Laotia Saurin, 1953

Genus Laotia Saurin, 1953 View in CoL

( Fig. 13C View Figure 13 )

Laotia Saurin, 1953: 113–114 View in CoL .

Tope species: Laotia pahiensis Saurin, 1953 View in CoL (by monotypy).

Content: Tree species: Laotia christahemmenae Páll-Gergely, 2014 ( Páll-Gergely 2014), Laotia luongi Páll-Gergely & Hunyadi, 2021 , and Laotia pahiensis Saurin, 1953 ( Saurin 1953; also Fig. 13C View Figure 13 ).

Distribution: Northern Vietnam and northern Laos.

Remarks: Te molecular phylogenetic analysis ( Fig. 9 View Figure 9 ) revealed that Laotia forms a strongly supported clade with many species and genera of Diplommatinidae and represents a separate lineage within that clade with an unresolved basal node. Owing to the uncertainty regarding the phylogenetic relationships between Laotia and (other) Diplommatinidae , we erect a new subfamily for Laotia and Messageria within Diplommatinidae , instead of erecting a new family in its own right. Even if the Diplommatinidae comprise two strongly supported subclades ( Webster et al. 2012, Köhler 2023; Fig. 9 View Figure 9 ), we lack molecular information on the majority of diplommatinid genera (currently 35 genera, of which 8 are fossil-only; MolluscaBase 2024), and predicting the systematic position of each genus would be very difficult based on morphological characters alone. Terefore, we leave all other Diplommatinidae without classifying them into subfamilies.

Te shell shape of Laotia is strikingly similar to that of the extinct (Miocene–Cretaceous) European genus Ferussina Grateloup, 1827 (type species: Ferussina anostomaeformis Grateloup, 1827 , by monotypy) (Supporting Information, Fig. S6E View Figure 6 ), which is currently classified in its own subfamily in the Cyclophoridae ( Páll-Gergely and Neubauer 2020, Páll-Gergely et al. 2023) [previously in its own family, Ferussinidae Wenz, 1923 ( 1923 –1930); see Bouchet et al. 2017]. Te similarity could result either from relatedness or from parallel/convergent evolution. Te former hypothesis can be tested by searching for inner tubes in Ferussina similar to the ones found in Laotia shells. We examined a sample containing ~230 shells (O-Oligozän, Landschneckenkalk, Hochheim-Flörsheim, coll. Kinkelin) in the SMF. Two shells had a broken last whorl, which presented the opportunity to investigate the presence or absence of inner gas-exchange chambers. Given that no such chambers were found, we consider the similarity between Laotia and Ferussina to be a result of parallel/convergent evolution.