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Two new populations of Pyrgulopsis were found in springs in the Chihuahuan desert region of Texas. Pyrgulopsis Call & Pilsbry, 1886 are a diverse group of snails occupying freshwater springs, usually narrow-range endemics limited to a single spring. Their small ranges confer substantial conservation concern as the drying or disturbance of a single spring can lead to their extinction. We use mitochondrial COI and nuclear LSU sequences, shell morphometrics, and anatomical features to distinguish a new species of Pyrgulopsis endemic to the Big Bend region of Texas.

Pyrgulopsis Call Pilsbry, 1886 is a genus of small (<5 mm) spring snails, usually endemic to single freshwater springs. Two new populations of Pyrgulopsis found in very small, isolated springs and spring runs in the mainstem Rio Grande watershed of western Texas are distinguished from congeners. Mitochondrial and nuclear sequences, morphometrics, and morphological characteristics support Pyrgulopsis rubra sp. nov. and Pyrgulopsis harrymilleri sp. nov. as distinct from other known Pyrgulopsis species, including the geographically proximate P. metcalfi.

There are eight described species in Phreatodrobia, minute, phreatic (subterranean aquatic) snails, all stygobitic and endemic to the Edwards-Trinity Aquifer System of Texas. Two species were described from river drift (Pilsbry Ferriss 1906) and the others more recently by sampling the water flowing from wells or springs (Hershler Longley 1986b; Hershler Longley 1987). Recent sampling from spring orifices and the hyporheic zone of streams have extended the known ranges of the phreatic snails of the region and encountered unknown snails (Alvear et al. 2020). Here we describe Phreatodrobia spica n. sp., a rarely encountered species with a large range of about 400 km (Figure 1). We find P. spica in samples with a diverse assemblage of phreatic animals including other species of Phreatodrobia, isopods, amphipods, coleopterans, and mites. Phreatodrobia spica is distinguished from congeners using morphological and molecular evidence and is characterized by an elevated, trochiform shell with unique sculpture that include spikes and pustules. It has an open umbilicus and a complete, reflected lip that is sometimes appressed to the body whorl.