Craugastor rubinus, Jameson & Streicher & Manuelli & Head & Smith, 2022

Jameson, Tom J. M., Streicher, Jeffrey W., Manuelli, Luigi, Head, Jason J. & Smith, Eric N., 2022, Miniaturization in Direct-Developing Frogs from Mexico with the Description of Six New Species, Herpetological Monographs 36 (1), pp. 1-48 : 35-37

Craugastor rubinus sp. nov.

Holotype. — UTA A-62345 (field ID: JAC 30720; Fig. 34A ), male collected by J.W. Streicher, C.L. Cox, C.M. Sheehy, III, R.U. Tovar, and M.J. Ingrasci on the road between Talpa de Allende and El Cuale , Jalisco, Mexico, 20.377078N, 105.047938W, 1771 m, 8 July 2009 .

Paratypes (2). — UTA A- 62347 ( Fig. 34 C ) and MZFC-HE-35616 (formerly UTA A- 62346; Fig. 34 B ), same collection data as holotype .

Diagnosis. —A species of Craugastor distinguished by the following combination of characters: (1) small adult size; (2) reduced ossification of the skeleton in adults relative to other members of series, lacking ossification of any skeletal elements beyond Stage 2 ( Table 3 ); (3) presence of posterolateral projection of frontoparietal; (4) absence of vomerine odontophores; (5) presence of raised tubercles on eyelids; (6) supratympanic fold absent or poorly developed; (7) face flank barred, with snout–nostril–canthal–supratympanic stripe, sometimes broken canthaly and postocularly; (8) one postrictal tubercle; (9) gular region with pale spotting; (10) dorsal surface blotched or unicolored pale; diffuse interorbital bar, small suprascapular spots, sometimes two dark rump spots; (11) middorsal ridge present; (12) dorsum smooth with no tubercles; (13) body flank dark supratympanic stripe extending toward lower midflank, broken, paler toward groin, smooth to finely shagreened; (14) inguinal glands present and axillary glands absent in adults; (15) when leg adpressed to body, heel reaches nostril; (16) outer tarsal ridge with 0–4 extremely small, flat, and round tubercles, no raised fringe; (17) finger and toe pads round, finger tips not or just barely expanded, toe tips slightly lanceolate and barely expanded; (18) inner metatarsal tubercle larger than outer metatarsal tubercle.

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Comparisons. — Craugastor rubinus can be differentiated from C. candelariensis , C. cueyatl , C. hobartsmithi , and C. portilloensis by equal sizes of the inner and outer metatarsal tubercles (unequal sizes in C. rubinus ). It can be differentiated from C. mexicanus , C. montanus , C. omiltemanus , C. polaclavus , and C. saltator by the presence of vomerine odontophores (absent in C. rubinus ). It can be differentiated from C. bitonium and C. pygmaeus by the absence of a posterolateral projection of the frontoparietal (present in C. rubinus ).

Description of holotype. — Holotype small male (SVL ¼ 12.6 mm); snout rounded and short (0.8 mm naris–snout; 7% SVL); short eye–nostril distance (1.3 mm; 10% SVL); tympanum 1.2 mm (9.1% SVL); no supratympanic fold or shoulder tubercle; finger length formula III <IV <II <I; single flat palmar tubercle; single flat prepollical tubercle; subarticular tubercles present on all fingers; supernumerary tubercles not present on hand; right arm removed for genetic analysis; toe length formula IV <III <V <II <I; inner metatarsal tubercle larger than outer metatarsal tubercle; subarticular tubercles present on all toes; supernumerary tubercles present on plantar surface; right leg removed for genetic analysis; small dark supracloacal fold; dorsal color in life included brown and grey mottling, orange coloration on arms extending to posterior edge of tympanum ( Fig. 34A ); venter coloration in life included pale, almost blue speckling similar to other species of C. mexicanus series ( Fig. 35 ); grey in preservative; many bands present on arms and legs.

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Variations in paratypes. —Body sizes (SVL) 10.8 mm (MZFC-HE-35616), 11.5 mm (UTA A-62347); eye–nostril distance both 10% SVL; tympanic ratios both 9%; dorsal color pattern mottled (MZFC-HE-35616; Fig. 34B ) or with dark stripe extending from snout to flank (UTA A-62347, Fig. 34C ).

Distribution. —Known only from the type locality in Jalisco (Talpa de Allende), habitat of pine–oak forest at the southern extent of the Sierra Madre Occidental.

Etymology. —The specific epithet is derived from the Latin rubinus , which means ruby. This name is inspired by the garnet mines found near the type locality of Talpa de Allende in the Sierra Madre Occidental of Jalisco.

Phylogenetics. — Craugastor rubinus was strongly supported as monophyletic in the concatenated analysis (ML ¼ 99; BAYES ¼ 1.0; Fig. 3 ). The new species is also strongly supported as the sister taxon of C. cf. hobartsmithi (ML ¼ 100; BAYES ¼ 1.0). Craugastor rubinus is separated from C. cf. hobartsmithi by a P -distance of 3.4% ( Table 4 ).

Remarks. —The skull of C. rubinus is similar to that of C. hobartsmithi , C. montanus , and C. pygmaeus with more posteriorly placed anterior suture of the frontoparietal and prootic than in other species. The type series was collected from the leaf litter surrounding a mountain stream. The male holotype has slightly pigmented testes. Afemale paratype, UTA A-62345, has large, pigmented ovaries. This species may co-occur with C. hobartsmithi in Jalisco. Despite the small genetic distances separating C. rubinus and C. cf. hobartsmithi , there are many skeletal and morphological differences between these two species, including relative metatarsal tubercle sizes, condition of the posterolateral projection of frontoparietal, and relative snout length ( Table 6 ).

Figures

FIG. 34.—Male holotype of Craugastor rubinus (A, UTA A-62345, SVL ¼ 12.6 mm), male paratype (B, MZFC-HE-35616, SVL ¼ 10.8 mm) and male paratype (C, UTA A-62347, SVL ¼ 11.5 mm). All from Talpa de Allende, Jalisco, Mexico, 1771 m. Leaf litter at the type locality where the specimens were collected (D).

FIG. 35.—Ventral coloration in life from some member of the Craugastor mexicanus series. Craugastor rubinus (A, UTA A-62345); C. pygmaeus (B, UTA A-64284), C. cueyatl (C, UTA A-62348). Note varying levels of bluishwhite speckling. A color version of this figure is available online.

FIG. 3.—Concatenated Maximum Likelihood analyses of two mitochondrial (12S and 16S) and two nuclear (RAG1 and TYR) gene fragments sequenced from the Craugastor mexicanus series (total of 2230 base pairs). Node values correspond to bootstrap support from Maximum Likelihood analysis and posterior probabilities from a Bayesian analysis of the same data set, respectively. Support values are not reported for nodes that had,50/0.50. NS indicates no support in the Bayesian analysis for a depicted relationship. Locality abbreviations are as follows: COL ¼ Colima, HID ¼ Hidalgo, GRO ¼ Guerrero, JAL ¼ Jalisco, MEX ¼ Estado de México, OAX ¼ Oaxaca, PUE ¼ Puebla, and VER ¼ Veracruz.