Craugastor polaclavus, 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 : 32-33

Craugastor polaclavus sp. nov.

Holotype. — UTA A-62392 (field ID: JAC 21230; Fig. 31 ), female collected by E.N. Smith and colleagues in Portillo del Rayo , Distrito San Pedro Pochutla, Sierra Madre del Sur , Oaxaca, Mexico, 15.973038N, 96.997118W, 1550–1585 m, 24 September 2001 .

Paratypes (4). — UTA A- 55246, a recent hatchling collected by E. N. Smith and José Luís Camarillo Rangel from Río Salado, Sierra Madre del Sur, Oaxaca, Mexico, 16.1941678N, 97.09758W, 1245 m, 26 September 1997 . UTA A- 66098 and MZFC-HE-35582–83, adult or subadult specimens all collected with the holotype .

Referred specimen (1). — UTA A- 66097, female, same data as holotype.

Diagnosis. —A species of Craugastor distinguished by the following combination of characters: (1) small adult size (maximum SVL ¼ 14.7 mm); (2) highly reduced ossification of skeleton in adults relative to other members of series; (3) presence of posterolateral projection of the 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 no distinctive canthal stripe, 1–2 particularly dark bars below eye; (8) one or two postrictal tubercles; (9) gular region with pale spotting; (10) dorsal surface blotched; suprascapular chevron, interorbital bar; (11) pale or as background middorsal ridge; (12) dorsum smooth with only large scattered tubercles; (13) body flank darker anteriorly, no sharp delineation of color change, smooth to 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 expanded, toe tips slightly expanded; (18) inner metatarsal tubercle larger than outer metatarsal tubercle.

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Comparisons. — Craugastor polaclavus can be differentiated from C. candelariensis , C. mexicanus , C. montanus , C. omiltemanus , and C. saltator by the presence of vomerine odontophores (absent in C. polaclavus ). It can be differentiated from C. bitonium , and C. cueyatl by the condition of adpressed leg where the heel does not reach the nostril (reaches nostril in C. polaclavus ). It can be differentiated from C. hobartsmithi and C. pygmaeus by the absence of a posterolateral projection of the frontoparietal (present in C. polaclavus ). It can be differentiated from C. portilloensis by metatarsal tubercles of equal size (unequal in C. polaclavus ). It can be differentiated from C. rubinus by relative finger lengths of IV ¼ II (IV> II in C. polaclavus ).

Description of holotype. — Holotype small female (SVL ¼ 14.7 mm); snout rounded and short (0.8 mm naris–snout; 5% SVL); short eye–nostril distance (1.4 mm; 7% SVL); tympanum 1.4 mm (10% SVL); mild supratympanic fold terminating in small shoulder tubercle; finger length formula III <IV ¼ II <I; single palmar tubercle; single prepollical tubercle; subarticular tubercles present on all fingers; supernumerary tubercles not present on hand; 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; small supracloacal fold; dark supratympanic fold in life with orange shoulder tubercle ( Fig. 25 ), shoulder tubercle color not visible in preservative; many bands present on arms and legs; left leg removed for genetic analysis.

Variations in paratypes. —Body sizes in SVL 8.2 mm (UTA A-55246), 12.3 mm (UTA A-66098), 11.6 mm (MZFC-HE-35582), 13.5 mm (MZFC-HE-35583); eye–nostril distance 11–13% SVL; tympanic ratios 7–8%.

Distribution. —Intermediate elevations in the foothills of the Sierra Madre del Sur in Oaxaca 1245–1585 m ( Fig. 7 ). These habitats consist of mixed tropical dry and temperate sierra forests.

Etymology. —The specific epithet is a combination of the Latin pola meaning small and clavus meaning wart. The name is an allusion to the small size and rugose appearance of several individuals in the type series.

Phylogenetics. — Craugastor polaclavus was inferred to be the sister taxon of C. candelariensis with strong support in the concatenated analysis (90 ML; 0.99 BAYES; Fig. 3 ) and nDNA-only analysis (ML> 90, BAYES> 0.90; Fig. 5 ). The placement of C. polaclavus was less certain in the mtDNA, where it was found to be the sister taxon of a clade containing C. cf. hobartsmithi þ C. rubinus (ML ¼ 51, BAYES ¼ 0.74; Fig. 4 ). In terms of genetic distances ( Table 4 ), C. polaclavus was most similar to C. portilloensis (5.8%), followed by similarity to C. bitonium (5.9%).

Remarks. —The skull of C. polaclavus is similar to C. mexicanus , C. omiltemanus , and C. saltator , with more anteriorly placed anterior suture of the frontoparietal and prootic than in other species. Specimens were dissected; three (UTA A-62392, 66098, and MZFC-HE-35582) seem to be subadult females with unpigmented ovaries and thin undeveloped oviducts, UTA A-66097 is an adult female with a thickened oviduct and also unpigmented ovaries containing yolked eggs, UTA A-66098 adult and MZFC-HE-35582 subadult are males with pigmented testes (smaller on second specimen), and the hatchling (8.2 mm SVL) was not dissected. This species likely co-occurs with C. candelariensis , C. portilloensis , and C. pygmaeus in southcentral Oaxaca ( Figs. 6 and 8 ). It was collected in sympatry with C. portilloensis at Portillo del Rayo, Oaxaca, Mexico ( Fig. 8 ). The hatchling paratype specimen (UTA A-55246) had no evidence of skeletal ossification ( Fig. 11 ).

Figures

FIG. 31.—Subadult female holotype of Craugastor polaclavus (UTA A- 62392, SVL ¼ 14.7 mm) from San Pedro Pochutla district, Portillo del Rayo, Oaxaca, Mexico, 1550–1585 m. A color version of this figure is available online.

FIG. 25.—View from the type locality of Craugastor hobartsmithi, Uruapan, Michoacán, looking toward Cerro Tancitaro (A). Craugastor cf. hobartsmithi; female (B, UTA A-66134, SVL ¼ 13.2 mm); male (C, MZFC-HE-35613, SVL ¼ 9.6 mm); female (D, UTA A-66133, SVL ¼ 18.3 mm); all from near Las Playitas (Carretera Playitas–Torre de Microndas), Michoacán, Mexico, 1565 m. Craugastor cf. hobartsmithi from Montitlan, Colima, Mexico photographed 13 April 2020 (E, F, not collected, photo by J. Reyes-Velasco). A color version of this figure is available online.

FIG. 7.—Box plots depicting elevational distribution of Craugastor mexicanus and C. pygmaeus inferred from locality data associated with museum specimens. Results are shown for both specimens used in the molecular analysis (Molecules þ Morphology) and for specimens assigned to species using only morphology. Asterisks represent potential outliers, which are.1.5 times the interquartile range (¼ range inside the box).

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.

FIG. 5.—Maximum Likelihood analysis of nuclear DNA (nDNA) markers sequenced from the Craugastor mexicanus series (total of 1183 base pairs). Black circles indicate nodes receiving bootstrap support values.90 from the Maximum Likelihood analysis and 0.90 posterior probabilities in corresponding Bayesian analyses. Where posterior probabilities were.0.90 but Maximum Likelihood bootstrap support was,90, a number indicates the bootstrap support. NS indicates no support in the Bayesian analysis for a depicted relationship. Locality abbreviations are as follows: COL ¼ Colima, GRO ¼ Guerrero, JAL ¼ Jalisco, MEX ¼ Estado de México, OAX ¼ Oaxaca, PUE ¼ Puebla, and VER ¼ Veracruz.

FIG. 4.—Maximum Likelihood analyses of mitochondrial DNA (mtDNA) markers sequenced from the Craugastor mexicanus series (total of 1047 base pairs). Black circles indicate nodes receiving bootstrap support values.90 from the Maximum Likelihood analysis and 0.90 posterior probabilities in corresponding Bayesian analyses. Where posterior probabilities were.0.90 but Maximum Likelihood bootstrap support was,90, a number indicates the bootstrap support. 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.

FIG. 6.—Distribution of Craugastor mexicanus, C. montanus, C. pygmaeus, and C. saltator in Mexico and Guatemala. Dots inside symbols indicate individuals used in the molecular analyses in this study. Relevant type localities are indicated by text and arrows.

FIG. 8.—Distribution of Craugastor hobartsmithi, C. cf. hobartsmithi, C. omiltemanus and six new species from Mexico. Dots inside symbols indicate individuals used in the molecular analyses in this study. Inset depicts region of Oaxaca where three of the new species exist in near sympatry. A question mark indicates uncertain georeferencing. Relevant type localities are indicated by text and arrows.

FIG. 11.—Ossification levels within the Craugastor mexicanus series compared with body size (estimated as log centroid size). Ossification scores are based on the six-stage ontogenetic sequence described in Table 3.