Craugastor pygmaeus ( Taylor 1936 )

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 : 34-35

Craugastor pygmaeus ( Taylor 1936)

Eleutherodactylus pygmaeus Taylor 1936:352 . Holotype female ( UIMNH 16125 ) from ‘‘one mile north of Rodriguez Clara, Veracrux, Mexico.’’ [Examined] .

Microbatrachylus albolabris Taylor 1940:502 . Holotype female ( FMNH 100071 ) from ‘‘two miles west of Córdoba, Veracruz, Mexico.’’ [Examined] .

Microbatrachylus pygmaeus (Taylor) : Taylor 1940:500.

Microbatrachylus minimus Taylor 1940:507 . Holotype male ( FMNH 100323 ) from ‘‘Agua del Obispo, Guerrero, Mexico.’’ [Examined] .

Microbatrachylus imitator Taylor 1942:70 . Holotype female ( USNM 115508 ) from ‘‘La Esperanza, Chiapas, Mexico.’’ [Examined] .

Craugastor pygmaeus (Taylor) : Crawford and Smith 2005:536.

Diagnosis. —Based on 37 specimens. Aspecies of Craugastor distinguished by the following combination of characters: (1) small adult size (mean SVL ¼ 13.5 mm [SD ¼ 1.77], n ¼ 29); (2) full ossification of skeletal elements in adults; (3) lack of posterolateral projection of frontoparietal; (4) lack of vomerine odontophores; (5) presence or absence of raised tubercles on eyelids; (6) supratympanic fold absent or poorly developed; (7) face flank barred canthus and jaws (rarely dark and blotched), no canthal stripe; (8) one (or two fused) postrictal tubercles; (9) gular region pigmentation present or absent; (10) dorsal surface two-toned usually with dark suprascapular ^^shape, or striped and with pale middorsal stripe; (11) variable middorsal ridge; (12) dorsum smooth or with only some large scattered tubercles; (13) body flank barred darker anteriorly, slightly shagreened to smooth; (14) inguinal glands present and axillary glands absent in adults; (15) when leg adpressed to body, heel reaches between eye and slightly beyond tip of snout; (16) outer tarsal ridge smooth, no raised fringe; (17) finger and toe pads round, expanded; (18) inner metatarsal tubercle larger than outer metatarsal tubercle.

Comparisons. — Craugastor pygmaeus 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. pygmaeus ). It can be differentiated from C. mexicanus , C. montanus , C. omiltemanus , C. polaclavus , C. rubinus , and C. saltator by the presence of a posterolateral projection of the frontoparietal (absent in C. pygmaeus ; Fig. 26C ). Craugastor pygmaeus is most similar to C. bitonium (in morphology, osteology, and genetic distance), but may be differentiated from this taxon by the condition of the outer tarsal ridge, which is smooth in C. pygmaeus versus 1–6 small tubercles in C. bitonium .

Description. —In previous literature, described as smallbodied (‘‘diminutive’’) and short-limbed, with unequal inner and outer metatarsal tubercle sizes; distinct subarticular tubercles; barely visible supernumerary tubercles; no vomerine odontophores ( Taylor 1936); rounded canthus; two palmar tubercles ( Taylor 1942).

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Holotype ( UIMNH 16125) ~ 18 mm SVL. Among select specimens that we examined, we observed short, rounded snout (naris–snout ¼ 0.78 mm, SD ¼ 0.14, n ¼ 29; 5.8% SVL); long eye–nostril distance (1.19 mm, SD ¼ 0.24, n ¼ 29; 8.9% SVL); some specimens with single palmar tubercle; relative finger lengths III> IV> II ¼ I; relative toe lengths IV <III < V <II < I; color pattern in life variable ( Fig. 33 ).

Distribution. —Widely distributed throughout lowland to intermediate localities in the states of Chiapas, Puebla, Oaxaca, and Veracruz (also possibly Tabasco, Mexico, and western Guatemala) from near sea level to 2000 m ( Fig. 6 ). Canseco Márquez and Gutiérrez Mayén (2010) report C. pygmaeus occurs in the forests adjacent to the Tehuacán– Cuicatlán Valley in Puebla and Oaxaca. The western range edge of C. pygmaeus is uncertain; we examined one specimen (UTA A-66131) a male with pigmented testes, from San Vicente de Benitez (17.290618N, 100.279558W, 951 m), Guerrero, collected 17 June 2004, that appears referable to C. pygmaeus .

Diet. —One male specimen (UTA A-64263, determined by the presence of pigmented testes), was found to contain ants ( Formicidae ) in its stomach.

Phylogenetics. — Craugastor pygmaeus was inferred to be the sister taxon of C. bitonium with high support in the concatenated analyses (ML ¼ 99; BAYES ¼ 1.0; Fig. 3 ). This sister relationship was also recovered in both mtDNA and nDNA analyses, although with lower support in the nDNAonly analyses (ML ¼ 54, BAYES ¼ 0.67; Figs. 4 and 5 ). Craugastor pygmaeus is separated from C. bitonium by a P - distance of 4.7% ( Table 4 ).

Remarks. —The skull of C. pygmaeus is similar to C. hobartsmithi and C. montanus , with more posteriorly placed anterior suture of the frontoparietal and prootic than in other species. Despite how common this species is in most museum collections, we know very little about its natural history, including reproductive behavior, call, and diet. This species likely co-occurs with C. candelariensis , C. polaclavus and C. portilloensis in southcentral Oaxaca and (possibly) C. bitonium in central Guerrero. It may overlap with (1) C. montanus in Chiapas, (2) C. mexicanus at intermediate elevations of the Sierra Madre del Sur and Sierra Madre Oriental ( Fig. 7 ), and (3) C. hobartsmithi in central and western Guerrero. Males likely have larger tympana than do females ( Figs. 13 and 33 ).

Figures

FIG. 26.—Skulls of ‘Microbatrachylus lineatissimus’ (A, paratype, FMNH 104548), Craugastor mexicanus (B, UTA A-56558) and C. pygmaeus (C, UTA A- 64272) in dorsal and lateral views. Posterolateral projection of the frontoparietal on C. mexicanus (B) is indicated by an arrow and grey shading. A color version of this figure is available online.

FIG. 33.—Male Craugastor pygmaeus (A, UTA A-64283, SVL ¼ 14.6 mm, photo by Matthew Ingrasci) from Oaxaca, Mexico; female (B, UTA A-64262, SVL ¼ 13.7 mm) from Oaxaca, Mexico; female (C, UTA A-64266, SVL ¼ 17.0 mm) from Oaxaca, Mexico; male (D, UTA A-64263, SVL ¼ 12.4) from Guerrero, Mexico. A color version of this figure is available online.

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. 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. 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. 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. 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. 13.—Evidence of sexual dimorphism of tympanum width in Craugastor mexicanus (left) and C. pygmaeus (right). Sex was determined by directly examining gonads for select specimens of C. mexicanus and is implied by scaling patterns in those specimens where sex was not directly determined. Downloaded From: https://bioone.org/journals/Herpetological-Monographs on 04 May 2022