Idiopyrgus meriadoci, Salvador & Bichuette, 2024

Salvador, Rodrigo Brincalepe & Bichuette, Maria Elina, 2024, Idiopyrgus Pilsbry, 1911 (Gastropoda, Tomichiidae): a relict genus radiating into subterranean environments, Zoosystematics and Evolution 100 (4), pp. 1543-1556 : 1543-1556

Idiopyrgus meriadoci sp. nov.

Fig. 5

Type material.

LES 29798 (holotype), LES 29820 (4 paratypes), MZSP 168420 (2 paratypes). All specimens collected on 10. ix. 2021 (M. E. Bichuette & J. E. Gallão leg.); all paratypes from type locality .

Type locality.

Brazil, Bahia state, Carinhanha municipality, Gruna do Pedro Cassiano (“ Pedro Cassiano Cave ”), 13°47'48.0"S, 43°54'50.0"W.

Etymology.

The species is named in honour of Meriadoc “ Merry ” Brandybuck, from J. R. R. Tolkien’s “ The Lord of the Rings. ” Besides standing with Éowyn against the Witch-king in the Battle of the Pelennor Fields, Merry is also an example of the fight for nature conservation in Middle-earth, pushing the Ents into action and ultimately ending Saruman’s threat to Fangorn Forest.

Diagnosis.

Shell minute, whitish, entirely translucent. Teleoconch sculptured by numerous spiral rows of minute vertical pustulae, arranged roughly equidistantly from one another, which do not form thorn-like periostracal hairs. Aperture oval, adapically and abapically angulated.

Description.

Shell conical, 4 ½ – 4 ¾ whorls, 2.8–2.9 mm high, 1.6–1.8 mm wide. Colour pale yellow to white; shell entirely translucent. Protoconch of 1 ¼ – 1 ½ whorl (transition to teleoconch not easily observable), rounded, smooth (Fig. 5 E, G ). Suture deep. Whorls increasing uniformly in height and width. Teleoconch sculptured by numerous spiral rows of minute vertical pustules, arranged roughly equidistantly from one another (Fig. 5 E, F ); they do not develop thorn-like periostracal hairs as seen in some of its congeners (e. g., I. eowynae sp. nov.), though a few pustules on the body display what seem to be minute truncated hairs in two of the more apically-positioned rows (Fig. 5 F ). Peristome complete, not covering penultimate whorl, expanded, wider in abapical region, narrower in columellar region, of same colour as body whorl. Aperture oval, adapically and abapically angulated, but with smooth, rounded contour. Umbilicus rimate, nearly closed. Operculum oval, paucispiral; corneous, thin, and translucent, of same colour as body whorl. Soft body completely white in colour.

Distribution.

Known only from type locality (Fig. 1 ).

Remarks.

Idiopyrgus meriadoci sp. nov. is easily distinguished from all its congeners by its unique teleoconch sculpture and much smaller shell; it is smaller than even Idiopyrgus minor Salvador, Silva & Bichuette, 2022, which was previously the species with the smallest body size in the genus. The whitish and entirely translucent shell, along with the smaller number of whorls, is likewise useful to easily distinguish it from Idiopyrgus eowynae sp. nov. (see above) and I. umbraticola . The latter two species also display a teleoconch sculpture that seems to be homologous to that of I. meriadoci sp. nov.; the latter, however, lacks the periostracal hairs observed in the former two species.

As for I. eowynae sp. nov. above, there is little variation in shell shape and proportions among the presently available specimens of I. meriadoci sp. nov. (Fig. 5 A – D ).

Figures

Figure 1. Distribution map of Idiopyrgus spp. (and Spiripockia punctata) in caves of the state of Minas Gerais and Bahia, Brazil.

Figure 5. Idiopyrgus meriadoci sp. nov. A, B. Holotype LES 29798; C. Paratype # 1 LES 29820; D. Paratype # 2 LES 29820; E. Detail of the spire of the holotype in apertural view, showing the teleoconch sculpture in the early whorls; F. Detail of the body whorl of holotype in apertural view, showing the teleoconch sculpture; F. Detail of the protoconch of the holotype.