below). Thus, there is no reason to assume an independent loss of the dart apparatus in the continental and Archipelagic lineages.

Hirano et al. (2014) showed that Landouria is the sister taxon of a group of high-spired species from the Ryukyu Islands and Taiwan, which were formerly erroneously included in the Chinese Pseudobuliminus Gredler, 1887 , which also lack a dart apparatus. Thus, the loss of the dart apparatus is probably a synapomorphy of this group and Landouria . Landouria differs from this group in the depressed conical or globular shell, which usually has periostracal scales or hairs. However, these character states are plesiomorphies that Landouria shares, e.g., with Aegista . Currently, no morphological apomorphies of Landouria are known.

Schileyko (2004) separated two species from Thailand in a distinct genus, Thaitropis . He considered a sharp constriction between the epiphallus and penis as the main diagnostic character of Thaitropis . We also found a similar constriction in L. pacitanensis sp. nov. and in a less drastic form in L. intumescens ( Martens, 1867) and L. smimensis ( Mousson, 1848) from Java. There is a verge in the dilatation proximal of the constriction in L. pacitanensis sp. nov. Thus, the constriction is not situated between the epiphallus and penis, but within the penis. Schileyko did not find a verge, but there is also a small dilatation proximal of the constriction in the Thai species figured by Schileyko. Thus, we suppose that the constriction is also within the penis in the Thai species. As long as the phylogenetic relationships within Landouria are not better resolved and the genus is not further subdivided, we consider Thaitropis to be a synonym of Landouria . However, it is possible that the Southeast Asian species and the Himalayan species, to which the type species of Landouria , L. huttonii ( Pfeiffer, 1842) , belongs, form separate clades that might be classified at least as subgenera. In this case the name Thaitropis would be available for the Southeast Asian clade.

In the following, the species are ordered according to similarities to facilitate comparisons.