Chilonopsis Fischer von Waldheim, 1848

Gerlach, Justin, Griffiths, Owen, Hume, Julian P., Louchart, Antoine, Sorrel, Philippe & Cairns-Wicks, Rebecca, 2025, Diversity of the extinct land snail genus Chilonopsis of St Helena (Mollusca: Gastropoda: Achatinidae), European Journal of Taxonomy 1007, pp. 176-210 : 184

Genus Chilonopsis Fischer von Waldheim, 1848

Chilonopsis Fischer von Waldheim, 1848: 236 .

Nesobia Ancey, 1887: 39 .

Cleostyla Dall, 1896: 419 .

Helenopachnodus Germain, 1931: 169 .

Type species

Chilonopsis sulcata Fischer von Waldheim, 1848: 236 , by original designation (= Chilonopsis aurisvulpina ( Holten, 1802)) .

Diagnosis

Shells ovately conical to narrowly elongate; thin to moderately thick; whorls moderately convex, sometimes shouldered; protoconch with fine spiral striae of variable prominence; teleoconch sculpture of spiral and radial striae, intersecting to produce a scalloped or waved effect; suture sometimes raised into bosses of variable prominence. Lip usually only slightly expanded, not thickened; umbilicus closed or nearly so; aperture subvertical, ovate; columella obliquely truncate to subtruncate, often with a ridge or nodule.

Remarks

The larger St Helena snails were recognised as a separate genus, Chilonopsis by Fischer von Waldheim in 1848. The genus was placed in the Achatinidae by Fischer (1883) (as the ‘Stenogyridae’) and further supported by Pilsbry (in Dall 1896) based on the form of the jaw and radula. Schileyko (1998) placed one species ( Chilonopsis helena ( Quoy & Gaimard, 1832) , as Nesobia helena ) in the Pachnodidae Steenberg, 1925 without explanation. He placed the other species (as Chilonopsis and Cleostyla ) in the Petriolinae of the Subulinidae P. Fischer & Crosse, 1877 ( Schileyko 1999). Subulinidae , along with Petriolinae , are now regarded as being within the Achatinidae ( Bouchet et al. 2017) . Similarly, Petit & Coan (2008) did not explain their listing of one species ( Chilonopsis aurisvulpina ) under Ferussaciidae Bourguignat, 1883 . As all species share similar aspects of sculpture they are considered all to belong to the same family.

Dall (1896) and Pilsbry (1904) listed two subgenera: Chilonopsis (Chilonopsis) for species possessing sutural bosses ( C. aurisvulpina , C. melanioides , C. subplicatus ) and Chilonopsis (Cleostyla) for more elongate species lacking bosses. These were treated as separate genera by Schileyko (1999) but given that the development of the bosses is variable and C. aurisvulpina appears more similar to C. helena in all features other than the bosses than to the other ‘ Cleostyle ’ species, we consider them to be artificial groupings and retain all species in Chilonopsis .