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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 (2_n_=26)
chromosomes. _Acris_ has _n_=11 (2_n_=22) (Cole, 1966). Members of the
_Hyla leucophyllata_, _microcephala_, and _parviceps_ groups have _n_=15
(2_n_=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 (2_n_=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 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

     Phyllomedusidae Günther 1859 [Type genus, _Phyllomedusa_ Wagler,
     1830].

_Definition._--Moderately small to large hylids having vertical pupils,
_n_=13 (2_n_=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.

_Agalychnis_ Cope, 1864 [Type species, _Hyla moreletii_ Duméril, 1853,
by subsequent designation].

_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).


Genus =Pachymedusa=, new genus

Type species, _Agalychnis dacnicolor_ Cope, 1864.

_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

_Phyllomedusa_ Wagler, 1830 [Type species, _Rana bicolor_ Boddaert,
1772].

_Pithecopus_ Cope, 1866 [Type species, _Phyllomedusa azurea_ Cope, 1862
(=_Phyllomedusa hypochondrialis_ Daudin, 1803), by original
designation].

_Hylomantis_ Peters, 1872 [Type species _Hylomantis aspera_ Peters,
1872, by monotypy].

_Phrynomedusa_ Miranda-Ribeiro, 1923 [Type species, _Phrynomedusa
fimbriata_ Miranda-Ribeiro, 1923, by subsequent designation].

_Bradymedusa_ Miranda-Ribeiro, 1926 [Type species, _Bradymedusa
moschada_ Miranda-Ribeiro, 1926 (=_Phyllomedusa rohdei_ Mertens, 1926)
by subsequent designation].

_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.

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

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     1966. Biochemical taxonomy of South American amphibians by means of
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_Transmitted April 18, 1968._