GRIFFITHS, O.L. 2001. A new snail of La Reunion. Bull. Phaethon, 13 : 54.

Publié le par Jean-Michel PROBST

Bulletin Phaethon, 13 : 54.

A new land snail of La Réunion
Gulella argoudi

Owen Lee Griffiths*

*Bioculture Ltd., Senneville, Rivière des Anguilles, île Maurice

Résumé : Depuis 10 ans, 14 espèces nouvelles ont été décrites dans les Mascareignes. Une espèce nouvelle de Streptaxidae, endémique de La Réunion, est décrite ici : Gulella argoudi (Griffiths, 2000). Cette espèce a été nommée d’après le nom du co-découvreur, Jean Jacques Argoud, professeur à La Réunion.

Matériel type

Holotype : Subfossil adult shell, buried 10 cm deep in dry soil under basaltic rock overhang on edge of ravine cutting the old part of Chemin Bruniquel, E. of La Saline Les Bains, Réunion, at 250 m. 21°4.8’S ; 55°15.8’E, coll. O.L. Griffiths, C. Stevanovitch et J.J. Argoud, Déc. 1992 (AMS C202876).

Paratypes : One adult and one subadult shell from the type locality, (AMS C202862).

Description

Shell cylindrical, 5 whorls, with conical apex. Protoconch faintly maleated. Rest of shell with strong closely spaced, wavy, slightly oblique costulae. Aperture rounded at base. Lip thickened, well reflected. Upper part of aperture with a thickened short parietal lamina, almost meeting a blunt labral denticle about half way down labrum, which corresponds to a small external pit. Upper part of columellar has small flat process inside aperture. Umbilicus slit like in adults, rounded and faintly perforate in juveniles.

Dimensions of Holotype
Height : 3.7 mm ;
Diameter : 1.8 mm.

Remarks

The strong costulate sculpture combined with the distinctive apertural dentition seperates this readily from all other Mascarene straptaxids. However the features of the shell are characteristic of the Gulella infans group of outhern Africa (Dr van Bruggen pers. comm. 1995). According to Dr van Bruggen “in the case of Réunion, occurrence of a species of the Gulella infans group widely distributed in southern Africa is at least remote thus we might surmise a shared ancestry of both species”. G. argoudi is distinguished from the South African members of the G. infans group by its smaller size – 3.7mm vs 4.8-6.7mm high for members of the G. infans group (from Connolly, M. 1939). The whorls of G. argoudi are also more rounded. This species is thus readily distinguished from G. infans. G. argoudi forms a completely new element in the Mascarene streptaxid fauna and represents a separate, much more recent and unradiated invasion. Althought described from subfossil specimens, the presence of a Gulella shell fragment (possibly belonging to this species) collected in leaflitter at Cap Noire, Dos d’Ane Réunion, at 1300m, in 1992, suggests this species may still survive.

Bibliographie

GRIFFITHS, O.L. 2000. Nine new species of Mascarene land snails (Mollusca : Gastropoda). Molluscan Research 20 (2) : 37-50.

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