Pectoral Girdle
All species have large cartilaginous plates in the pectoral girdles; none possesses a bony style. No divergent modifications of the clavicle and coracoid bones are known in the family.
GENERIC ACCOUNTS
Genus Eleutherodactylus Dumeril and Bibron, 1841
Type-species.—Hylodes martinicensis Tschudi, 1838
Diagnosis and definition.—Small to large frogs (12 to 110 mm. snout-vent length) having slightly to widely expanded digital pads, each pad bearing a terminal transverse groove; lumbo-inguinal, inguinal, and axillary glands absent, or if present, diffuse, irregular in outline, not compact; plantar supernumerary tubercles absent, or if present, six or fewer, restricted to distal area of plantar surface, and not extending between metatarsal tubercles; tarsus bearing inner or outer tubercles or folds or not; toes free to one-half webbed; terminal phalanges T-shaped; sternum cartilaginous, lacking bony style; sphenethmoid not truncate anteriorly; nasals in contact medially; maxillary and quadratojugal in contact; anterior arm of squamosal not in contact with maxillary; dermal cranial elements not involved in integumentary-cranial co-ossification; prevomers large, dentigerous processes present or not, dentate or not; maxillary and premaxillary bones dentate; occipital condyles separated; development direct.
Composition.—About 420 names have been applied to frogs of this genus; many of these names are synonyms, and many other species remain undescribed and unnamed. Perhaps the genus contains 350 species. Thirty-one species occur in México and northern Central America.
Distribution.—From Tamaulipas and Sinaloa, México, exclusive of the Mexican Plateau, to at least Peru and southernmost Brazil and throughout the West Indies. Introduced into Florida.
Etymology.—Greek (eleuthero + dactylus) meaning free-toed.
Genus Engystomops Jiménez de la Espada, 1872
Type species.—Engystomops petersi Jiménez de la Espada, 1872
Diagnosis and definition.—Small frogs (20 to 40 mm. snout-vent length) having undilated digital tips lacking transverse grooves; lumbo-inguinal or inguinal glands absent; plantar supernumerary tubercles present, extending between metatarsal tubercles; tarsus bearing spinelike tubercle on inner edge; toes free; terminal phalanges pointed; sternum bearing bony style; spenethmoid not truncate anteriorly; nasals in contact medially; maxillary and quadratojugal in articular contact; anterior arm of squamosal not in contact with maxillary; dermal cranial elements not involved in integumentary-cranial co-ossification; prevomers moderate in size, lacking teeth; maxillary and premaxillary bones edentate; occipital condyles separated; tadpole free living.
Composition.—Four nominal species (E. petersi, E. pustulatus, E. pustulosus and E. schereri).
Distribution.—Central Veracruz and eastern Oaxaca, México, to Trinidad, Bolivia, and Peru, east of the Andes.
Etymology.—Greek (engys + stoma) meaning narrow-mouthed.
Genus Hylactophryne new genus
Type-species.—Hylodes augusti Dugés, 1879
Diagnosis and definition.—Medium to large frogs (37 to 94 mm. snout-vent length) having undilated digital tips lacking terminal grooves; lumbo-inguinal or inguinal glands absent; plantar supernumerary tubercles present, prominent, extending to but not between metatarsal tubercles; tarsus lacking tubercles or folds; toes free of webbing; terminal phalanges knob-shaped, lacking elongate lateral expansions; sternum cartilaginous, lacking bony style; sphenethmoid truncate anteriorly; nasals in contact medially; maxillary and quadratojugal in articular contact; anterior arm of squamosal not in contact with maxillary; dermal cranial elements not involved in integumentary-cranial co-ossification; prevomers large, bearing dentigerous processes; maxillary and premaxillary bones dentate; occipital condyles separated; development direct.
Composition.—Two species, H. augusti and H. tarahumarensis, the former composed of four subspecies (Zweifel, 1956).
Distribution.—From Arizona, New Mexico, and Texas to Guerrero and Puebla, México, and a relict population on Cerro Quingola (just west of the Isthmus of Tehuantepec, México).
Etymology.—Greek (hylactor + phryne) meaning barking toad; in reference to the voice and common name.
Genus Leptodactylus Fitzinger, 1826
Type-species.—Leptodactylus typhonia Fitzinger, 1826
Diagnosis and definition.—Small to large frogs (30 to about 200 m., snout-vent length) having undilated to slightly expanded digital tips bearing pads, no transverse groove at tips of digits; lumbo-inguinal, axillary, and/or ventral glands present or not, low, diffuse; plantar supernumerary tubercles generally absent, if present not extending between metatarsal tubercles; tarsus bearing tarsal folds or not; toes free of webbing, extensive lateral fringes present in some species; terminal phalanges pointed, not T-shaped; sternum bearing bony style; sphenethmoid not truncate anteriorly; nasals in contact medially; maxillary and quadratojugal in articular contact; anterior arm of squamosal not in contact with maxillary; dermal cranial elements not involved in integumentary-cranial co-ossification; prevomers large, bearing dentigerous processes; maxillary and premaxillary bones dentate; occipital condyles separated; tadpole free living.
Composition.—Sixty species according to Smith and Taylor (1948); 54 according to Gorham (1963); Argentinian authors have described several more in recent years.
Distribution.—Southern Sonora, México, and southern Texas throughout the Central and South American lowlands to Argentina. Also known from Hispaniola and Puerto Rico in the Greater Antilles and a few islands in the Lesser Antilles.
Entymology.—Greek (leptos + dactylus) meaning slender toes.
Genus Syrrhophus Cope, 1878
Type-species.—Syrrhophus marnockii Cope, 1878
Diagnosis and definition.—Small to medium sized frogs (18 to 40 mm. snout-vent) having slight to prominent digital expansions with transverse groove at tip of each digit; lumbo-inguinal and inguinal gland flattened, irregular in outline, not compact and oval; axillary glands present or not; plantar supernumerary tubercles numerous, more than eight, usually extending between metatarsal tubercles; tarsus lacking tubercles or folds; toes free or basally webbed; terminal phalanges T-shaped; sternum cartilaginous, lacking bony style; sphenethmoid not truncate anteriorly; nasals in contact medially; maxillary and quadratojugal in articular contact; anterior arm of squamosal not in contact with maxillary; dermal cranial elements not involved in integumentary-cranial co-ossification; prevomers large, usually lacking dentigerous processes and teeth; maxillary and premaxillary bones dentate; occipital condyles separated; development direct.
Composition.—Thirteen species; the species described as, or later referred to, Syrrhophus from Lower Central America and South America are Eleutherodactylus or Eupsophus.
Distribution.—Low to moderate elevations from Sinaloa, México, to Guatemala on the Pacific versant; from the Edwards and Stockton plateaus of Texas to British Honduras on the Caribbean versant.
Etymology.—Greek, emendation of syrrhaptos, meaning sewn together in reference to the united outer metatarsals.
Genus Tomodactylus Günther, 1900
Type-species.—Tomodactylus amulae Günther, 1900.
Diagnosis and definition.—Small frogs (20 to 35 mm. snout-vent length) having digital expansions or not, with transverse groove across tip of each digit; lumbo-inguinal gland prominently elevated, compact, oval, often patterned; axillary glands absent; plantar supernumerary tubercles numerous, more than eight, usually extending between metatarsal tubercles; tarsus lacking tubercles or folds; toes free; terminal phalanges T-shaped; sternum cartilaginous, lacking bony style; sphenethmoid not truncate anteriorly; nasals in contact medially; maxillary and quadratojugal in articular contact; anterior arm of squamosal not in contact with maxillary; dermal cranial elements not involved in integumentary-cranial co-ossification; prevomers large, usually bearing dentigerous processes; maxillary and premaxillary bones dentate; occipital condyles separated; development direct.
Composition.—Ten species.
Distribution.—The southern edge of the Mexican Plateau from Sinaloa to Veracruuz and onto the Oaxaca highlands and Sierra Madre del Sur.
Etymology.—Greek (tomis + dactylus) meaning knife toe; in reference to either the sharp subarticular tubercles or the unwebbed toes.
DISCUSSION
The preceding definitions only slightly alter the present generic limits of Mexican leptodactylids. Two species, previously regarded as Eleutherodactylus, are transferred to the new genus Hylactophryne. The arrangement of the species of Syrrhophus and Tomodactylus remains the same as concluded by Dixon (1957), Duellman (1958), and Firschein (1954) in their reviews of the genera.
Lumbo-inguinal glands are most prominent in the genera Pleurodema and Tomodactylus. Various nondescript glands are present in many genera, but none is so well developed as those of Pleurodema and Tomodactylus.
At least nine leptodactylid genera are either known or thought to be terrestrial breeders lacking a free-living tadpole stage (Eleutherodactylus, Euparkerella, Hylactophryne, Niceforonia, Noblella, Sminthillus, Syrrhophus, Tomodactylus and Trachyphrynus). Niceforonia and Trachyphrynus, and probably Hylactophryne, are not closely related to the other genera. Direct development probably is an adaptation to adverse environmental conditions since many of the species occur in semi-arid or cold (Andean páramos) areas. Eleutherodactylus is generally thought to be the stock from which Euparkerella, Noblella, and Sminthillus evolved (Griffiths, 1959) and from which Syrrhophus and Tomodactylus are derived (Firschein, 1954).
The present distribution of Hylactophryne (isolated on the Mexican Plateau) and its digital form (like that of Papuan and many primitive South American leptodactylids) suggest that the genus was isolated in México throughout the Tertiary, whereas the other Central American genera are either post-Pliocene derivatives of Eleutherodactylus or invaders of Central America from South America since the mid-Pliocene land bridge was formed (Lloyd, 1963).
Piatt (1934) presented arguments against assigning Eleutherodactylus latrans to the genus Lithodytes and concluded that it was a "true" Eleutherodactylus. Contrary to his arguments, latrans (= augusti of Zweifel) and E. tarahumarensis Taylor differ from all other Eleutherodactylus (and Syrrhophus and Tomodactylus) in the nature of the tips of the digits (external and skeletal). The digits of Hylactophryne are like those of Eupsophus. My study of nearly all genera of leptodactylids indicates that Noble (1925) was correct in suggesting that Borborocoetes (= Eupsophus) is a close relative of Eleutherodactylus latrans, although Noble's arguments were based in part upon false evidence concerning the breeding habits of E. latrans, then thought to have a free-living tadpole.
Kellogg (1932) and Piatt (1934) argued that the terminal phalanges of E. latrans were typically eleutherodactyline. The variation of this character in Eupsophus (see [Fig. 4]) ranges from knobbed to bifurcate or Y-shaped (T-shaped in Eleutherodactylus, Syrrhophus and Tomodactylus) and encompasses the nature of the character represented in Hylactophryne. Eupsophus differs from Hylactophryne in possessing a frontoparietal fontanelle, in generally having a maxillary-quadratojugal gap, and in having a free swimming tadpole stage.
Fig. 5. Outline drawings of Leptodactylus melanonotus (left, KU 65704, × 2) and Eleutherodactylus alfredi (right, KU 93994, × 2).
KEY TO MEXICAN LEPTODACTYLID GENERA
| 1. | Small (20-40 mm.), pustular, toadlike frogs; maxillary and premaxillary bones not bearing teeth | Engystomops |
| Large (20-110 mm.), smooth skinned and non-toadlike frogs; maxillary and premaxillary bones bearing teeth | 2 | |
| 2. | No conspicuous waist ([Fig. 5]); sternum bearing bony style, | Leptodactylus |
| Constrictions at waist ([Fig. 5]); sternum cartilaginous, no bony style | 3 | |
| 3. | Few (less than six), if any, supernumerary tubercles on plantar surface | Eleutherodactylus |
| Many (more than 8) supernumerary tubercles on plantar surfaces | 4 | |
| 4. | Terminal, transverse groove across tip of digits, especially outer two fingers, digits expanded or not; small frogs (18 to 40 mm.) | 5 |
| Tips of digits lacking transverse groove; digits unexpanded; medium-sized to large frogs (37 to 94 mm.) | Hylactophryne | |
| 5. | Lumbo-inguinal gland compact, oval | Tomodactylus |
| Lumbo-inguinal or inguinal gland absent or diffuse and irregular in outline | Syrrhophus |
LITERATURE CITED
Dixon, J. R.
1957. Geographic variation and distribution of the genus Tomodactylus in Mexico. Texas Jour. Sci., 9:379-409, December.
Duellman, W. E.
1958. A review of the frogs of the genus Syrrhophus in western Mexico. Occas. Papers Mus. Zool. Univ. Michigan, 594:1-15, June 6.
1961. The amphibians and reptiles of Michoacan, Mexico. Univ. Kansas Publ. Mus. Nat. Hist., 15:1-148, December 20.
Firschein, I. L.
1954. Definition of some little understood members of the leptodactylid genus Syrrhophus, with a description of a new species. Copeia, 1:48-58, February 19.
Gallardo, J. M.
1965. A proposito de los Leptodactylidae (Amphibia Anura). Papeis Avulsos, 17:77-87, January 30.
Gorham, S. W.
1963. The comparative number of species of amphibians in Canada and other countries. III. Summary of species of anurans. Canadian Field-Nat., 77:13-48, March.
Griffiths, I.
1959. The phylogeny of Sminthillus limbatus and the status of the Brachycephalidae (Amphibia Salientia). Proc. Zool. Soc. London, 132:457-87, May.
Kellogg, R.
1932. Mexican tailless amphibians in the United States National Museum. Bull. U. S. Natl. Mus., 160:224 pp., March 31.
Lloyd, J. J.
1963. Tectonic history of the south Central-American orogen, in Childs and Beebe eds., Backbone of the Americas. Amer. Assoc. Petroleum Geol., pp. 88-100.
Lynch, J. D.
1965. A review of the eleutherodactylid frog genus Microbatrachylus (Leptodactylidae). Nat. Hist. Misc., 182:1-12, December 15.
Myers, G. S.
1962. The American leptodactylid frog genus Eleutherodactylus, Hylodes (= Elosia), and Caudiverbera (= Calytocephalus). Copeia, 1:195-202, April 11.
Noble, G. K.
1925. An outline of the relation of the ontogeny to phylogeny within the Amphibia. I. Amer. Mus. Nov., 165:1-17, April 16.
Piatt, J.
1934. The systematic status of Eleutherodactylus latrans (Cope). Amer. Midl. Nat., 15:89-91, February 15.
Smith, H. M. and Taylor, E. H.
1948. An annotated checklist and key to the Amphibia of Mexico. Bull. U. S. Natl. Mus., 194:1-118. June 7.
Taylor, E. H.
1952. A review of the frogs and toads of Costa Rica. Univ. Kansas Sci. Bull., 35:577-942, July 1.
Zweifel, R. G.
1956. A survey of the frogs of the augusti group, genus Eleutherodactylus. Amer. Mus. Novitates, 1813:1-35, December 23.
Transmitted July 11, 1967.
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