UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY Volume 17, No. 11, pp. 503-515, 5 figs. March 20, 1968 Genera of Leptodactylid Frogs in México BY JOHN D. LYNCH UNIVERSITY OF KANSAS LAWRENCE 1968 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Frank B. Cross Volume 17, No. 11, pp. 503-515, 5 figs. Published March 20, 1968 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY ROBERT R. (BOB) SANDERS, STATE PRINTER TOPEKA, KANSAS 1968 31-9418 Genera of Leptodactylid Frogs in México BY JOHN D. LYNCH INTRODUCTION According to the most recent review of the Mexican amphibian fauna (Smith and Taylor, 1948), six genera of leptodactylid frogs occur in México. One other genus, _Pleurodema_, occurs in Lower Central America. Smith and Taylor recognized one species of _Engystomops_, 28 of _Eleutherodactylus_, three of _Leptodactylus_, eight of _Microbatrachylus_, 12 of _Syrrhophus_, and five of _Tomodactylus_. Subsequent to the publication of their checklist of the Mexican amphibia (1948), numerous taxonomic changes have been proposed. Many species of _Eleutherodactylus_ have been added to the fauna, either through the extension of their recorded ranges into México from Guatemala or by the recognition of species unknown in 1948, whereas some nominal species have been synonymized. _Microbatrachylus_ has been regarded as synonymous with _Eleutherodactylus_ (Lynch, 1965); four species of _Microbatrachylus_ currently are regarded as valid (Duellman, 1961, Lynch, 1965). _Syrrhophus_ was revised in part by Duellman (1958) and Firschein (1954), and a species of _Tomodactylus_ transferred to _Syrrhophus_ by Dixon (1957), who redefined _Tomodactylus_ and added more species to the genus. Since beginning my studies of the Mexican leptodactylids in 1962, I have become acutely aware of difficulties involved in defining the genera. A revision of _Eleutherodactylus_ and a review of _Syrrhophus_ are nearing completion, but prior to their publication it is desirable to redefine the genera of the Mexican leptodactylids, and in so doing recognize an heretofore unnamed genus. The definitions of _Eleutherodactylus_ and _Leptodactylus_ may need to be altered in the future, since both are widespread in South America and occur in the West Indies. Their definitions as given here are as precise as present knowledge permits. _Syrrhophus_ and _Tomodactylus_ are small assemblages that occur only in southwestern United States, México, and Guatemala. Taylor (1952) synonymized _Engystomops_ with _Eupemphix_ which, although related, should be regarded as generically distinct (Gallardo, 1965). Perhaps the most conservative classification is that of Myers (1962) who, without published evidence, combined _Eleutherodactylus_, _Syrrhophus_, and the South American _Lithodytes_ in a single genus. The major problem for students working with the Mexican leptodactylids has not been the separation of _Engystomops_ or _Leptodactylus_ from other genera but the separation and definition of the eleutherodactyline frogs currently placed in three genera, _Eleutherodactylus_, _Syrrhophus_, and _Tomodactylus_. As will be shown in this paper, these are more conveniently placed in four genera. Once a fourth genus is recognized, certain phylogenetic problems disappear and a reasonable zoogeographic interpretation is possible for Middle American leptodactylid distribution. ANALYSIS OF CHARACTERS In México and northern Central America approximately 55 species of eleutherodactyline frogs (_Eleutherodactylus_, _Syrrhophus_, and _Tomodactylus_) are known. Four genera can be recognized on the basis of the nature of inguinal glands, morphology of the hands and feet, and certain osteological features. [Illustration: FIG. 1. _Tomodactylus angustidigitorum_ (UMMZ 114305, × 4.5) illustrating the lumbo-inguinal gland typical of members of the genus. From a kodachrome by Wm. E. Duellman.] Glands Leptodactylids have a variety of glands that have been used as generic characters. Smith and Taylor (1948) regarded the so-called inguinal gland as a generic character in Mexican eleutherodaycty-lines. Lynch (1965) showed that _Eleutherodactylus_ and _Microbatrachylus_ cannot be separated by the nature of the gland or the condition of the prevomers (dentate or not). _Syrrhophus_ and _Tomodactylus_, as defined by Smith and Taylor (1948), are not generically distinct because of overlap in the condition of the prevomers and in the development of the gland. Firschein (1954) stated that _Syrrhophus_ differed from _Tomodactylus_ by having an axillary gland, but it is now known that one species of _Syrrhophus_ lacks the gland. The inguinal glands of _Eleutherodactylus_ and _Syrrhophus_, if present, are diffuse, irregular in outline, and generally not prominent; in _Tomodactylus_ the gland is higher on the body (a lumbo-inguinal gland), compact, oval in outline, and prominent (Fig. 1). Axillary glands occur in most _Syrrhophus_ but are not known in _Tomodactylus_ or _Eleutherodactylus_. Hands and feet The tips of the digits are laterally expanded in most _Eleutherodactylus_, _Syrrhophus_, and _Tomodactylus_. Two species of _Eleutherodactylus_ (_augusti_ and _tarahumarensis_) and two _Tomodactylus_ (_angustidigitorum_ and _grandis_) lack any expansion of the digital tips. All but two of the species of eleutherodactyline frogs (_E. augusti_ and _E. tarahumarensis_) have a transverse groove across the tips of the digits (Fig. 2). [Illustration: FIG. 2. Palmar views of the hands and lateral views of the tip of the third digits of _Eleutherodactylus alfredi_ (left, KU 93994, × 5) and _Hylactophryne augusti_ (right, KU 102594, × 3).] Supernumerary tubercles rarely are present on the feet of _Eleutherodactylus_, but are present and numerous in every species of _Syrrhophus_, _Tomodactylus_, and in the members of the _augusti_ group of _Eleutherodactylus_ (Fig. 3). The tubercles are small and numerous in _Syrrhophus_ and larger in _Tomodactylus_ and the _Eleutherodactylus augusti_ group. Most species of _Eleutherodactylus_ have no plantar supernumerary tubercles; a few species have such tubercles, which never extend between the metatarsal tubercles as in _Syrrhophus_ and _Tomodactylus_. [Illustration: FIG. 3. Plantar views of feet of _Eleutherodactylus alfredi_ (left, KU 93994, × 4.5), _Syrrhophus pipilans nebulosus_ (middle, KU 58900, × 7.5), and _Hylactophryne augusti_ (right, KU 102594, × 3) showing differences in size and arrangement of supernumerary tubercles.] Tarsal folds and tubercles are lacking in _Syrrhophus_, _Tomodactylus_, and the _augusti_ group of _Eleutherodactylus_. Several species of _Eleutherodactylus_ lack tarsal folds and tubercles, but in nearly every species group, one or more species possess either an inner tarsal fold, inner tarsal tubercle(s), or outer tarsal tubercles. The terminal phalanges of _Syrrhophus_, _Tomodactylus_, and all _Eleutherodactylus_ (except the frogs of the _augusti_ group) are distinctly T-shaped. In the latter, the bones are knob-shaped distally (Fig. 4). T-shaped terminal phalanges also are present in _Lithodytes_ and _Trachyphrynus_ but not in other leptodactylid genera. At least one species of _Eupsophus_ (_E. quixensis_) has terminal phalanges that resemble those of the _Eleutherodactylus augusti_ group. Several species of _Eleutherodactylus_, _Syrrhophus_, and _Tomodactylus_ with slender fingers have T-shaped terminal phalanges although the terminal dilations proportionately are only scarcely wider than the finger tips in the _Eleutherodactylus augusti_ group. The presence of a terminal groove at the tip of the finger is an external indicator of the T-shaped terminal phalanges. [Illustration: FIG. 4. Terminal phalanges of four leptodactylid frogs (all × 13.5). (a) _Eleutherodactylus mexicanus_, KU 55593; (b) _Eupsophus roseus_, KU 84731; (c) _Eupsophus quixensis_, UIMNH 59643; and (d) _Hylactophryne augusti_, KU 56192.] Skull All Mexican eleutherodactyline frogs have quadratojugal-maxillary articulations, completely roofed skulls in adults, median contact of the nasals, separated occipital condyles, and large prevomers. The premaxillae of all species are visible when the skulls are viewed from directly above. The pterygoid lacks a medioventral flange and does not meet the palatine. In no species is the anterior arm of the squamosal in contact with the maxillary. Of the numerous species examined (30 _Eleutherodactylus_, four _Syrrhophus_, and four _Tomodactylus_), the species in the _Eleutherodactylus augusti_ group are unique in having a sphenethmoid with a blunt anterior edge. 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. [Illustration: 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._ 31-9418 * * * * * Transcriber's Notes Bold text is shown within ~tildes~. Italicized text is shown within _underscores_. Illustrations have been moved to avoid breaking up paragraphs of text. Page 507: Changed know to known (are not know in Tomodactylus). Page 507: Added closing parenthesis in Fig. 2 caption after × 3. Page 509: Changed compeltely to completely (compeltely roofed skulls). Page 512: Veracruuz may be a typo for Veracruz (Sinaloa to Veracruuz). Page 514: Changed two occurrences of Hylatophryne to Hylactophryne.