Genera of Leptodactylid Frogs in México

Part 1

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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

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.

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).

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.

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.

Part 2

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.

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.

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