University of Kansas Publications
Museum of Natural History

Volume 18, No. 1, pp. 1-10
September 24, 1968

The Genera of Phyllomedusine Frogs
(Anura: Hylidae)

BY
WILLIAM E. DUELLMAN

University of Kansas
Lawrence
1968

University of Kansas Publications, Museum of Natural History

Editors of this number: Frank B. Cross,
Philip S. Humphrey, J. Knox Jones, Jr.

Volume 18, No. 1, pp. 1-10
Published September 24, 1968

University of Kansas
Lawrence, Kansas

PRINTED BY
ROBERT R. (BOB) SANDERS, STATE PRINTER
TOPEKA, KANSAS
1968

32-3687

The Genera of Phyllomedusine Frogs (Anura: Hylidae)

BY
WILLIAM E. DUELLMAN

One of the most distinctive phyletic lines among the diverse Neotropical
hylid frogs is composed of a group of 40 species placed in the genus
Phyllomedusa (Funkhouser, 1957) or in two or three different genera
(Goin, 1961; Lutz, 1966). These species differ from all other
Neotropical hylids by possessing a vertical, instead of horizontal,
pupil. The only other hylids having a vertical pupil belong to the
Papuan genus Nyctimystes. Goin (1961) erroneously stated that
Nyctimantis and Triprion have vertical pupils.

Although limited information is available on the cytotaxonomy of hylids,
the data show that phyllomedusine species have n=13 (2n=26)
chromosomes. Acris has n=11 (2n=22) (Cole, 1966). Members of
the Hyla leucophyllata, microcephala, and parviceps groups have
n=15 (2n=30), Gastrotheca ceratophrys has a haploid number of
14, the Papuan hylid genus Nyctimystes and all but one of the
Australo-Papuan Hyla for which the numbers are known have a haploid
number of 13, and all other New World hylids studied have n=12 (2n=24)
(Duellman and Cole, 1965; Duellman, 1967).

Cei (1963) and Cei and Erspamer (1966) noted that phyllomedusine frogs
differ notably from other Neotropical hylids on the basis of the amines
and polypeptides in the skin. All species of phyllomedusines deposit
their eggs in a gelatinous mass on leaves or branches above water.
Although this type of egg deposition is characteristic of some
rhacophorines and apparently all centrolenids, it is known among hylids
only in the phyllomedusines and in two species of Hyla.

The distinctive combination of morphological, physiological,
chromosomal, and behavioral characteristics is strongly suggestive that
these frogs represent an early phyletic divergence within the Hylidae.
Günther (1859) proposed the familial name Phyllomedusidae for
Phyllomedusa bicolor (Boddaert). I suggest the recognition of the
group as a subfamily. The following classification of[Pg 4] the
phyllomedusines is based on my own knowledge of the Middle American and
some South American species and on evidence from the literature on those
South American species with which I am not personally familiar.

Subfamily Phyllomedusinae Günther, 1859

Definition.—Moderately small to large hylids having vertical pupils,
n=13 (2n=26) chromosomes, skin containing large amounts of
powerful bradykinin-like and physalaemin-like polypeptides, eggs
suspended from vegetation above water, and tadpoles have a ventral
spiracle sinistral to midline.

Range.—Low and moderate elevations in South and Middle America,
including Trinidad, from northern Argentina and northwestern Ecuador to
Veracruz and southern Sonora, México.

Content.—Three genera, one of which probably is composite.

Genus Agalychnis Cope, 1864.

Definition.—Fingers and toes at least half webbed; terminal discs
large; first toe shorter than second and not opposable to others; skin
smooth, lacking osteoderms; parotoid glands, if present, poorly
developed and diffuse; palpebral membrane reticulate (except in A.
calcarifer); iris red or yellow; skull shallow, depth less than 40 per
cent of length; nasals large; frontoparietal fontanelle large;
quadratojugals reduced; prevomerine teeth present.

Range.—Central Veracruz and northern Oaxaca, México, southeastward
through Central America to northwestern Ecuador; one species disjunct in
Amazonian Ecuador.

Content.—Eight species [synonyms in brackets]: annae (Duellman,
1963); calcarifer Boulenger, 1902; callidryas (Cope, 1862)
[helenae Cope, 1885; callidryas taylori (Funkhouser, 1957)];
craspedopus (Funkhouser, 1957); litodryas (Duellman and Trueb,
1967); moreleti (Duméril, 1853) [holochroa (Salvin, 1861)];
saltator Taylor, 1955; spurrelli Boulenger, 1913.

Remarks.—Savage and Heyer (1967) provided evidence that A.
callidryas taylori (Funkhouser) and A. helenae Cope were junior
synonyms of A. callidryas (Cope).[Pg 5]

Genus Pachymedusa, new genus

Definition.—Fingers and toes having basal webs and lateral fringes;
terminal discs large; first toe shorter than second and not opposable to
others; skin smooth or shagreened, lacking osteoderms; paratoid glands
present, diffuse; palpebral membrane reticulate; iris golden yellow with
black reticulations; skull deep, depth more than 50 per cent of length;
nasals large; frontoparietal fontanelle moderately large; quadratojugal
robust; prevomerine teeth present.

Range.—Pacific slopes and lowlands from southern Sonora to the
Isthmus of Tehuantepec, México.

Content.—Monotypic: dacnicolor Cope, 1864 [alcorni Taylor, 1952].

Remarks.—The generic name is derived from the Greek pachy meaning
thick and the Greek Medousa (Latin, Medusa) in reference to
Phyllomedusa; the sense implied is the heavy body of Pachymedusa
dacnicolor.

Genus Phyllomedusa Wagler, 1830

Definition.—Fingers and toes having greatly reduced webbing or
lacking webs; terminal discs small; first toe shorter than, equal to, or
longer than second, opposable or not; skin smooth or rugose having
osteoderms or not; parotoid glands present, in most species, usually
distinct and elevated; palpebral membrane not reticulate; iris uniformly
silvery white to orange-bronze with black reticulations; skull moderate
to deep, depth more than 38 per cent of length; nasals moderately small;
frontoparietal fontanelle present, variable in size; quadratojugal
reduced in some species; prevomerine teeth present or absent.

Range.—Low and moderate elevations in South America east of the Andes
from the Caribbean (including Trinidad) to northern Argentina; Costa
Rica and Panamá in Central America.

Content.—Thirty-one species [synonyms in brackets]: aspera (Peters,
1872); ayeaye (B. Lutz, 1966); bahiana A. Lutz, 1925; bicolor
(Boddaert, 1772) [scleroderma Cope, 1868]; blombergi Funkhouser,
1957; boliviana Boulenger, 1902; buckleyi Boulenger, 1882;
burmeisteri burmeisteri Boulenger, 1882; burmeisteri distincta B.
Lutz, 1950; centralis Bokermann, 1965; cochranae Bokermann, 1966;
coelestis (Cope, 1874); edentula Andersson, 1945; feltoni Shreve,
1935; fimbriata (Miranda-Ribeiro, 1923) [appendiculata A. Lutz,
1925]; guttata A. Lutz, 1925; hypochondrialis (Daudin, 1803)
[azurea Cope, 1862; megacephala (Miranda-Ribeiro, 1926)]; iheringi
Boulenger, 1885; lemur Boulenger, 1882; loris Boulenger, 1912;
medinae Funkhouser, 1962; nicefori Barbour, 1926; orcesi
Funkhouser, 1957; pailona Shreve, 1959; perlata Boulenger, 1882;
rohdei Mertens, 1926 [moschada (Miranda-Ribeiro, 1926)]; sauvagei
Boulenger, 1882 [rickettsii Günther, 1897]; tarsius (Cope, 1868);
tomopterna (Cope, 1868) [palliata Peters, 1872]; trinitatis
Mertens, 1926, vaillanti Boulenger, 1882, venusta Duellmann and
Trueb, 1967.

Remarks.—Phyllomedusa includes 1) a series of large species
(bicolor-burmeisteri) showing progressive specialization of the feet;
2) a series of small species having grasping feet (ayeaye,
centralis, cochranae, guttata, hypochondrialis, and rohdei);
3) a series of small, relatively unspecialized species (lemur,
loris, and medinae); and 4) several other species of questionable
affinities. Lutz (1966) resurrected Cope’s (1866) Pithecopus for 12
species (ayeaye, boliviana, burmeisteri, coelestis,
hypochondrialis, nicefori, rohdei, sauvagei, tarsius,
tomopterna, trinitatis, and vaillanti). Adequate material is not
available for detailed study of all South American species;
consequently, a firm classification cannot be established at this time.
Nevertheless, it is obvious that Lutz’s arrangement is unnatural. If
subsequent investigations show, as seems likely, that the small
specialized phyllomedusines are a natural phyletic unit, the generic
name Pithecopus is available. However, species such as boliviana,
burmeisteri, nicefori, and trinitatis do not belong in
Pithecopus. As noted by Funkhouser (1962), the small, relatively
unspecialized species (lemur, loris, and medinae) form a natural
group; possibly this group should be accorded generic recognition. Until
more evidence on the interspecific relationships is acquired, the
maintenance of the current classification is desirable.

DISCUSSION

Noble (1931) considered the species of Phyllomedusa having opposable
digits, reduced terminal discs, and no webbing to be advanced and such
species as Agalychnis moreleti, calcarifer, and spurrelli to be
primitive. Funkhouser (1957) followed Noble’s suggestion and attempted
to explain the evolution of the species of Phyllomedusa (sensu lato)
by assuming that they evolved from an advanced Hyla-like ancestor.
Therefore, she placed those species having large, fully webbed hands and
feet near the base of her phylogenetic scheme and hypothesized that
evolutionary sequences involved stages of reduction and eventual loss of
webbing, followed by the development of grasping toes. Such an
evolutionary history is highly unlikely. The Agalychnis phyletic line
has one kind of specialization for an arboreal existence. It is contrary
to evolutionary theory that a specialized group would evolve into a
generalized form and then evolve new kinds of specializations to meet
the needs imposed by the same environmental conditions affecting the
earlier specialized group. A more reasonable hypothesis is that the
evolution of opposable digits took place in a phyletic line that had as
its ancestral stock a frog with generalized hands and feet. If this
assumption is correct, Phyllomedusa and Agalychnis represent
different phyletic lines; each exhibits divergent modes of adaptation
for arboreal habits, whereas Pachymedusa probably remains relatively
little changed from the basic phyllomedusine stock.

On the basis of modern distribution and areas of diversification alone
(no fossils are known), it is evident that Phyllomedusa underwent its
adaptive radiation in South America, Agalychnis evolved in Central
America, and Pachymedusa ended up in western México. If we follow the
Matthewsian concepts of the American herpetofauna outlined by Dunn
(1931) and modified by Schmidt (1943) and Stuart (1950), Pachymedusa
represents a “hanging-relict” of a group that moved southward. According
to Savage’s (1966) interpretation of the origins and history of the
American herpetofauna, Agalychnis and Pachymedusa are members of the
Mesoamerican fauna, and Phyllomedusa is part of the Neotropical fauna.
Perhaps the phyllomedusines arose in South America; from there a
primitive stock spread northward and survived as Pachymedusa in
México, whereas the stock in Central America and South America evolved
into Agalychnis and Phyllomedusa, respectively.[Pg 8]

Evidently the primitive phyllomedusines evolved the habit of arboreal
egg deposition and a walking gait; the latter is best developed in the
small, highly specialized species of Phyllomedusa (Lutz, 1966).
Probably the other divergent arboreal adaptations resulted from
environmental stresses and competition. The generalized Pachymedusa
inhabits relatively dry areas characterized by low forest. Throughout
its range it coexists with no more than five other arboreal hylids. The
species of Agalychnis live in rain forests and humid montane forests.
In any given area one species of Agalychnis occurs sympatrically with
no more than a dozen other arboreal hylids. With few exceptions the
species of Agalychnis are more arboreal in their habits than are other
hylids. The species of Phyllomedusa live in the same kinds of habitats
as do those of Agalychnis, but throughout the ranges of most of the
species of Phyllomedusa the diversity of arboreal hylids is much
greater than in Central America. In the upper Amazon Basin as many as 35
hylids occur sympatrically. Many groups of Hyla in this area (for
example, the Hyla boans and Hyla marmorata groups) are equally as
arboreal in their habits as are the species of Agalychnis in Central
America. Conceivably, competition within this array of tree frogs
resulted in selection for modification of the extremities, thereby
bringing about a different mode of climbing in Phyllomedusa. The
walking gait already present in phyllomedusines provided a source for
further modification, which resulted in the development of opposable
digits and the associated lemuroid manner of climbing.

The known life histories of most species of Phyllomedusa, all species
of Agalychnis, and that of Pachymedusa are similar.
Characteristically the tadpoles are generalized pelagic types that
develop in ponds, but at least some of the small specialized
Phyllomedusa in southeastern Brazil have stream-adapted tadpoles with
funnel-shaped mouths (Cochran, 1955; Bokermann, 1966). Knowledge of the
life histories of the other species of Phyllomedusa should aid in the
interpretation of the phylogenetic relationships of the several groups
of frogs now assigned to that genus.

ACKNOWLEDGMENTS

I am grateful to Linda Trueb who provided the osteological data
included, and who helped me in formulating some of the ideas expressed
in the discussion. This paper is a result of investigations on hylid
frogs supported by the National Science Foundation (NSF-GB-5818).

LITERATURE CITED

Bokermann, W. C. A.
1966. A new Phyllomedusa from southeastern Brazil. Herpetologica,
22:293-297.

Cei, J.M.
1963. Some precipitin tests and preliminary remarks on the
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Cei, J.M. and V. Erspamer
1966. Biochemical taxonomy of South American amphibians by means of
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1955. Frogs of southeastern Brazil. Bull. U.S. Natl. Mus., 206; xvi
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1966. The chromosomes of Acris crepitans blanchardi Harper
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1967. Additional studies on chromosomes of anuran amphibians. Syst.
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[Pg 10]

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Transmitted April 18, 1968.