Rhinus gilbertus, Simone, Luiz Ricardo L. & Casati, Rafael, 2013

Simone, Luiz Ricardo L. & Casati, Rafael, 2013, New land mollusk fauna from Serra da Capivara, Piauí, Brazil, with a new genus and five new species (Gastropoda: Orthalicoidea, Streptaxidae, Subulinidae), Zootaxa 3683 (2), pp. 145-158 : 153-154

Rhinus gilbertus new species

( Figs. 23–34 )

Types. Holotype MZSP 112449 ( Figs. 24–28 ). Paratypes MZSP 111827, 27 shells (sta. P2), MZSP 111835, 98 shells (sta. P2), MZSP 111839, 50 shells (sta. P2), MZSP 111844, 9 shells (sta. P1) ( Figs. 30–31 ), MZSP 111845, 9 shells ( Figs. 32–33 ), USNM, 2 shells; MNRJ, 2 shells. All from type locality.

Type locality. BRAZIL. Piauí; Serra da Capivara ; Coronel José Dias municipality, close to Sítio do Mocó town, Cave Toca de Cima dos Pilão, 8°51’47.10”S 42°33’26.96”W (R. Casati col, 2012).

Diagnosis. Shell somewhat elongated, with width/length ratio of ~40%. Axial undulations relatively strong, almost forming sculpture. Peristome occupying ~30% of shell length, strongly deflected. Umbilicus opened, narrow.

Description. Shell of about 20 mm. Color pure white to pale brown. Periostracum not preserved. Outline somewhat turriform to bulimuloid; width ~40% of length. Protoconch of 1.5 whorls, opaque, obese, suture wellmarked; sculptured by delicate, uniform, undulating striae ( Figs. 23 , 29 ); occupying ~5% of shell length and ~25% of shell width; border protoconch-teleoconch clear, slightly prosocline (angle ~10° with longitudinal axis) ( Figs. 28, 31, 33 ). Spire of ~6 rounded whorls, tall, being wider in penultimate whorl; angle ~50° ( Figs. 24–26, 29, 30– 33 ); suture well-marked. Sculpture uniform series of axial, narrow undulations, from suture to suture, ~ 60 in penultimate whorl; interspaces between undulations equivalent to their width. Body whorl equal ( Figs. 30, 31 ) to ~5% narrower ( Figs. 24, 26, 32, 33 ) than preceding whorl. Peristome deflected outwards, expanding ~10% width of preceding whorl; aperture orthocline ( Figs. 25, 31, 33 ). Aperture elliptical, occupying ~30% of shell length and ~50% of width ( Figs. 24, 30, 32 ); lacking teeth; outer lip rounded, with middle region slightly straight; inner lip highly concave, superior half almost straight, inferior half also almost straight and wide, as tube surrounding umbilicus; low, blunt columellar carina somewhat distinct ( Fig. 25 ). Callus thin, planar, simple, narrowly attached to penultimate whorl ( Figs. 24, 25, 30, 32 ). Umbilicus opened, narrow, partially occluded by inner lip ( Fig. 27, 34 ).

Measurements (in mm): Holotype MZSP 112449: 21.9 by 8.3 ( Figs. 24–28 ); paratypes: 111844 ( Figs. 30–31 ): 18.7 by 7.5; MZSP 111845 ( Figs. 32–33 ): 18.7 by 8.1.

Distribution. Only known from type locality.

Habitat. Caatinga semi-dry environment; collected inside caves.

Material examined. Types. Non-type material from type locality MZSP: 112347, 10 shells, 112356, 10 shells, 112357, 9 shells, 112367, 4 shells, 112368, 7 shells, 112373, 7 shells, 112399, 15 shells, 112415, 25 shells, 112420, 15 shells, 112432, 40 shells, 112437, 20 shells, 112442, 18 shells.

Etymology. The specific epithet refers to the father of junior author, Gilberto Casati, who provided financial support and encouragement from his academic affairs.

Systematic remarks. The main character of the genus Rhinus is the hairy periostracum, a character that cannot be seen in the examined material, composed of mostly long dead shells. However, the resemblance of R. gilbertus with several species of this genus suggests the generic attribute. Another character suggestive of the genus is the striated protoconch ( Figs. 23 , 29 ). Only few of the Rhinus that have elongated shell; most has a more globose shape. The elongated-shaped Rhinus ( Simone, 2006) , R. gilbertus resembles R. constrictus (Pfeiffer, 1841) , from NE Brazil, differing in being more slender (width/length ratio of ~40%, against ~62% of that species); it also resembles R. evelinae Leme, 1986 , from São Paulo, and R. obeliscus Haas, 1936 , from Santa Catarina. It differs in having a slightly more rounded outline, as that two species are still more elongated (ratio of both species ~35%), and two fewer whorls. R. gilbertus is the most elongated Rhinus from the NE Brazil, as elongated shape is more common in SE Brazilian species. A young specimen is shown in Fig. 29 , displaying a different shape.

Figures

FIGURES 16 – 23. Type shells. Figs. 16 – 22: Cyclodontina capivara n. sp. shell of types; Fig. 16, holotype MZSP 112448, apertural view (L 19.2 mm); Fig. 17, same, right view; Fig. 18, same, dorsal view; Fig. 19, paratype MZSP 111845 – 1, apertural view (L 20.4 mm); Fig. 30, same, # 2 (L 17.0 mm); Fig. 21, paratype MZSP 111837, young specimen, apertural view (L 6.5 mm); Fig. 22, same, detail of apex in profile (W 2.0 mm); Fig. 23, Rhinus gilbertus n. sp., holotype, detail of apex in profile (W 1.5 mm).

FIGURES 24 – 34. Rhinus gilbertus n. sp. type shells. Figs. 24 – 28, holotype MZSP 112449 (L 21.9 mm); Fig. 24, apertural view; Fig. 25, right view; Fig. 26, dorsal view; Fig. 27 anterior-slightly left view; Fig. 28, apical view; Fig. 29, paratype MZSP 111827, young specimen, apertural view (L 13.9 mm); Fig. 30, paratype MZSP 111844, apertural view (L 18.7 mm); Fig. 31, same, dorsal view; Fig. 32, paratype MZSP 111845, apertural view (L 18.7 mm); Fig. 33, same, dorsal view; Fig. 34, same, detail of last whorl with umbilicus.