Balconorbis coronae ( Hershler, 1987 ), 2025

Perez, Kathryn E., Saenz, Vanessa, Guerrero, Yamileth, Gonzalez, Lisa, Guerrero, Evan, Diaz, Pete, Hutchins, Benjamin T. & Schwartz, Benjamin F., 2025, New and revised groundwater snails (Mollusca, Caenogastropoda, Cochliopidae) from karst and associated hyporheic habitats in western Texas and northern Mexico, Subterranean Biology 50, pp. 119-151 : 119-151

Balconorbis coronae ( Hershler, 1987) comb. nov.

Figs 4 F , 5 I

Phreatodrobia coronae Hershler, 1987, pp. 133–139 .

Phreatodrobia coronae Alvear et al., 2020 , pp. 7, fig. 6.

Types.

Holotype USNM 859219 .

Type locality.

USA, Texas, Val Verde County, unnamed spring (now named Indian Springs Canyon Springs) on E side of Devils River in canyon (named Indian Springs Canyon) just downflow from Slaughter Bend, Devils River.

Material examined.

All sites are in Texas, USA. Val Verde County • Lake Amistad National Recreation Area, Indian Springs Canyon Springs, Devils River , drift net sample, collected by K. E. Perez, C. Ortega, R. Chastain (29.6582, - 100.91765), 8 December 2020, ( ABC -000886 ) .

Additional material examined.

– Val Verde County • Indian Springs (29.66383, - 100.9275), 6 December 2020, K. E. Perez, C. Ortega, R. Chastain, ( ABC -000881 ) ; • San Felipe Creek , drift net sample, (29.36887, - 100.88388), 6 December 2020, B. Schwartz ( USNM 1571292 ) ; • Blue Hole, Finegan Springs, Devils River (29.8938, - 100.99456), B. Schwartz ( USNM 1571290 ) ; • Finegan Springs, Devils River , (29.900708, - 100.998476), ( USNM 1571291 ) ; • Snake Spring (29.896319, - 100.981214), B. Schwartz ( ABC -000915 ) ; • Boiling Trough Spring (29.6402, - 100.92647), J. Gordon, M. Turner, R. Hoffman ( ABC -000917 ; • Finegan 105, (29.9048, - 101.01111381), Devils River , Pete Diaz, ( ABC -000922 ) ; • Blue Hole , (29.893872, - 100.99453), 19 March 2013, Randy Gibson, ( ABC -000923 ) .

Description.

Shell minute, transparent and colorless. Near-planispiral to depressed-trochoid. Deeply impressed sutures. First whorl of protoconch uncoiled to a horn-like apex, sculptured with wrinkled pits. Teleoconch sculpture with strong raised spiral lines near protoconch, and later with both raised spiral and longitudinal lines. On some specimens, collabral ribs (costae) are strongly defined while absent or very faint in others. If present, ribs start on the penultimate whorl and increase in size towards the body aperture. Widely open umbilicus, aperture circular to ovate depending on overall shell shape (planispiral to trochoid). Peristome flared all around and tilted adapically.

Taxonomic remarks.

Phreatodrobia coronae was assigned to Phreatodrobia based on a similar shell outline to P. micra ( Pilsbry & Ferriss, 1906) and P. nugax ( Pilsbry & Ferriss, 1906) (depressed to sub-trochoid), however, both mitochondrial and nuclear data consistently place P. coronae outside Phreatodrobia , with strong support. Phreatodrobia coronae displays dimorphism in several features, an aspect not common among Phreatodrobia , and has a distinctive, uncoiled protoconch, also not found among other Phreatodrobia species. We have considered whether this species should be reassigned to Balconorbis based on the DNA sequence relationship. This relationship is weak, and different genes and analysis parameters affect the placement of both Balconorbis uvaldensis and Phreatodrobia coronae . These two genes are insufficient to fully resolve the backbone of the tree of the Cochliopidae . The average divergence in COI between Balconorbis uvaldensis and P. coronae was 18.5 %, slightly above the average divergence among genera overall (17.2 %) and the 3 rd position of the COI locus was saturated at this level, making the relationship in the LSU phylogeny more reliable. The LSU phylogeny places P. coronae with Balconorbis , but this is far from certain.

In the ETAS and nearby aquifers, there are members of the cochliopid fauna with depressed or subtrochoid shells that are also known only from shell or shell + anatomical descriptions and not represented in our phylogeny (e. g., Coahuilix and Phreatomascogos ). We compare some key features of these species in Table 2 . Coahuilix is diagnosed by raised riblets on the teleoconch, a flared aperture, and a flat, incised spire. In contrast, B. coronae lack all these features. Phreatomascogos has prominent keels, an unraised spire, a campanulate operculum, and a relatively closed umbilicus. In contrast, B. coronae is unkeeled, has a raised spire, a round operculum, and an umbilicus that is the width of several whorls.

Although our evidence is inconclusive about whether P. coronae is a member of Balconorbis or a new genus, it seems more conservative to move the species to Balconorbis rather than erecting a new genus at this time. Lacking strong support in the phylogeny and DNA sequences of Balconorbis sabinasensis and other Mexican taxa, the affinity of this species is not fully resolved. It is clear though that it is not a member of Phreatodrobia . We propose the new combination Balconorbis coronae comb. nov. with the understanding that the inclusion of more resolved DNA data and more thorough sampling of the region, especially in Mexico, will likely shed additional light on these relationships in the future.

Ecology and habitat.

Habitat and associated fauna for Balconorbis coronae localities is similar to Texapyrgus diaboli , as they are found in many of the same springs in the Devils River watershed. Balconorbis coronae was collected from spring drift net samples with water chemistry values ranging from 15.06–23.28 ° C, pH 6.49–7.4, conductivity of 366.3–608.8 μS / cm, and dissolved oxygen of 4.33–8.47 mg / L.

Figures

Figure 4. SEM of shells A shells of Stygopyrgus variabilis sp. nov., Las Palmas 5, Lower Canyons of the Rio Grande, Brewster Co., TX. ANSP 506748 B Las Palmas 1, Lower Canyons of the Rio Grande, Brewster Co., TX C shell of Stygopyrgus gracilis sp. nov., Fresno Creek, Fresno Canyon, Presidio County, TX. ANSP 506744 D Texapyrgus diaboli, comb. nov., lectotype of Tryonia diaboli, ANSP 91726, Drift of Devils River, Val Verde County, TX E Big Satan Canyon, Devils River, Val Verde County, TX F Phreatodrobia embossa sp. nov., Caroline Springs, Terrell County, TX. ANSP 506746. Scale bars: 500 µm (A – C, F); 300 µm (D, E).

Figure 5. SEM of protoconch sculpture A – D & teleoconch sculpture E – I A, E Stygopyrgus variabilis sp. nov. Individual from Las Palmas 1, Lower Canyons of the Rio Grande, Brewster County, TX B, F Stygopyrgus gracilis sp. nov. Individual from Fresno Canyon, Presidio County, TX C, G Texapyrgus diaboli comb. nov. Individual from Big Satan Canyon, Devils River, Val Verde County, TX D, H Phreatodrobia embossa sp. nov. Individual from Caroline Springs, Terrell County, TX I Balconorbis coronae comb. nov. Individual from Indian Springs Canyon Springs, Val Verde County, TX. Scale bars: 100 µm (A – E); 50 µm (E – I).