Habeastrum omphalium, Simone, 2019

Simone, Luiz Ricardo L., 2019, The new genus Habeastrum, with two new species (Gastropoda, Diplommatinidae) in Mato Grosso do Sul caves, Brazil, Zootaxa 4543 (2), pp. 287-290 : 288

Habeastrum omphalium new species ( Figures 1 K–R)

urn:lsid:zoobank.org:act:524FD91C-2855-40F8-8419-747E459DB3D1

Types. Holotype MZSP 135583 ( Figs 1 K–N) . Paratypes: MZSP 134324 , 8 shells all from type locality .

Type locality. BRAZIL. Mato Grosso do Sul, Bonito, Gruta Pitangueiras , 21°06’37”S 56°34’52”W (Trajano & Gnaspini col., 16.vii.1992) .

Diagnosis. Shell with about 5 whorls growing uniformly widely. Umbilicus wide.

Description. Shell relatively trochiform, conical. Total of about 5 whorls, uniformly widening, spire angle about 50° to 60° ( Figs 1 L–P). Protoconch 0.42 mm wide, smooth, except for minute radial wrinkles, translucent ( Figs 1O, Q ); occupying about 35% of shell width, about 20% of shell length. Shell varying from wide ( Figs 1 L–N) to very wide ( Figs 1O, P ). Teleoconch sculpture as for genus ( Fig. 1Q ), with about 75 axial cords on penultimate whorl. Suture deep, whorl profile rounded. Aperture rounded, not deviating from whorl profile, slightly orthocline ( Fig. 1M ); minimally deformed by penultimate whorl; occupying about 42% of shell width, about 25% of shell length. Umbilicus deep, wide, occupying about 20% of inferior shell area ( Figs 1K, R ).

Distribution. Known only from the type locality, possibly endemic.

Habitat. In soil in caves (no living specimen found).

Measurements (length and width in mm). Holotype: 1.6 mm by 1.1 mm ( Figs 1 K–N); Paratypes MZSP 134324, #2, 1.0 mm by 0.9 mm ( Fig. 1O ); #3, 1.0 mm by 0.9 mm ( Fig. 1P ).

Etymology. The specific epithet refers to wide umbilicus, result of the wider growth of the shell, from the Greek omphalos.

Taxonomic discussion. Habeastrum parafusum can be distinguished from H. omphalium by the characters described above. The main difference is the degree of inflation during the shell growth, much larger in H. omphalium than that of H. parafusum . This difference produces, in specimens of a same size, shells with different shape (rather cylindrical in H. parafusum and conical in H. omphalium ), different number of whorls (about 7 in H. parafusum , 5 in H. omphalium ), and distinct umbilicus width (wider in H. omphalium ). Despite having been found in the same cave, the relatively large amount of specimens and the lack of intermediates between both shell shapes ensure the species’ distinction.

Figures

FIGURE 1. Habeastrum spp. shells. A–J. Habeastrum parafusum, n. sp. A. Holotype MZSP 134301, L 1.4 mm. B–J. Paratypes MZSP 135584, L 1.7 mm. C. L 1.6 mm. D. L 1.6 mm. E. L 1.4 mm. F. SEM, L 1.1 mm. G. L. 1.2 mm. H. same specimen, showing protoconch and first teleoconch whorls, SEM, scale = 0.1 mm. I. same specimen of F, scale = 0.1 mm. J. Young specimen, L 0.6 mm. K–R. H. omphalium n. sp. K–N. Holotype MZSP 135583, W 1.1 mm, L 1.6 mm. O–R. Paratypes MZSP 134324. O. L 1.0 mm. P. SEM, L 1.0 mm. Q–R. Scale = 0.1 mm.