Boletín de la Sociedad Geológica Mexicana / 2017 / 199 Two new subfossil species of springsnails (Hydrobiidae: Pyrgulopsis) from North Mexico and their relation with extant species from Cuatrociénegas Alexander Czaja, José Luis Estrada-Rodríguez, Ulises Romero-Méndez, Anselmo Orona-Espino ABSTRACT Alexander Czaja ABSTRACT RESUMEN José Luis Estrada-Rodríguez [email protected] Ulises Romero-Méndez We describe two new species of the Se describen dos nuevas especies del género Anselmo Orona-Espino genus Pyrgulopsis Call and Pilsbry Pyrgulopsis Call and Pilsbry de depósitos Facultad de Ciencias Biológicas, Universidad from subfossil spring deposits of Vi- subfósiles de Viesca, Coahuila, norte de Juárez del Estado de Durango, 35010 Gómez Palacio, Durango, México. esca, Coahuila, in the northern part México. La primera especie, P. paleominc- of Mexico. The first species, P. pa- kleyi sp. nov., tiene conchas trochiformes con leominckleyi sp. nov., has trochiform vueltas planas y hombros bulbosos. Conchas shells with flat whorls and bulbous con características similares posee la especie shoulders. Extant endemic species endémica Pyrgulopsis minckleyi (Taylor), Pyrgulopsis minckleyi (Taylor) displays- originalmente descrita como Nymphophilus similar shell features — this species minckleyi Taylor del complejo de pozas del was originally described as Nympho- valle de Cuatrociénegas, Coahuila. Algunos philus minckleyi Taylor from the spring especímenes de P. paleominckleyi sp. nov. tie- complex of the Cuatrociénegas val- nen hombros en forma de alas, características ley, Coahuila. Some specimens of P. que nunca fueron observadas entre los miem- paleominckleyi sp. nov. show wing-like bros fósiles o recientes del género. Asimismo, shoulders that have never been ob- las conchas de la segunda especie de Viesca, ) from North Mexico served among fossil or extant mem- P. paleoacarinatus sp. nov. son muy simila- bers of the genus. In addition, shells res a P. acarinatus, otra especie endémica de of the second new species from Vi- Pyrgulopsis de Cuatrociénegas. Suponemos esca, P. paleoacarinatus are similar to que los caracoles subfósiles de Viesca son es- Pyrgulopsis P. acarinatus, which is other endemic pecies hermanas o, más probable, precursores Pyrgulopsis species from Cuatrociéne- directos de dos caracoles de manantial recien- gas. We suppose that both sub-fossil tes y endémicos del valle de Cuatrociénegas. springsnails of Viesca are sister spe- cies or, likely, direct precursors of the Palabras clave: Pyrgulopsis, es- two extant endemic springsnails from pecies nuevas, subfósil, Norte de Cuatrociénegas valley. México, Viesca, Cuatrociénegas. Keywords: Pyrgulopsis, new species, sub-fossil, North Mexi- co, Viesca, Cuatrociénegas. BOL. SOC. GEOL. MEX. 2017 VOL. 69 NO. 1 P. 199 ‒ 208 Manuscript received: September 18, 2016 Corrected manuscript received: November 15, 2016 Manuscript accepted: November 20, 2016 Two new subfossil species of springsnails (Hydrobiidae: 200 / Boletín de la Sociedad Geológica Mexicana / 2017 1. Introduction viescaensis Czaja, Estrada-Rodríguez and Rome- ro-Méndez, was described (Czaja et al., 2015). Pyrgulopsis, commonly known as springsnail, is the The spring sediments consist of small travertine INTRODUCTION / MATERIAL AND METHOD most diverse genus of North American freshwa- pieces, shells, shell fragments (debris) and scant ter gastropods and contains approximately 140 remnants of clay. Among the remains of aquatic described species (Hershler et al., 2014; 2016). vegetation, we found oogonia of Chara, seeds of The members of this genus live mostly in springs Nymphaea(?) and endocarps of sedges (Cladium ja- and have a very small geographic distribution maicense Crantz and Schoenoplectus sp.). Microbialite (Hershler and Sada, 2002). Many of the species in (stromatolite) structures in form of tufa limestone western North America, particularly at the Great were observed in both springs. Basin in the northern of Mexico, they are endemic The aim of the present study is to describe the and restricted to small areas or to a single spring. new species of Pyrgulopsis and to show its similari- Hershler et al. (2014) mentioned that members of ties, differences and possible phylogenetic relation the genus prefer emergent macrophytes and hard to related living organisms from Cuatrociénegas substrates as habitat. valley. The oldest occurrence of Pyrgulopsis dates back to the Pliocene (Henderson, 1935) but there is molec- ular evidence that shows the genus colonized the 2. Material and method region of the Lower Colorado River in the late Miocene (Hurt, 2004). There are still no reliable Specimens of the new species were collected from records of fossil Pyrgulopsis shells from Mexico. two recently dried-up springs near the town of Vi- Two shells described by Czaja et al. (2014a, Fig- esca, Coahuila (Figure 1; spring Túnel 4: 25° 20’ ures e and f) as Pyrgulopsis sp. from Late Quaterna- 20” N, 102° 52’ 32” W; spring Túnel 8: 25° 20’ ) from North Mexico ry Paleo-Lake Irritilian Coahuila do not belong to 23” N, 102° 54’ 29” W). Shells of Túnel 4 were this genus but to the sister genus Cincinnatia Pilsbry, collected from a cut inside the spring approx. 50 1891. The only Late Holocene record of Pyrgulop- cm below the surface. Shells of Túnel 8 spring sis, P. manantiali (Hershler), was recently described were collected directly from a narrow fissure, ap- Pyrgulopsis by Czaja et al. (2014b). prox. 60 – 70 cm below the surface. The section is In sediments of two recently dried-up springs near approximately 2 m thick and contains unconsoli- the town of Viesca, Coahuila, specimens of two dated sediments, small travertine pieces and shell species of the genus Pyrgulopsis Call and Pilsbry, debris. Empty shells of the extant species of Pyrgu- 1886 were collected. These shells have morpholog- lopsis minckleyi from Poza Becerra and Poza Azul in ical similarities with shells of two endemic extant Cuatrociénegas (about 200 km away from Viesca) species of Pyrgulopsis from Cuatrociénegas, Coa- were collected during the summer of 2015 directly huila–originally assigned to the genus Nymphophilus from sediments at the bottom of these springs. Taylor. The springs, as called by current research- The sediments were screened through 0.5 mm ers Túnel 4 and Túnel 8, are located at the foot of and 0.3 mm sieves. The shells were photographed small hills in front of the Sierra la Cadena (Figure with a Zeiss AxioCam ERc5s microscope-camera. 1) and they belong to a system of several water Morphometric variables of the shells (shell height bodies that have provided water to small settle- and width, aperture height and width) were mea- ments at the vicinity (Czaja et al., 2015). Both sites sured using a Neubauer Chamber Cell Counting contain an abundance of shells, possibly including Hemocytometer. Shells whorls were counted ac- several new Cochliopidae species (Czaja, unpub- cording to the method of Pilsbry (1939). lished data). Only one of these species, Mexipyrgus The Late Holocene age of the superficial deposits Two new subfossil species of spring snails (Hydrobiidae: Boletín de la Sociedad Geológica Mexicana / 2017 / 201 RESULTS ) from North Mexico Pyrgulopsis Figure 1 Map of the study area with localization of the springs of Viesca. 1= Spring Túnel 4, 2= Spring Túnel 8. from the springs atViesca is confirmed by sever- planned for our next project in Viesca, will give al reports and photographs which document the the exact age). desiccation of the springs during the drought of The material is deposited at the Malacological 1958-1959 (Czaja et al., 2015). According to Late Collection of the Faculty of Biological Science of Pleistocene megafauna bone records at the base the Juarez State University of Durango (UJMC). of the springs (Dr. J. Quiroz, personal data), we estimate the tafocoenosis age for the new species of Pyrgulopsis not older than Late Pleistocene, very 3. Results likely latest Pleistocene/Early Holocene. This is supported also by the excellent conservation of the 3.1. SYSTEMATICS shells which retain often their original shell color- ing (Figure 2a-d; Figure 3a, b, f). Shells of mollusks Family Hydrobiidae Troschel, 1857 of Late Pleistocene sites of the region are always Subfamily Nymphophilinae Taylor, 1966 white bleached (Czaja et al., 2014a) (This dating Genus Pyrgulopsis Call and Pilsbry, 1886 is preliminary, radiometric dating of the shells, Two new subfossil species of springsnails (Hydrobiidae: 202 / Boletín de la Sociedad Geológica Mexicana / 2017 Type species: Pyrgula nevadensis Stearns, 1883, some specimens may be converted to a wing-like by original designation. keel or collar (Figure 2i, j, o). The shells are whit- Pyrgulopsis paleominckleyi Czaja, Estrada-Rodríguez, ish beige to light gray. Operculum not preserved. RESULTS Romero-Méndez and Orona-Espino sp. nov. (Fig- Shell measurements and whorl counts are given in ures 2a, b) Table 1. Types. Holotype, UJMC-270, Túnel 8 Spring, Distribution. Pyrgulopsis paleominckleyi is endemic narrow fissure, approx. 70 cm below the surface to Túnel 8 Spring at Viesca, Coahuila, Mexico. inside the spring, layer approx. 70 – 60 cm below Remarks. Some specimens of P. paleominckleyi the surface, Viesca, Coahuila, Mexico, 25° 20’ 23” show wing-like shoulders on the body-whorls that N, 102° 54’ 29” W. Paratypes from the same lot, have never been observed among fossil or extant UJMC-271-280a, 103 specimens. members of the genus. There are smooth transi- Etymology. The name with the prefix “paleo” tions between shells with weak shoulders and shells suggests that the sub-fossil species is probably an with wing-like shoulder or collar; therefore, we ancestor of the extant species P. minckleyi from Cu- consider that all specimens belong to one single atrociénegas, Coahuila. species. Many other species in Viesca also have a Diagnosis. A small species of Pyrgulopsis, narrow- strong shoulder, often with knobs or spines (Czaja ly umbilicate, ovate-conic to trochiform shell with et al., 2015). We suppose that such feature could penultimate and ultimate whorls flattened. The serve to reinforce the wall of the shell as adaptation new species is differentiated from closely related against predation.