Herpetologica, 57(4), 2001, 515-523 (? 2001 by The Herpetologists' League, Inc. A SEVENTH SPECIES OF MINUTE SALAMANDER (THORIUS: PLETHODONTIDAE) FROM THE SIERRA DE JUAREZ, OAXACA, MEXICO JAMES HANKEN' AND DAVID B. WAKE2 'Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA 2Department of Integrative Biology and Museumiiof Vertebrate Zoology, University of California, Berkeley, CA 94720-3160, USA ABSTRACT: We describe a new terrestrial species of minute lungless salamander of the Mexican genus Thorius (Plethodontidae) from montane pine-oak forests in the Sierra de Juarez of north central Oaxaca, Mexico. The new species is distinguished from congeners by a combination of body size, external morphology, osteology, and dental traits, and it is well differentiated genetically from other named species for which data are available. This is the seventh endemic species of Thornis reported from the Sierra de Juarez, and known localities are geographically isolated from those of all other species. Discovery of another new species of plethodontid salamander from Oaxaca en- hances the state's standing as a preeminent center of herpetological diversity within both M6xico and Mesoamerica. Key words: Miniaturization; Taxonomy; Biogeography; Osteology MESOAMERICAiS one of the world'sbio- comprised only nine formally described diversity hotspots; both the relative and species (Duellman, 1993). In the last sev- absolute numbers of species and the de- eral years, the number of valid, named gree of endemism are exceeded by few species has more than doubled to 22, in- other terrestrial habitats (Myers et al., cluding five new species described from 2000). Approximately 40% of the nearly Oaxaca (Hanken and Wake, 1994, 1998; 3000 species of tetrapod vertebrates re- Hanken et al., 1999). There remain, how- ported from Mesoamerica are endemic to ever, many populations of Thorius that this region, and they represent more than cannot be confidently or easily assigned to 4% of the total number of tetrapod species any known species, and which are believed known worldwide. Within Mesoamerica, to represent undescribed species (Hanken, geographic patterns of species richness 1980, 1983; Hanken and Wake, 1998). vary among taxa. For amphibians and rep- Several of these populations exist at re- tiles, an important center of biological di- mote montane localities in northern and versity is the Mexican state of Oaxaca. In- western Oaxaca, and are poorly represent- deed, the richness of Oaxaca's herpetofau- ed in most museum collections. Here, we na, which includes more than one-third of formally describe a new species of Thorius all species of amphibians and reptiles based on large series of specimens collect- found in Mexico, is exceeded only by Cos- ed from adjacent localities at the extreme ta Rica (Casas-Andreu et al., 1996). northwestern edge of the Sierra de Juairez One of the groups that has helped to of northern Oaxaca (Fig. 1). This species, establish the biological importance of both which is both morphologically and genet- Mesoamerica and Oaxaca is the terrestrial ically distinct from all congeners, further salamander genus Thorius (Plethodonti- enhances Oaxaca's standing as an impor- dae). Thorius is endemic to Mexico, where tant center of herpetological diversity it is restricted to four states along the within both Mexico and Mesoamerica. southeastern edge of the Mexican pla- teau-Oaxaca, Veracruz, Puebla, and MATERIALS AND METHODS Guerrero (Wake and Lynch, 1976). Al- Measurements were made using digital though the genus was first described >130 or dial calipers or a dissecting microscope yr ago (Cope, 1869), as recently as 1993 it fitted with an ocular micrometer; standard 515 516 HERPETOLOGICA [Vol. 57, No. 4 PUEBLA ( OAXACA \,VERACRUZ 11 * schmidti . ttSierra de Huautla o DOmineog A - papaloae @ 67 aureus, boreas, .4'9'> @ arboreus, smithi, 'R, JF insperatus, ; macdougalli 1 ON .]gp < 7-30, 32-45 San Juan del Estado 0 sp. nov. 57,69 ' a B - narisovalis @46 '< FIG. 2.-Photographs of Thorius papaloae. (A) Ho- pulmonaris- 52 lotype, MVZ 183468, an adult female. Photo by D. 0 Wake. (B) Live specimen, collected at the type lo- Oaxaca Mexico cality by J. Hanken and H. B. Shaffer, 15 February 1976 (museum number unavailable). Photo by J. 40 km Hanken. Scale bars = 0.5 cm. 97' 96'30 FIG. 1.-Map of north-central Oaxaca, M6xico, showing the type localities (closed circles, bracket) of see Wake and Elias (1983) for comparisons Thorius papaloae and its geographically closest con- with other tropical genera. Counts of pre- geners. Thorius papaloae is known from several lo- sacral (trunk) vertebrae do not include the calities near the village of Concepcion Papalo. All lie within montane pine-oak forest at elevations ranging first, or atlas, vertebra. Except for the ho- between 2500 and 2850 m. The open circle denotes lotype, tooth counts are based on cleared- the locality of two sympatric populations of Thorius and-stained specimens; all alcoholic spec- from 15 km northeast of the village of San Juan del imens were examined for the presence of Estado, 2550 m elevation. Neither of these popula- teeth. Numbers of vomerine tions can be referred to any named species; each like- maxillary ly represents an additional, undescribed species. Lo- teeth in the holotype are provided sepa- cation of main map area in southeastern M6xico is rately for right and left sides; these counts depicted in inset at lower right. Populations are num- are summed for other individuals. Insti- bered according to Hanken (1983). tutional abbreviations are as listed in Lev- iton et al. (1985) except for MZFC (Museo length (SL) was measured from the ante- de Zoologfia, Facultad de Ciencias, Univ- rior tip of the snout to the posterior angle ersidad Nacional Autonoma de Mdxico, of the vent. Limb interval equals the num- M exico, D. F.). ber of costal interspaces between the tips DESCRIPTION OF NEW SPECIES of appressed fore- and hind limbs, mea- sured in one-half increments (e.g., 3, 4.5). Thorius papaloae sp. nov. Whole-mount skeletal preparations were Paipalo Minute Salamander stained for bone and cartilage using aliza- Holotype.-MVZ 183468, an adult fe- rin red S and Alcian blue 8GX, respective- male from 8 km (road) NE of Concepci6-n ly (Klymkowskyand Hanken, 1991). Os- Paipalo, Gaxaca, Medxico,elevation 2670 m,- teological descriptions use the cranial collected 15 February 1976 by J. Hanken character states and mesopodial patterns and H. B. Shaffer (Fig. 2A). described and illustrated by Hanken Paratypes.-All from Oaxaca, Medxico: (1982, 1984, 1985), Hanken and Wake MVZ 183470, 183473, 183475, 187052-69 (1994, 1998), and Hanken et al. (1999); (18 specimens), same data as the holotype; December 2001j HERPETOLOGICA 517 MVZ 183479, 183483, 183485-6 (two beyond the margin of the jaw in dorsal specimens), 183493-94 (two specimens), view. A suborbital groove intersects the lip 183496, 183504-5 (two specimens), on each side of the head. There are 1-2 183508, 183510, MCZ A-134202-3 (two premaxillary teeth in adult males (mean specimens), MZFC 12630-31 (two speci- 1.8) and 0-5 teeth in females (mean 2.2). mens), same data as the holotype, except There are no maxillary teeth. Vomerine 11 km (road) NE of Concepcion Papalo, teeth average 6.1 in both males (range 4- elevation 2820 m; MVZ 183518, same data 10) and females (4-8). Limbs are moder- as the holotype, except 15 km (road) NE ately long; limb interval averages 3.6 in of Concepcion Paipalo, elevation 2850 m; males (range 3-4) and 4.5 in females (4- LACM 121728-29 (two specimens), 6). Hands and feet are relatively well de- 121731, 121733, 121737-38 (two speci- veloped and moderately broad; foot width mens), approximately 14 mi E of Santos averages 1.0 in males (0.9-1.1) and 1.1 in Reyes Paipalo (likely identified incorrectly, females (0.9-1.2). Digits 1 and 4 (hand) should instead be Concepcion Papalo- and 1 and 5 (foot) are short, but the cen- see Remarks), elevation 2500 m, collected tral digits are relatively long and have 3 August 1975 by T. W Taylor and A. D. rounded tips. Fingers, in order of decreas- Lau. Some specimens are cleared and ing length, are 3-2-4-1; toes are 3-2-4-5-1. stained or have had tissue removed for The tail is moderately long (exceeds stan- protein comparisons. dard length) and tapered; mean SL divid- Diagnosis.-This is a small species of ed by tail length equals 0.85 in two males Thorius with large, elliptical nostrils, no (range 0.83-0.86) and 0.92 in six females maxillary teeth, and a relatively long tail (0.75-1.06). A round and relatively prom- (Fig. 2B). Most specimens have prominent inent mental gland is present in most adult paratoid glands. It is distinguished from all males (maximum dimensions: 1.2 mm other small species of Thorius from the Si- wide, 1.0 mm long). The postiliac gland is erra de Juairez that lack maxillary teeth, as small and pale, and it is relatively incon- follows: from T macdougalli in having spicuous externally in some adults. Para- somewhat larger hands and feet, a slightly toid glands are prominent in most speci- narrower head, more vomerine teeth, and mens, but less so in a few others. premaxillary teeth in most females, and in This is a relatively dark species, with lacking a mottled dorsal coloration; from some indication of an obscure dorsal band T insperatus by having narrower, more in most individuals. Specimens with the elongate nostrils; from T arboreus in hav- lightest band have a herringbone pattern ing larger adult size, a larger, more elon- middorsally. The venter, while dark, is gate nostril, and a more obscure dorsal lighter than the flanks, and the underside coloration; and from T pulmonaris in hav- of the tail is especially light.