Chiropterotriton infernalis

Description of the holotype. Moderately sized adult male (SVL 39.3) with short trunk and very long (TL / SVL 1.32), thin tapering rounded tail. Large, wide head (HW / HL 0.61) with protruding eyes that extend just beyond margin of jaw when viewed from above. Nostril small (NL 0.23), oval shaped (NL / NW 1.44). Head flattened (head depth 2.7), snout blunt, nasolabial protuberances well developed. Oval-shaped mental gland present. Premaxillary teeth (3) pierce lip, vomerine teeth (21) arranged in a row extending nearly to outer margin of choanae. Very long limbs (LI - 2), hands and feet very large and wide (FW 5.0) and webbed, with terminal and part of penultimate phalanges of third toe extending out of webbing on the hand and foot. Toe tips rounded with very well developed subterminal pads. Digits in order of increasing length: manus I-II ~ IV-III, pes I-V ~ II-IV-III. Phalangeal formulae: manus 1 - 2 - 3 - 2, pes 1 - 2 - 3 - 3 - 2. Measurements (in mm), limb interval and tooth counts of the holotype. SVL 39.3, TL 51.9, AX 20.4, HL 10.1, HW 6.2, head depth at posterior angle of jaw 2.7, snout projection beyond mandible 0.4, IO 2.2, EN 1.7, IN 2.0, eyelid length 2.8, eyelid width 1.4, horizontal orbit diameter 2.1, FLL 11.6, HLL 12.9, snout to forelimb 13.1, width of right hand 3.8, FW 5.0, T 3 1.5, T 5 1.4, snout to anterior angle of vent 37.6, tail width at base 2.1, tail depth at base 2.5, shoulder width 4.6. NL 0.23, NW 0.16. Adpressed limbs overlap by 2 costal folds. Premaxillary teeth 3, maxillary teeth 53, vomerine teeth 21. Variation: The three largest individuals in the type series are approximately the same size (38.0 – 41.6 mm) and are sexually mature, suggesting that this may be near the maximum size for males of the species. The only female paratype is substantially smaller than the holotype (SVL 29.7 mm), but the maximum size of females is likely equal to or larger than that of the holotype. Compared to the holotype, the limbs of the rest of the type series are relatively shorter, with the largest limb interval (relatively shortest limbs) equal to 1 costal fold of separation between adpressed limbs. Counts of maxillary and vomerine teeth vary substantially within this species; the largest male paratype (UMMZ 111325, SVL 41.6 mm) has only 36 premaxillary-maxillary teeth. Coloration of the holotype in life (from photos). Upper side of head and dorsum from rostrum to insertion of forelimbs Pratt’s Rufous (72) with scattered Clay Color (20) speckles, slightly lighter from snout to interocular region. Dorsum Sepia (286) with Smoke Gray (266) speckles. Upper side of tail Fawn Color (258) with Tawny Olive (17) speckles. Upper side of limbs Mahogany Red (34) with Medium Chrome Orange (75) mottling. Upper side of hands and feet Medium Fawn Color (256) with Smoky White (261) flecks. Toe tips Dark Rose (238). Gular region and underside of limbs Flesh Ocher (57), venter Dusky Brown (285) with scattered pale flecks. Underside of tail Sepia (279). Iris Yellow Ocher (14). Coloration of the holotype in alcohol. Dorsum medium brown with pale flecks, becoming more numerous on head. Lighter brown on sides of head and from snout to interorbital region. Dorsal surface of limbs grey-brown with pale yellowish mottling, upper surface of feet greyish. Ventral surface greyish very pale yellow, with some very pale yellow mottling on gular region. Underside of feet light grey. Habitat and distribution. All specimens of this species have been found in caves of the Sistema Purificación, the longest known cave system in Mexico. The two specimens for which we have detailed collecting information (the holotype and IBH 29575) were collected inside caves fairly near to the entrances. The habitat around the caves consists of mixed pine, oak, and Liquidambar forest with limestone rock outcrops containing small caves or crevices. The Sistema Purificación remains relatively poorly explored for salamanders, and the species doubtless occurs in many caves in the region of the type locality. Although the type series and all referred specimens are from Tamaulipas, the type locality is less than 2 km from the border with Nuevo León, and the species almost certainly occurs in that state as well. T. Burkhardt (pers. comm.) found salamanders that we tentatively assign to this species to be abundant in a cave in Nuevo León east of Zaragoza, suggesting that it occurs somewhat more widely in the region. Both Aquiloeurycea galeanae and A. scandens occur at the type locality of C. infernalis.

Diagnosis. Assigned to Chiropterotriton based on presence of sublingual fold, extensively webbed feet, long tail, and mtDNA sequence data analysis. Distinguished from all other species of Chiropterotriton except C. magnipes and C. mosaueri by relative size of feet for males (FW / SVL C. infernalis males 0.115 ± 0.011, female 0.092 vs. C. cieloensis males 0.098 ± 0.0093, females 0.098 ± 0.118; C. cracens males 0.087 ± 0.0064, females 0.090 ± 0.014; C. miquihuanus males 0.072 ± 0.0069, females 0.073 ± 0.0075; C. multidentatus males 0.107 ± 0.0076, females 0.101 ± 0.013; C. priscus males 0.084 ± 0.0068, females 0.084 ± 0.0064). Distinguished from C. magnipes by less extensive foot webbing (webbing reaches onto penultimate phalange in C. infernalis vs. all digits fully within web for C. magnipes), fewer premaxillary / maxillary and vomerine teeth (MT males: C. infernalis 49.3 ± 7.11 vs C. magnipes 79.1 ± 5.59; females: C. infernalis 53 vs. C. magnipes 93.6 ± 22.14; VT males: C. infernalis 17.6 ± 3.16 vs.

Etymology. The specific epithet, Latin for infernal, hellish, or lower, makes reference to the cave-dwelling subterranean habits of this species. The incredible extent of the Sistema Purificación cave system, parts of which remain unexplored, gives the sensation of entering into the underworld when searching for salamanders at localities such as the Cueva del Brinco.

Holotype. MVZ 269665 (original field number SMR 2033), an adult male from the Cueva del Brinco, Conrado Castillo, ca. 43.5 km SW (by rd) of Ejido Guayabas, Municipio Hidalgo, Tamaulipas, Mexico, 23.95949 ° N, 99.47447 ° W (WGS 84 datum), 1920 m elevation, collected 11 October 2012 by Sean M. Rovito, Mariana Meneses Marín and Rafael Barzalobre Gerónimo. Paratypes. 8 specimens, all from the Sistema Purificación, Tamaulipas, Mexico. Seven males: KU 182340, Sumidero de Oyamel; KU 182341, Viento Bajo; KU 182342, Pozo de Juan Fuentes Pérez, Conrado Castillo; KU 187773, Cueva X, Conrado Castillo; KU 187776, Cueva del Moro, Yerbabuena; UMMZ 111325 – 111326, El Chihue, 17 km by road SE of Revillagigedo, ca. 1890 m elevation (6200 ft). One female: KU 187774, Cueva X, Conrado Castillo. Referred specimens. IBH 29575, KU 182338, 182339, UMMZ 111323, 111324, 111327.