  University of Kansas Publications, Museum of Natural History Editors of this number: Frank B. Cross, Philip S. Humphrey, William E. Duellman Volume 20, No. 1, pp. 1-45, 22 figs. Published February 20, 1970 University of Kansas Lawrence, Kansas PRINTED BY THE UNIVERSITY OF KANSAS PRINTING SERVICE LAWRENCE, KANSAS 1970 A Taxonomic Revision of the Leptodactylid Frog Genus Syrrhophus Cope BY JOHN D. LYNCH Introduction Cope (1878) proposed the genus Syrrhophus for a medium-sized leptodactylid frog from central Texas; in the ensuing 75 years the genus was expanded to include a heterogeneous group of frogs ranging from Texas to Peru. Taylor (1952) and Firschein (1954) limited the genus to several species of frogs occurring in Guatemala, MÉxico, and Texas. Lynch (1968) provided a definition of the previously loosely-defined genus. With the exception of Taylor (1952), who treated the Costa Rican species, none of these authors dealt with the present status of the nineteen species erroneously assigned to Syrrhophus. These species are listed in Tables 1 and 2 with the name currently applied. Some of them are new combinations and their justifications will be published elsewhere. Gorham (1966) is the most recent author to include South American species in the genus Syrrhophus. Smith and Taylor (1948) recognized two species groups of the genus in MÉxico, an eastern and a western group (here termed complexes for purposes of discussion), separated on the basis of the number of palmar (metacarpal) tubercles (three palmar tubercles in the members of the eastern complex and two in those of the western complex). Duellman (1958) reviewed the species of the genus occurring in western MÉxico and concluded that there were five species (two polytypic). Dixon and Webb (1966) described an additional species from Jalisco, MÉxico. The distributions of some species have been extended, but otherwise the western complex of species remains unchanged since Duellman's review. Smith and Taylor (1948) recognized seven species of the genus in eastern MÉxico. Firschein revised the eastern complex (as then understood), and in so doing added one new species and treated Syrrhophus verruculatus as a nomen dubium. Dixon (1957) redefined the related genus Tomodactylus and transferred T. macrotympanum Taylor to the genus Syrrhophus. Neill (1965) described a new subspecies of S. leprus from British Honduras. Two species (S. gaigeae and S. marnockii) were recognized in Texas until Milstead, Mecham, and McClintock (1950) synonymized S. gaigeae with S. marnockii. Thus, at present, nine species (one polytypic) are recognized on the eastern slopes and lowlands from central Texas to British Honduras. These are currently placed on one species group equivalent to the western complex reviewed by Duellman (1958). Table 1—Species Described as Members of the Genus Syrrhophus but Now Placed in Other Genera.
[1] New combination. Table 2—Species Incorrectly Regarded as Members of the Genus Syrrhophus but Described as Members of Other Genera.
Table 3—Nominal Species of Syrrhophus (sensu strictu) and the Name Used Herein.
In the course of preparing an account of the species of Eleutherodactylus occurring in MÉxico and northern Central America, it became necessary to reËxamine the status of the genus Syrrhophus and its nominal species. It soon became evident that there were more names than species, that some previously regarded species were geographic variants, and that the eastern and western groups (complexes here) were artificial divisions of the genus. I conclude that there are seven species (one polytypic) of Syrrhophus in eastern MÉxico, Texas, and El PetÉn of Guatemala, and seven species (one polytypic) in western MÉxico. The current status of each of the 23 names correctly assigned to the genus is presented in Table 3. The fourteen species recognized by me are placed in five species groups. Two of these groups are presently placed in the western complex (modestus and pipilans groups) and three in the eastern complex (leprus, longipes and marnockii groups). The two complexes do not correspond exactly with the eastern and western groups of Smith and Taylor (1948), Firschein (1954), and Duellman (1958) since S. rubrimaculatus is now associated with the eastern leprus group. The definitions and contents of the five species groups are as follows: leprus group: digital pads not or only slightly expanded, rounded in outline; first finger longer or shorter than second; snout acuminate or subacuminate, not rounded; outer metatarsal tubercle conical; digits lacking distinct lateral fringes. content: cystignathoides, leprus and rubrimaculatus. longipes group: digital pads widely expanded, triangular in outline; first finger shorter than second; snout acuminate; outer metatarsal tubercle not conical; digits bearing lateral fringes. content: dennisi and longipes. marnockii group: digital pads expanded, rounded to truncate in outline; first finger equal in length to second or slightly shorter; snout rounded; outer metatarsal tubercle not conical; digits lacking lateral fringes; generally stout-bodied frogs. content: guttilatus, marnockii, and verrucipes. modestus group: digital pads expanded, truncate in outline; first and second fingers subequal in length, first usually slightly shorter than second; snout subacuminate; inner metatarsal tubercle twice as large (or larger) as outer metatarsal tubercle; digits bearing poorly-defined lateral fringes. content: interorbitalis, modestus, nivocolimae, pallidus, and teretistes. pipilans group: digital pads not or only slightly expanded, truncate in outline; first finger equal in length to second; snout subacuminate; metatarsal tubercles subequal in size; digits lacking lateral fringes. content: pipilans. Acknowledgments.—For loan of specimens, I am indebted to Richard J. Baldauf, Texas A & M University (TCWC); W. Frank Blair, University of Texas (TNHC); Charles M. Bogert and Richard G. Zweifel, American Museum of Natural History (AMNH); James E. BÖhlke and Edmond V. Malnate, Academy of Natural Sciences of Philadelphia (ANSP); Robert F. Inger and Hymen Marx, Field Museum of Natural History (FMNH); Ernest A. Liner (EAL); Michael Ovchynnyk, Michigan State University collection (MSU); James A. Peters, United States National Museum (USNM); Douglas A. Rossman, Louisiana State University Museum of Zoology (LSUMZ); Hobart M. Smith, University of Illinois Museum of Natural History (UIMNH); Charles F. Walker, University of Michigan Museum of Zoology (UMMZ); and John W. Wright, Los Angeles County Museum (LACM). Specimens in the collection at the University of Kansas Museum of Natural History are identified as KU. The abbreviations EHT-HMS refer to the Edward H. Taylor-Hobart M. Smith collection and FAS to the Frederick A. Shannon collection. The type-specimens from these collections are now in the Field Museum of Natural History and the University of Illinois Museum of Natural History. I have profited from discussions concerning this problem with several persons, most notably William E. Duellman, Hobart M. Smith, Edward H. Taylor and Charles F. Walker. Nevertheless, the ideas and conclusions presented here should not be construed as necessarily reflecting their opinions. David M. Dennis executed all of the figures, and my wife, Marsha, typed the manuscript. Materials and Methods.—In the course of this study, 1003 specimens of the genus were examined. The holotypes of 21 of the 23 nominal species are extant; I have examined 19 of these. Nine measurements were taken, and five ratios computed for each of 338 specimens. Females are available for all species but one; thus, measurements were taken on individuals of both sexes. Analysis of Characters Size and proportions.—Frogs of this genus range in size from 16 to 40 mm. in snout-vent length. Five species are relatively small: S. cystignathoides, modestus, nivocolimae, pallidus and rubrimaculatus; one, S. longipes, is relatively large, and the remaining eight species are intermediate in size (22-30 mm.). Males are generally smaller than females and have proportionately longer heads and usually larger tympani. No significant differences were found among proportions, except that S. longipes has a larger tympanum/eye ratio than any other species. Frogs in the Syrrhophus marnockii group tend to have shorter shanks and feet, thereby giving those species a more stocky appearance. However, the differences are not significant. A summary of the data on size and proportions for the frogs of the genus Syrrhophus is given in Tables 4, 5, and 6. Hands and Feet.—Taylor and Smith (1945), Smith and Taylor (1948), Firschein (1954) and Duellman (1958) discussed the value of the palmar tubercles in identifying frogs of this genus. The eastern complex in general has a well-developed outer palmar tubercle (Fig. 1) in distinction to the western complex in which the outer palmar tubercle is reduced or absent (Fig. 2). Dixon and Webb (1966) imply that the outer palmar tubercle is rarely absent but is usually smaller than the first supernumerary tubercle of the fourth finger. My study of the western species demonstrates that the outer palmar tubercle is indeed usually present and smaller than the first supernumerary tubercle. Differences in interpretation of the terms "unexpanded" and "narrow," as well as differences in techniques of preservation, have led to confusion of the reported digital shapes in various species. Constant specific differences are evident in the hands (Fig. 1). Except in the cases of excessive uptake of fluids, all species have a terminal transverse groove at the tip of each digit. Taylor (1940b) stated that S. smithi lacked grooves, but examination of the holotype reveals faint grooves at the tops of the digits. Syrrhophus guttilatus, leprus, pipilans, and verrucipes lack lateral fringes on the fingers. Lateral fringes are well developed in the longipes and modestus groups but poorly defined or absent in the other members of the genus. The digital pads of the frogs of the longipes group are much broader than those of the other species and are narrowest in the frogs of the leprus group. Supernumerary tubercles are present on the palmar surfaces of all species of the genus. Table 4—Size and Proportions in the Frogs of the Syrrhophus leprus Group.
Table 5—Size and Proportions in the Frogs of the Syrrhophus longipes and S. marnockii Groups.
Table 6—Size and Proportions in the Frogs of the Syrrhophus pipilans and S. modestus Groups.
Fig. 1: Palmar views of hands of six species of the eastern complex of Syrrhophus. (A) verrucipes (UIMNH 15995), (B) rubrimaculatus (KU 58911), (C) dennisi sp. nov. (holotype, UMMZ 101121), (D) guttilatus (UIMNH 55520), (E) marnockii (TCWC 4782), and (F) longipes (TCWC 12179). All ×6.5. Fig. 2: Palmar views of hands of two species of the western complex of Syrrhophus. pipilans (left, KU 58908, ×6) and teretistes (center, KU 75269, and right, KU 75263, respectively, ×9). In S. cystignathoides and leprus, the first finger is longer than the second, and the first two fingers are equal in length in guttilatus and marnockii. In the other species the first finger is shorter than the second. Supernumerary tubercles are well developed on the plantar surfaces in all species, except S. guttilatus, in which they are poorly defined (Fig. 3). The relative sizes of the metatarsal tubercles has been used in the classification of the species and species groups of Syrrhophus. The metatarsal tubercles are similar in all species of the eastern complex (including rubrimaculatus); the outer tubercle is always about one-half the size of the ovoid inner metatarsal tubercle. In the leprus group the outer tubercle is conical and compressed. The metatarsal tubercles of pipilans are about the same size, or the outer is slightly smaller than the inner. In the modestus group the outer metatarsal tubercle is about one-third the size of the inner. All species, except guttilatus, have well-defined to poorly defined lateral fringes on the toes. All species have expanded toe pads. The fifth toe is usually shorter than the third, but the second is equal in length to the fifth in some specimens of S. cystignathoides and S. marnockii. Syrrhophus nivocolimae is the only species with tubercles along the outer edge of the tarsus; this is merely a reflection of the highly tuberculate nature of the skin in this species. Skin texture.—The skin of the dorsum is smooth or very weakly pustular in all species of the genus except nivocolimae and verrucipes. The dorsal surfaces of nivocolimae are warty; in verrucipes the skin is pustular. The skin of the venter is areolate in cystignathoides cystignathoides, dennisi and verrucipes but is smooth in all other species of the genus. Fig. 3: Plantar views of feet of four species of the eastern complex of Syrrhophus. (A) guttilatus (UIMNH 55519, ×6), (B) leprus (UIMNH 42726, ×6), (C) verrucipes (UIMNH 15995, ×6), and (D) longipes (TCWC 12179, ×4.6). Color pattern.—As is evident in the diagnoses, the color patterns of given populations have been regarded as useful in separating the species and subspecies. Duellman (1958) suggested that the coloration, with the exception of modestus, was a dark ground color with pale markings. It is a moot point whether the frogs have light spots on a dark background or have a light background with an extensive reticulate dark pattern. The venters are gray or white, and the vocal sac is nearly black in some species. Interorbital dark bars or triangles are absent in only two species of the eastern complex, cystignathoides campi and marnockii; the latter lacks a supratympanic stripe, which is present in the other members of the eastern complex. Syrrhophus interorbitalis and nivocolimae have light interorbital bars; these bars occur in only one other population of the genus (S. c. cystignathoides). Bars on the thighs are ill defined or absent in the members of the marnockii and part of the modestus groups. The color in life is noted in the species accounts. Voice.—The voices of all Syrrhophus can be described as a single short chirp or peep; without audiospectrographic analyses the significance of the differences between a chirp, peep, or short whistle cannot be appreciated. Martin (1958) and Wright and Wright (1949) reported multi-noted calls, and one collector of S. verrucipes noted the frog "trilled." Fouquette (1960) presented analyses of two species (marnockii and pipilans nebulosus). The voices were very similar; both frogs were reported to "trill" and "chirp." Systematic Account The genus Syrrhophus has been defined (Lynch, 1968) and limited to the group of species occurring in Guatemala, MÉxico and the United States. The closest relatives of Syrrhophus are the frogs of the genus Tomodactylus (Dixon, 1957; Firschein, 1954). Lynch (1968) implied there were no osteological bases for the separation of Eleutherodactylus, Syrrhophus, and Tomodactylus. At that time, I believed such to be the case and derived Syrrhophus and Tomodactylus from the rhodopis complex of Eleutherodactylus, with which they share terrestrial habits and relatively short limbs. In the rhodopis complex there is a tendency for the loss of the outer palmar tubercle, a not uncommon condition in Syrrhophus and Tomodactylus. However, the skulls of Syrrhophus and Tomodactylus show departures from the pattern observed in the Middle American Eleutherodactylus, as well as many of those species in western South America. Baldauf and Tanzer (1965) reported that the frontoparietals and prootics were fused in Syrrhophus marnockii and that the prootics and exoccipitals appeared to be one bone (otoccipital). The otoccipital is not uncommon in eleutherodactyline frogs, but the fusion of the frontoparietals with the prootics (regardless of the fusion of the latter with the exoccipital) is uncommon in the family. I have found the frontoparietal-prootic fusion only in Syrrhophus (all species), Tomodactylus (all species), and Eleutherodactylus (West Indies species). None of the Middle American Eleutherodactylus has the two bones fused. Examination of the character is difficult in dried skeletal preparations. Cleared and stained or macerated preparations are satisfactory for checking this character. Thus, in addition to the presence of numerous plantar supernumerary tubercles in the frogs of the genera Syrrhophus and Tomodactylus, these two genera can be separated from other Middle American eleutherodactylines by the fusion of the frontoparietals and prootics. This character not only further strengthens the argument that the two genera are closely related but poses a problem of zoogeographic analysis of the distribution of the character, which will be discussed fully elsewhere. Key to the Species of the Frog Genus Syrrhophus Species Accounts The following accounts do not include complete descriptions of each taxon, because a more than adequate number of descriptions is available in the recent (1940-1966) literature. An abbreviated synonymy, in which are listed all combinations and emendations of names and significant contributions to our knowledge of the taxon, is given for each. For each species and subspecies the following are given: descriptive diagnosis, statement of range, remarks on taxonomy, list of specimens examined, illustration of color pattern, and distribution map. Phyllobates cystignathoides Cope, 1877:89-90 [Syntypes.—Originally USNM 32402-32409, (32405 now in MCZ) from Potrero, near CÓrdoba, Veracruz, MÉxico, Francis Sumichrast collector.] Diagnosis.—Adults small, males 16.0 to 23.5 mm. in snout-vent length, females 16.0-25.8 mm. in snout-vent length; vocal slits present in males; finger tips slightly expanded; first finger longer than second; outer metatarsal tubercle one-half size of inner, conical, compressed; skin of dorsum weakly pustular, that of venter smooth to areolate; tympanum 44 to 69 per cent diameter of eye (mean 55.5 per cent); ground color yellow to brown in life with brown to black fleckings on dorsum and flanks; limbs banded; interorbital bar present or not. Remarks.—Two geographic races (subspecies) are herein recognized; previously these were held by various authors to be species (campi and cystignathoides). Intergradation occurs in southern Tamaulipas and eastern San Luis PotosÍ, MÉxico. The two subspecies can be distinguished on the basis of color pattern and the condition of the skin of the venter. Distribution.—Low to moderate elevations from the RÍo Grande embayment to central Veracruz, MÉxico (Fig. 5). |
|