Phreatoviesca spinosa Czaja & Gladstone, 2021

Czaja 1, Alexander, Gladstone 2, Nicholas S., Becerra-Lopez 1, Jorge Luis, Estrada-Rodriguez 1, Jose Luis, SaenzMata 1, Jorge & Hernandez-Teran 3, Fernando, 2021, A remarkable new genus and species of subterranean freshwater snail from a recently dried-up spring of Viesca, Coahuila, Northern Mexico, Subterranean Biology 39, pp. 129-141 : 129

publication ID

https://dx.doi.org/10.3897/subtbiol.39.67799

publication LSID

lsid:zoobank.org:pub:7C135129-340D-49D4-8BBD-DD8C9AD3C358

persistent identifier

https://treatment.plazi.org/id/C72889DC-5B7A-4366-B703-964353942786

taxon LSID

lsid:zoobank.org:act:C72889DC-5B7A-4366-B703-964353942786

treatment provided by

Subterranean Biology by Pensoft

scientific name

Phreatoviesca spinosa Czaja & Gladstone
status

sp. nov.

Phreatoviesca spinosa Czaja & Gladstone sp. nov.

Figs 2-13 View Figures 2–13 , 14-17 View Figures 14–17 , 18-24 View Figures 18–24

Type locality.

Mexico, Coahuila state, Viesca , spring “Túnel 7" (25°20'38"N, 102°54'19"W, 1102 m a.s.l.) (Fig. 1 View Figure 1 ).

Types.

Holotype (Figs 2 View Figures 2–13 , 3 View Figures 2–13 ), UJMC 500, from type locality, leg. A. Czaja, 15/v/2019. Paratypes, UJMC 501-511, from same lot, >100 dry shells.

Etymology.

Name is derived from the Latin word Phreatoviesca spinosa = having spines.

Referred material.

Coahuila. Viesca , Spring “Túnel 7", UJMC 500-511, A. Czaja, J. L. Estrada-Rodríguez 10/vi/2015 and 15/v/2019.

Diagnosis.

Like for the genus.

Description.

Shell small, conical, white or colorless, sometime with rests of light brown periostracum, yielding diversity in shell form, with 4- 5½ rounded whorls (usually 5), whorls increasing in radius, the first three whorls never uncoiled, subsequent whorls open coiled, body whorl always uncoiled, some specimens show a ‘corkscrew’ -like morphology (Figs 3 View Figures 2–13 , 6 View Figures 2–13 ), suture deep; teleoconch sculptured with irregular, strong marked growth lines and with ribs (Figs 4 View Figures 2–13 , 5 View Figures 2–13 ), spiny shells with whorls with a peripheral slightly pronounced carinae, ribs at the carina are modified into regularly spaced shovel-shaped spines (Figs 14 View Figures 14–17 , 24 View Figures 18–24 ), transition protoconch/teleoconch distinct, marked by a change in surface texture from pitted to axial growth lines, whorls rapidly increasing in diameter, first two whorls smooth, without carina or spines, the last three whorls with increasing number spines (up to 40 on the body whorl, but usually less than 30), spiral lines beginning at the end of protoconch, a few specimens with smooth whorls without any sculpture but with thickened axial growth lines, some (smooth) specimens with a varix just behind the aperture (Fig. 13 View Figures 2–13 ), body whorl large, apertures large, ovate to subrounded, often trumpet-like (Fig. 9 View Figures 2–13 ). Protoconch with coarsely honeycomb-like pits, the basal and outer lip rounded and thin, some smooth specimens with trumpet-like peristome, umbiculus deep or, in corkscrew-like specimens, almost without umbiculus; Opercula not preserved. Shell measurements (mean ± standard deviation in parentheses; n = 17): SH 2.08 (0.31) mm, SW 1.24 (0.17) mm, AH 0.79 (0.09) mm, AW 0.61 (0.08) mm, WN 4.93 (0.44) whorls; HBW 1.23 (0.21) mm. Paratypes from the type locality.

Measurements of holotype.

WN 5¼ whorls; SH 2.26 mm; SW 1.41 mm; AH 0.86 mm; AW 0.67 mm, HBW 1.46 mm.

Habitat.

The new species was found exclusively in one spring near Viesca , Coahuila. The original habitat was probably the outlet of a cave, were the species likely inhabited interstitial waters.

Distribution.

A microendemic species, only in spring “Túnel 7", near the town of Viesca .

Remarks.

The open coiled last whorl, shovel-shaped spines and a protoconch with coarsely honeycomb-like pits are the most evident characteristics which differentiated the shells of Phreatoviesca gen. nov. et. sp. nov. from shells of all other described stygobiotic gastropods in North America. We considered these shell features as derived characters (apomorphy) of a new clade, most likely within the family Cochliopidae . The SEM imagines of the two different morphotypes (smooth and spinous) from Viesca show that both have identical coarsely honeycomb-like pitted protoconchs (Figs 18 View Figures 18–24 , 19 View Figures 18–24 ) and also the details of the shell wall microstructure with fine growth lines are similar (Figs 22 View Figures 18–24 , 23 View Figures 18–24 ). Therefore, we consider these two morphotypes as belonging to the same species. There is no significant difference in shells measurements between smooth and spiny morphotypes and therefore sexual dimorphism is unlikely. Moreover, most of the shells have strong spines and only less than 5% of the morphotypes collected are smooth. Two morphotypes (one smooth and other with lamelliform costae) not associated with sexual dimorphism, were reported also from shells of the subterranean genus Paludiscala Taylor, 1966, described from the neighboring Cuatro Ciénegas Basin (Hershler, 1985). Interestingly, our material is conchologically similar to members of the stygobiotic and stygophilic genus Pyrgophorus Ancey, 1888 in Mexico, which show similar shovel-shaped spines ( Grego et al. 2019). This resemblance is surely an evolutionary convergence and result from living in subterranean habitats.