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UNIVERSITY OF KANSAS PUBLICATIONS

MUSEUM OF NATURAL HISTORY


Volume 18, No. 6, pp. 505-545, 7 figs., 4 pls.

December 2, 1969


The Systematics of the Frogs of the
_Hyla rubra_ Group in Middle America



BY

JUAN R. LEÓN



University of Kansas
Lawrence
1969



UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: Frank B. Cross, Philip S. Humphrey, Robert M. Mengel.


Volume 18, No. 6, pp. 505-545, 7 figs., 4 pls.
Published December 2, 1969

UNIVERSITY OF KANSAS
Lawrence, Kansas


PRINTED BY
ROBERT R. (BOB) SANDERS, STATE PRINTER
TOPEKA, KANSAS
1969




The Systematics of the Frogs of the _Hyla rubra_ Group in Middle
America

BY

JUAN R. LEÓN




CONTENTS


                                                    PAGE

INTRODUCTION                                         508
  Acknowledgments                                    508
  Materials and Methods                              509

THE HYLA RUBRA GROUP                                 509
  Key to Species and Subspecies                      510
  Key to Known Tadpoles                              511

ACCOUNTS OF SPECIES AND SUBSPECIES                   511
  _Hyla boulengeri_ (Cope)                           511
  _Hyla foliamorta_ Fouquette                        520
  _Hyla rubra_ Laurenti                              524
  _Hyla elaeochroa_ Cope                             525
  _Hyla staufferi_ Cope                              532
  _Hyla staufferi staufferi_ Cope                    537
  _Hyla staufferi altae_ Dunn                        540

EVOLUTIONARY HISTORY                                 540

LITERATURE CITED                                     543




INTRODUCTION


The tree frogs of the _Hyla rubra_ group are abundant and form a
conspicuous element of the Neotropical frog fauna. Representatives of
the group occur from lowland México to Argentina; the greatest
diversity is reached in the lowlands of southeastern Brazil (Cochran,
1955). The group apparently originated in South America; the endemic
Central American species evolved from stocks that invaded Middle
America after the closure of the Colombian Portal in the late Pliocene.

Dunn (1933) partially defined the _rubra_ group as it occurs in Central
America. Cope (1865, 1876, 1887), Brocchi (1881), Boulenger (1882),
Günther (1901), Noble (1918), Kellogg (1932), Dunn and Emlen (1932),
Stuart (1935), and Gaige (1936) dealt with the Middle American species
now considered to make up the _rubra_ group. More recently, Taylor
(1952, 1958), Fouquette (1958), Starrett (1960), and Duellman (1960,
1963, 1966a) studied aspects of the taxonomy and biology of the species
of this group. The five species of the _rubra_ group in Central America
have received ten different names. One species, _Hyla staufferi_, has
received five names (two subspecies are recognized herein). _Hyla
boulengeri_ was named in the genus _Scytopis_, but the type species of
_Scytopis_ is a member of the genus _Phrynohyas_ Fitzinger, 1843
(Duellman, 1956.)

Little has been published concerning the ecology, life history,
osteology, and mating calls of the Middle American species of this
group. The purpose of the present report is to describe the species
occurring in Middle America and to comment on their distributions,
ecology, cranial osteology, and mating calls, and in so doing provide
evidence for the evolutionary history of the species inhabiting Middle
America.


Acknowledgments

For permission to examine specimens in their care, I am grateful to
Drs. Richard G. Zweifel, American Museum of Natural History (AMNH);
Robert F. Inger, Field Museum of Natural History (FMNH); Ernest E.
Williams, Museum of Comparative Zoology (MCZ); Hobart M. Smith,
University of Illinois Museum of Natural History (UIMNH); Charles F.
Walker, University of Michigan Museum of Zoology (UMMZ); Jay M. Savage,
University of Southern California (USC); James A. Peters, United States
National Museum (USNM); Richard J. Baldauf, Texas Cooperative Wildlife
Collection (TCWC); and W. Frank Blair, Texas Natural History Collection
(TNHC). KU refers to specimens in the Museum of Natural History,
University of Kansas. For the loan of tape-recordings of mating calls I
thank Drs. W. Frank Blair, University of Texas, and Richard G. Zweifel,
American Museum of Natural History.

I am indebted to the Ford Foundation-Universidad de Oriente (Venezuela)
Science Project for a scholarship which enabled me to study for two
years at The University of Kansas, foster institution of the project. I
have benefited by being able to work in the Museum of Natural History
at The University of Kansas and I am grateful to Dr. E. Raymond Hall,
Director, for providing space and equipment.

I gratefully acknowledge the assistance and advice of Dr. William E.
Duellman, who suggested and directed this work, made available
specimens under his care and gave much of his time in reading the
manuscript and suggesting improvements. I am grateful to Dr. Frank B.
Cross who critically read the manuscript and made many editorial
suggestions. I am indebted to Linda Trueb for assistance with the
osteological aspects of this study; she helped to clarify many
confusing points. I am grateful to Charles W. Myers for making
available his field notes on these frogs in Panamá, to Arthur C.
Echternacht for reading part of the manuscript, and to John D. Lynch
for many suggestions and helpful criticisms. The illustrations were
executed by David M. Dennis.


Materials and Methods

For the purposes of the present study I examined 1383 preserved
specimens, 50 skeletons, and 9 lots of tadpoles. External
characteristics used in the analysis of variation are those currently
employed in the study of anuran systematics. Twelve measurements
and six proportions were taken in the manner described by Duellman
(1956). Only the most important references are given in the synonymies,
except those of the two subspecies of _Hyla staufferi,_ which are
more nearly complete. The taxonomic history of each frog is discussed
under _Remarks_ in each account. The cranial osteology was studied
by using skeletons and cleared and stained specimens of all species.
Developmental stages of tadpoles were determined from Gosner's (1960)
table. Personal field work in Central America in the summer of 1966
provided an opportunity to make observations on the ecology, calling
sites, and color in life; these data were supplemented by field notes
from, and discussions with, Dr. William E. Duellman and Charles W.
Myers.

The mating calls of the frogs were recorded in the field on Magnemite
and Uher Tape Recorders by Dr. Duellman in the course of his work on
the hylid frogs of Middle America--supported by grants from the
National Science Foundation (G-9827 and GB-1441). These recordings,
plus those borrowed from other institutions, provided 50 tapes for
analysis of the mating calls. The calls were analyzed on a Vibralyzer
(Kay Electric Company).




THE HYLA RUBRA GROUP


_Definition._--The species forming the group are small to moderate-sized
tree frogs (maximum snout-vent length of males of various species 20-49
mm.), distinguished from other groups in the genus _Hyla_ as follows:
Brown, grayish brown, or yellowish tan above; thighs plain, marbled
with dark brown, or having vertical bands; vocal sac single, median,
subgular; snout flat, protruding, rounded or pointed; webbing between
fingers reduced or absent; web between first and second toes reduced to
fringe on second toe, rest of toes about half webbed; tarsal fold
reduced or absent; shanks robust; inner metatarsal tubercle larger than
outer; prevomerine teeth on transverse ridges between small to large
sized choanae; skull generally longer than wide; nasals large (length
more than 40 per cent total length of skull) and having pointed
maxillary processes; maxillary bearing small ventromedial palatine
process; quadratojugal slender, always joined to maxillary by bony
suture; auditory region of proötic slender and short; delicate
spatulate columella ventral to crista parotica, broad basally,
compressed anterolaterally, slightly rounded distally; anterior arm of
squamosal extending about half distance to maxillary; sphenethmoid
wider than long; frontoparietal fontanelle present or absent;
prevomerine, premaxillary, and maxillary teeth present; prevomer with
two lateral processes forming incomplete bony margin to internal nares;
tadpoles having pointed xiphicercal tail, snout short, rounded; 2/3
tooth rows; dorsal fin deeper than ventral fin; sinistral spiracle;
short dextral anal tube not reaching edge of ventral fin; mating calls
consisting of single long note or series of short notes.

_Composition._--This group contains about 24 currently recognized
species, most of which occur in Brazil. Only five species--_boulengeri,_
_elaeochroa_, _foliamorta_, _rubra_, and _staufferi_ with two
subspecies--occur in Central America. _Hyla boulengeri_ and _rubra_ are
widespread in South America, and _foliamorta_ occurs in Colombia,
whereas the other species are known only from Middle America.

_Distribution._--The species of the _Hyla rubra_ group range from the
lowlands of northern Argentina and Bolivia to southern Tamaulipas and
Guerrero, México.

_Comments._--In Central America two subgroups of species can be
recognized. _Hyla boulengeri_ and _H. foliamorta_ are distinctive in
the large size of adults (snout-vent lengths 41-49 mm.); both have
prominent bars on the thighs, a well-defined interorbital triangular
mark, blotches or spots dorsally, and large choanae. _Hyla elaeochroa,_
_H. rubra,_ and _H. staufferi_ are smaller (snout-vent lengths 29-40
mm.); they have the thighs weakly barred or vermiculate anteriorly and
posteriorly or unmarked, an ill-defined interorbital triangular mark,
linear markings dorsally, and small choanae.


Key to Species and Subspecies

    1. Larger frogs (males to 49 mm. snout-vent length); thighs
    strongly barred; supratympanic fold black; dorsum blotched or
    spotted                                                         2

    Smaller frogs (males to 40 mm. snout-vent length); thighs weakly
    barred or plain; supratympanic fold pale brown; dorsum usually
    having linear pattern                                           3

    2. Dorsum tuberculate; snout subacuminate; vocal sac flecked with
    brown; tarsal fold rudimentary; web absent between fingers; black
    spots absent in scapular region                   _H. boulengeri_

    Dorsum smooth; snout pointed; vocal sac dark gray; tarsal fold
    absent; trace of web between fingers; two or more elongate dark
    spots in scapular region                          _H. foliamorta_

    3. Snout-vent length more than 30 mm.; tympanum 2/3 to 3/4 diameter
    of eye; prevomerine elevations about size of choanae            4

    Snout-vent length less than 30 mm.; tympanum less than 1/2 diameter
    of eye; prevomerine elevations smaller than choanae             5

    4. Thighs mottled posteriorly; discs on fingers about 1/2 size of
    tympanum; faint dark line from nostril to eye          _H. rubra_

    Thighs faintly barred or plain posteriorly; discs on fingers
    about size of tympanum; distinct dark line from nostril to eye
                                                      _H. elaeochroa_

    5. Dorsum brown with irregular dorsolateral stripes and
    interrupted paravertebral stripes; two transverse bars on shanks;
    interorbital bar present                 _H. staufferi staufferi_

    Dorsum gray with complete dorsolateral and paravertebral stripes;
    longitudinal stripe on shank; interorbital bar absent
                                                 _H. staufferi altae_


Key to Known Tadpoles

    1. Entire lower beak black; beaks moderate-sized, serrate; dorsal
    fin high, extending to middle of back                           2

    No more than half of lower beak black; beaks small, finely serrate;
    dorsal fin lower, barely extending onto body                    3

    2. Papillae present only laterally                _H. boulengeri_
    Papillae present laterally and ventrally          _H. foliamorta_

    3. Distinct brown stripe from nostril to eye; two stripes below
    eye,                                              _H. elaeochroa_

    Faint stripe from nostril to eye; no stripe below eye
                                                       _H. staufferi_




ACCOUNTS OF SPECIES AND SUBSPECIES


_Hyla boulengeri_ (Cope)

    _Scytopis boulengeri_ Cope, Bull. U.S. Natl. Mus., 32:12, December
    1, 1887 [Holotype.--USNM 13974, from "Nicaragua"; J. A. McNiel,
    collector].

    _Hyla boulengeri:_ Günther, Biologia Centrali-Americana, Reptilia
    and Batrachia, p. 267, June 1901. Noble, Bull. Amer. Mus. Nat.
    Hist, 38:339, June 1918. Taylor, Univ. Kansas Sci. Bull., 35:856,
    July 1, 1952.

_Diagnosis._--Size large (Male to 49 mm., Female to 53 mm.); skull as
long as wide; frontoparietal fontanelle present; snout subacuminate;
canthus not pronounced; choanae large; tongue cordiform, slightly
longer than broad; interorbital triangle tubercular; skin on dorsum
tuberculate; tarsal fold reduced or absent; thighs, shanks, and tarsi
boldly barred with dark brown and pale yellow-green in life.

_Description._--Head flattened, longer than wide; snout projecting
beyond lower lip; loreal region oblique; canthus not pronounced; length
of eye less than interorbital distance; tympanum large, about 70 per
cent of diameter of eye; interorbital triangle distinct; arms short;
fingers lacking web; palmar tubercle tripartite; subarticular tubercles
distinct; long tubercle on base of first finger; discs truncate; legs
long; tarsal fold reduced or absent; inner metatarsal tubercle rounded,
larger than outer, both elevated; subarticular tubercles distinct; one
phalanx free of web on second, third, and fifth toes, three free on
fourth toe (Fig. 1A and B); skin tuberculate on dorsum, less so on
flanks; skin of belly granular, that on chest and throat weakly
granular; tongue cordiform, longer than wide, free and notched behind;
vocal slits large, lateral to tongue.

  [Illustration: Fig. 1. A and B.--Hand and foot of _Hyla boulengeri_
  (KU 102173), × 3. C and D.--Hand and foot of _Hyla s. staufferi_× (KU
  57790), × 6]

In life, dorsum tan or brown with dark spots on snout, head, and
scapular region; interorbital triangle and blotch posteriorly on dorsum
dark brown; flanks pale green; groin pale green or orange, mottled with
dark brown; thighs tan or brown above with dark transverse bars on
anterior and posterior surfaces; spaces between bars green or orange;
inner surfaces of shanks and outer surfaces of tarsi brown and orange;
foot brown above; forelimbs brown and pale green above, weakly barred;
belly creamy white with scattered brown spots; vocal sac creamy white
flecked with brown; lower jaw brown with white spots on lips (Pl. 1A).

In preservative, head and dorsum dark brown with triangular spot
between eyes; dark spots on head and scapular region and dark brown
blotch posteriorly on dorsum; flanks creamy white with brown spots;
groin creamy white mottled with dark brown; thighs brown above with
dark brown transverse bars on anterior and posterior surfaces; inner
surfaces of shanks and outer surfaces of tarsi barred with pale brown;
dorsal surface of foot mottled brown and creamy white; ventral surface
of foot and toes pale brown; forelimbs faintly barred with pale brown;
belly white with a few pale brown spots; vocal sac flecked with pale
brown; lower jaw marked with small white spots on lips.

_Variation._--Geographic variation is evident in the snout-vent length,
tibia length, and foot length, all in relation to snout-vent length,
and the relative size of the tympanum to the eye (Table 1). The largest
specimens are from the humid Pacific lowlands of Costa Rica;
individuals from the Caribbean lowlands of Costa Rica, Canal Zone, and
South America are smaller. A general trend for increase in size extends
from South America to the Pacific lowlands of Costa Rica.

Most variation in color does not seem to be correlated with geography;
color variation is nearly as great within a given population as between
separated populations. However, most specimens from Rincón de Osa,
Puntarenas Province, Costa Rica, are dusky brown, but a few are darker.
In comparison with specimens from the Caribbean lowlands of Central
America, specimens from the Pacific slopes in Costa Rica have a darker
interorbital triangle. In some specimens from the latter area
rugosities are present on the borders of the interorbital triangle, on
the snout, on the upper eyelid, and on the heel. Specimens from the
Caribbean lowlands are less tuberculate, and most individuals from
there lack rugosities on the tarsus. Living individuals from Puerto
Viejo, Heredia Province, Costa Rica, and from the Canal Zone, Panamá,
are brown above with a metallic green tint. Rugosities are present on
the posterior edges of the forelimbs in some specimens from throughout
the range. In most respects, specimens from the Canal Zone resemble
those from the Caribbean lowlands of Costa Rica more than they resemble
those from the Pacific lowlands of Costa Rica, but some individuals
from the Canal Zone are less metallic above and have small white spots
dorsally on the body, head, and limbs.

A moderate amount of color change from night to day has been noted. At
night, a male from Puerto Viejo, Heredia Province, Costa Rica, was
grayish tan above with slightly darker markings; the flanks were pale
yellowish green. By day, the dorsum was brown with darker markings, and
the throat was pale gray with white flecks; the rest of the venter was
creamy white. The groin was pale green with black mottling; the
anterior and posterior surfaces of the thighs and inner edges of the
tarsi were greenish yellow with black bars.

TABLE 1.--Geographic Variation in Size and Proportions in Males of
_Hyla boulengeri_. (Means in parentheses below observed ranges.)

=========================================================================
                    |    | Snout-vent|   Tibia   |         |
                    |    |  length   |   length/ |Tympanum/|Foot length/
Locality            |  N |   (mm.)   | snout-vent|   eye   | snout-vent
--------------------+----+-----------+-----------+---------+-------------
Costa Rica: Tilarán | 23 | 37.4-48.7 | 0.52-0.58 |0.62-0.76| 0.39-0.45
                    |    |   (43.8)  |  (0.55)   | (0.71)  |  (0.42)
                    |    |           |           |         |
Costa Rica: Rincón  | 10 | 41.4-46.1 | 0.54-0.60 |0.68-0.80| 0.40-0.45
  de Osa            |    |   (44.0)  |  (0.57)   | (0.74)  |  (0.43)
                    |    |           |           |         |
Costa Rica: Alajuela| 13 | 35.6-43.1 | 0.55-0.60 |0.63-0.78| 0.41-0.46
  Province          |    |   (39.8)  |  (0.57)   | (0.69)  |  (0.44)
                    |    |           |           |         |
Costa Rica: Puerto  | 25 | 37.5-42.9 | 0.51-0.62 |0.63-0.79| 0.38-0.46
  Viejo             |    |   (41.6)  |  (0.55)   | (0.71)  |  (0.43)
                    |    |           |           |         |
Costa Rica: Suretka |  9 | 38.7-42.0 | 0.56-0.58 |0.53-0.72| 0.35-0.45
                    |    |   (41.0)  |  (0.56)   | (0.62)  |  (0.42)
                    |    |           |           |         |
Panamá: Canal Zone  | 16 | 36.7-42.9 | 0.52-0.58 |0.70-0.78| 0.40-0.44
                    |    |   (39.0)  |  (0.54)   | (0.74)  |  (0.42)
                    |    |           |           |         |
Venezuela: Santomé  |  4 | 35.5-40.9 | 0.45-0.48 |0.63-0.67| 0.36-0.40
                    |    |   (38.5)  |  (0.46)   | (0.65)  |  (0.38)


TABLE 2.--Comparison of Mating Calls in the _Hyla rubra_ Group. (Means
in parentheses below observed ranges.)

============================================================================
               |   |Notes|        |       |           |  Major frequencies
               |   | per |Duration| Pulses|Fundamental|       (cps)
               |   |call | of note|  per  | frequency |---------------------
Species        | N |group| (sec.) | second|  (cps)    |  Lower  |  Upper
---------------+---+----+---------+-------+-----------+---------+-----------
H. boulengeri  | 8 |   1 | 0.24-  | 80-120|  70-74    |1400-1820|2520-3182
               |   |     | 0.47   |  (101)|   (71)    |  (1611) | (2840)
               |   |     | (0.35) |       |           |         |
               |   |     |        |       |           |         |
H. foliamorta  | 7 |   1 | 0.23-  | 50-60 |  52-61    | 912-1026|2736-3477
               |   |     | 1.86   |  (51) |   (56)    |  (918)  | (3055)
               |   |     | (0.69) |       |           |         |
               |   |     |        |       |           |         |
H. elaeochroa  |15 | 2-95| 0.12-  | 40-50 |  48-65    |1254-1586|2562-3477
               |   | (19)| 0.24   |  (42) |   (57)    |  (1499) |  (2911)
               |   |     | (0.17) |       |           |         |
               |   |     |        |       |           |         |
H. s. staufferi|18 | 2-77| 0.13-  |100-130|  96-130   |1582-1872|1962-3744
               |   | (23)| 0.23   | (120) |   (106)   |  (1743) |  (3056)
               |   |     | (0.18) |       |           |         |
               |   |     |        |       |           |         |
H. s. altae    | 7 | 2-22| 0.14-  |110-130| 104-117   |1853-2106|3379-4056
               |   | (11)| 0.18   | (120) |   (112)   |  (2008) |  (3775)
               |   |     | (0.15) |       |           |         |

_Cranial Osteology._--The skull of _Hyla boulengeri_ is as long as it
is wide, and is flat; the premaxillary is small and bears 13 to 17
teeth (mean for 6 specimens, 14.9). The alary processes of the
premaxillaries are widely separated, concave posteriorly, and vertical.
Ventrally, the premaxillary is connected to the prevomer by bony
tissues. The maxillary is slender and bears 70 to 91 teeth (mean for 6
specimens 78.1). The pars facialis of the maxillary is laterally convex
and about four times as high as the pars dentalis.

The nasal is large (its length about 40 per cent of total length of
skull), and pointed anteriorly and posteriorly in dorsal view. The
nasals are separated anteromedially by the cartilaginous septum nasi.
One or two protuberances are present on the midlateral concavity of the
nasal. Posteriorly, the nasal overlaps the sphenethmoid and articulates
with the palatine. Dorsally the sphenethmoid is large, pentagonal, and
completely ossified. The frontoparietal is elongate, smooth, and bears
a small supraorbital process on the anterior edge of the orbit. A
keyhole-shaped frontoparietal fontanelle is present; the fontanelle is
narrow anteriorly and wide posteriorly.

The bony part of the proötic is separated dorsally from the squamosal
by the cartilaginous crista parotica. The squamosal is small, its
anterior arm slender and pointed. The posterior arm of the squamosal is
pointed terminally and articulates with the proötic medially.

The prevomer is large and elongate. Anteriorly the prevomer is
connected to the maxillary-premaxillary articulation; posteriorly, the
prevomer is separated from the sphenethmoid by cartilage. Each prevomer
bears six to nine teeth. The palatine is present and edentate. The
anterior end of the parasphenoid is broad (less pointed than in _Hyla
foliamorta_). The pterygoid is slender and well developed.

_Natural History._--_Hyla boulengeri_ inhabits humid lowland tropical
forests and breeds in temporary ponds. Clasping pairs and gravid
females were observed at Puerto Viejo, Heredia Province, Costa Rica, on
June 21, 1966. Males were calling from depressions in decaying logs and
stumps, in forked stems, and from leaves of broad-leafed plants near
the pond. Males were observed in late July and early August calling
from _Calathea_ and _Heliconia_ leaves at the edge of a pond in the wet
forest of the Osa Peninsula. William E. Duellman informed me that he
collected calling males in January at El Real, Darién, and in March at
Almirante, Bocas del Toro, Panamá. Taylor (1952) found calling males in
June at Turrialba, Cartago Province, Costa Rica, and Dunn (1931a)
observed males calling in July, November, and December in Panamá.
Gravid females have been found from April to August. Breeding
activities of _Hyla boulengeri_ always seem to be associated with
temporary ponds; in Central America breeding apparently takes place
throughout most of the year.

The mating call of _Hyla boulengeri_ consists of one short, moderately
low-pitched note. Each note has a duration of 0.24 to 0.47 second and
is repeated at intervals of one second to several minutes. The notes
have 80 to 120 pulses per second, a fundamental frequency of about 70
cycles per second, and a dominant frequency of 2,840 cycles per second
(Table 2, Pl. 3A).

The eggs are deposited in a mass in the water. No information is
available concerning early development. Tadpoles in advanced stages of
development were found in a temporary pond at Rincón de Osa, Puntarenas
Province, Costa Rica. The pond was about 10 cm. deep, had a muddy
bottom and lacked vegetation. Three recently metamorphosed young were
found in mid-August, 1966, on grass at the edge of another temporary
pond in the forest.

_Tadpoles_--Twelve tadpoles are available. These were collected at
Rincón de Osa, Puntarenas Province, Costa Rica. The maximum size
represented is 34.0 mm., total length (stage 42 of development).

A typical tadpole in stage 36 of development (KU 104295) has a body
length of 12.0 mm., tail length of 20.0 mm., and total length of 32.0
mm. Other characters are as follows: depth of tail equal to length of
body; body deeper than wide; distance between eye and nostril equal to
that between nostril and tip of snout; mouth anteroventral, upper and
lower lips bare; papillae present laterally; tooth rows 2/3; upper rows
about equal in length; first upper row slightly, and second upper row
widely, interrupted medially; lower rows about equal in length, shorter
than upper rows; third lower row containing 5-10 large teeth; beak
strong, serrate; spiracle nearer anus than eye; anal aperture not
extending to border of ventral fin; caudal musculature slender
posteriorly, extending to tip of pointed tail; dorsal fin extending to
middle of body, slightly deeper than ventral fin; posterior three
fourths of tail spotted; rest of tail and body gray-brown or
transparent; hindlimbs flecked or spotted with brown (Table 3, Fig. 2A
and 3A).

TABLE 3.--Sizes of Tadpoles of _Hyla boulengeri_ in Relation to
Developmental Stages. (Means in parentheses below observed ranges;
measurements in mm.)

    =======================================================
    Stage   | N | Body length | Tail length | Total length
    --------+---+-------------+-------------+--------------
      30    | 1 |     11.0    |     22.2    |     33.2
            |   |             |             |
      35    | 1 |     11.0    |     12.0    |     23.0
            |   |             |             |
      36    | 3 |   9.5-12.0  |  20.0-21.5  |  31.0-32.0
            |   |    (11.2)   |    (20.5)   |    (31.7)
            |   |             |             |
      38    | 2 |     11.5    |     22.0    |     33.5
            |   |             |             |
      42    | 2 |  10.5-13.0  |  21.0-22.0  |  32.5-34.0
            |   |    (11.8)   |    (21.5)   |    (33.3)
            |   |             |             |
      44    | 2 |  14.0-15.0  |   8.0-15.0  |  22.0-30.0
            |   |    (14.5)   |    (12.5)   |    (26.0)
            |   |             |             |
      46    | 1 |     15.0    |     15.0    |

A recently metamorphosed young has a snout-vent length of 15 mm.; the
head is as long as wide, the eyes are prominent; the limbs are weakly
barred; the skin is rugose above and granular below. The venter is
immaculate; the dorsum and limbs are gray-brown in preservative (pale
green in life). The interorbital space, supratympanic fold, and
scapular region are darker than the rest of the body; the fingers lack
webbing; the webbing on the foot is the same as in adults; small
metatarsal tubercles are present, but the tarsal fold is absent.

  [Illustration: Fig. 2. Tadpoles of (A) _Hyla boulengeri_ (KU 104295)
  and (B) _Hyla elaeochroa_ (KU 104134), × 3.]

  [Illustration: Fig. 3. Mouthparts of tadpoles of (A) _Hyla
  boulengeri_ (KU 104295) and (B) _Hyla elaeochroa_ (KU 104134), × 25.]

_Remarks._--Cope (1887:12) described _Scytopis boulengeri_ from
Nicaragua. Günther (1901:267) placed _boulengeri_ in the genus _Hyla_,
and stated that Cope possibly placed _boulengeri_ in the genus
_Scytopis_ on the supposition that it had an accumulation of
"sebaceous glands" above the tympanum. Noble (1918:339) redescribed
_Hyla boulengeri_ on the basis of three specimens from Zelaya
Province, Nicaragua, and noted that the glands were not prominent in
any of the specimens. Duellman (1956:8) showed that _Scytopis hebes_
(generotype of _Scytopis_ by monotypy) is a Phrynohyas, and thus
placed _Scytopis_ Cope, 1862, in the synonymy of _Phrynohyas_
Fitzinger, 1843.

Dunn and Emlen (1932:25) placed _Hyla lancasteri_ Barbour in the
synonymy of _Hyla boulengeri_; the former was known solely from one
juvenile. They made no qualifying statements, but probably they were
impressed by the strongly barred thighs, a coloration known among
Central American hylids at that time only in _Hyla boulengeri_
(Duellman, 1966a:271). Taylor (1952:856) followed Dunn and Emlen with
reservation and noted some differences. Duellman (1966a:271) showed
that the holotype of _lancasteri_ was a juvenile of a species
subsequently named as _Hyla moraviaensis_ by Taylor (1952:865).

In Central America, _Hyla boulengeri_ can be confused only with _Hyla
foliamorta;_ the latter is restricted to central and eastern Panamá
and northern Colombia. The snout of _foliamorta_ is more pointed and
protruding, and the vocal sac is darker than in _boulengeri_; the
groin of _foliamorta_ usually is creamy white, whereas _boulengeri_
usually has a dark spot. The skulls differ in that _boulengeri_ has a
frontoparietal fontanelle, the prevomer is larger and elongate,
anteriorly connected to the premaxillary, and posteriorly separated
from the sphenethmoid by cartilage; _foliamorta_ lacks a fontanelle,
the prevomer is smaller, anteriorly separated from the premaxillary by
cartilage, but connected by a bony suture to the sphenethmoid. The
mating call of _boulengeri_ differs by having shorter notes, twice as
many pulses per second, a higher fundamental frequency, and more
closely approximated major frequencies than does that of _foliamorta_.

_Hyla boulengeri_ need not be compared in detail with the other Central
American members of the _Hyla rubra_ group, because all of them are
smaller and have shorter snouts, smoother skin, and dissimilar color
patterns.

_Distribution._--In Central America _Hyla boulengeri_ inhabits the
forested lowlands in locally humid areas in Guanacaste Province, Costa
Rica, and in the humid Golfo Dulce region of Costa Rica; it occurs on
the Carribbean lowlands from central Nicaragua to South America, where
it ranges to Guyana and Ecuador. The highest elevations where _H.
boulengeri_ has been found are 620 meters at Turrialba, Cartago
Province, and 700 meters at Tilarán, Guanacaste Province, Costa Rica
(Fig. 4).

_Specimens Examined._--Costa Rica: _Alajuela_: 9 km N Ciudad Quesada,
near La Florencia, USC 8059 (4); 18 km N Florencia, USC 2624; Laguna
Monte Alegre, KU 64334; Las Playuelas, 11 km S Los Chiles, USC 7216,
7217 (2), 7219; 3 km NE Muelle del Arenal, USC 2644 (5). _Cartago_:
Turrialba, KU 24741. _Guanacaste_: 7 km N Liberia, USC 8096 (2), 8138
(6); 13.6 km N Liberia, USC 8151, 8171 (2); 20.5 km S Liberia, USC
8205; Taboga, 20 km SE Las Cañas, KU 102170, USC 7166; 4 km NE Tilarán,
USC 8023; 6 km NE Tilarán, USC 523 (3), 6262, 7019. _Heredia_: Puerto
Viejo, KU 64323-7 (skeletons), 104351-3 (skeletons), 64330-3,
103592-620; 1 km NE Puerto Viejo, UMMZ 126042; 1 km S Puerto Viejo, KU
84983-4 (skeletons), 86317-22, 87774 (skeleton); 4.2 km W Puerto Viejo,
KU 64329, 64328 (skeleton). _Limón_: Mountain Cow Creek, near Banano,
KU 37031, 41067 (skeleton); 3 km S Río Tortuguero, AMNH 69057; Suretka,
KU 36482-8, 36699. _Puntarenas_: 4.8 km S Bahía Rincón on NW side Río
Rincón, USC 705; Parrita, USC 6163; 4.5 km W Rincón de Osa, KU
102177-9, 104295-6 (tadpoles); 6 km SW Rincón de Osa, KU 102171-6; 4.4
km NW Villa Neilly, USC 8003; 10.5 km WNW Villa Neilly, KU 64321. _San
José_: 21 km WSW San Isidro el General, KU 34104-6.

  [Illustration: Fig. 4. Map showing locality records for _Hyla
  boulengeri_ (circles) and _H. foliamorta_ (dots).]

Panamá: _Bocas del Toro_: 3.2 km W Almirante, KU 95978. _Canal Zone_:
Barro Colorado Island, FMNH 13379; near Clayton Reservation, UIMNH
42000; 2.6 km SW Fort Kobbe, KU 95977; Miraflores Locks, AMNH 69764-5;
Summit, AMNH 73445, KU 97777, 101540-9, 104350 (skeleton). _Colón_: Río
Gatuncillo, near Nuevo San Juan, KU 95976. _Darién_: El Real, KU
80451-3.


_Hyla foliamorta_ Fouquette

    _Hyla foliamorta_ Fouquette, Herpetologica, 14:125, April 25,
    1958 [Holotype.--TNHC 23109, 11 km. NW Miraflores Locks, Canal
    Zone, Panamá; M. J. Fouquette, Jr. collector].

_Diagnosis._--Size medium (Male to 43 mm., Female to 41 mm.); skull
longer than wide; frontoparietal fontanelle absent; snout acuminate,
projecting; interorbital triangle bordered by white lines; scapular
region having two or more elongate spots; dorsum smooth; vocal sac
dark gray; groin creamy white; traces of web between fingers.

_Description._--Head flattened, longer than wide; snout flat, pointed,
protruding beyond lower lip; loreal region slightly concave; canthus
moderately prominent; eyes smaller than interorbital space; tympanum
distinct, 55 to 75 per cent of diameter of eye, smaller than
internarial space; arms short; fingers having rudimentary webs; median
palmar tubercle tripartite; inner palmar tubercle on base of first
finger flat; subarticular tubercles distinct; discs of fingers smaller
than diameter of tympanum; legs long; tarsal fold lacking; inner
metatarsal tubercle larger than outer; one phalanx free on second,
third, and fifth toes, two and one half phalanges free on fourth toe;
narrow fringe continuing from web to discs of toes; discs of toes
about the size of those on fingers; skin smooth on dorsum and flanks,
that on belly and posterior part of thighs granular; tongue oval,
longer than wide; vocal slits oblique, about one half length of
tongue.

In life, dorsum pale tan to pale reddish brown with irregular reddish
brown markings; small dark spots on head; distinct dark brown
triangular mark between eyes, bordered by thin white lines; apex of
triangle always directed backward; supratympanic fold with black edge;
scapular region having two to five small, elongate black spots; belly
creamy tan with small brown spots; vocal sac uniformly dark brown with
scattered creamy tan flecks; upper jaw dark brown; limbs creamy white
below with scattered brown spots; groin marked with small brown spots
in some specimens; anterior and posterior surfaces of thighs
yellow-orange with three distinct black blotches; two dark bands on
upper surface of shanks; webbing of feet yellowish tan with brown
mottlings (Pl. 1B).

In preservative, dorsum brown or gray with darker markings; interorbital
triangle distinct, bordered by white lines; supratympanic fold with
black edge; two or more small elongate black spots in scapular region;
belly white with numerous brown flecks; edge of upper lip dark brown;
vocal sac dark gray; undersides of limbs creamy white; groin creamy
white with or without brown spots; anterior and posterior surfaces of
thighs having three black blotches separated by creamy white spaces;
shanks having two brown bands; webbing of feet mottled with brown.

_Variation._--Twenty-eight breeding males from the area between Chepo
and Tocumen, Panamá, have snout-vent lengths of 39.0 mm. to 46.0 mm.
(mean 42.5 mm.). In these specimens, the ratio of the tibia length
to the snout-vent length is 0.54 to 0.61 (mean, 0.57); the ratio
of the diameter of the tympanum to that of the eye is 0.55 to 0.75
(mean, 0.67). One female has a snout-vent length of 41.0 mm.,
tibia/snout-vent length ratio of 0.57, and tympanum/eye ratio of 0.76.
Two to five (usually three) elongate black spots are present in the
scapular region in different individuals. The flanks in some are
spotted with brown; in others they are creamy white. A small black
spot is present in the groin of some specimens. Usually two to four
blotches are present on the anterior and posterior surfaces of the
thighs; in some specimens the blotches are reduced to small spots. One
or two brown spots are present proximally on the shanks in most
specimens. In some individuals tuberculations are scattered on the
head and in the tympanic and scapular regions, but the dorsum is
smooth in most specimens; the belly is creamy white flecked with
brown.

_Cranial Osteology._--The skull of _Hyla foliamorta_ is flat and
longer than it is wide. The premaxillary is small and bears 13 to 16
teeth (mean for 2 specimens, 14.8). The alary process of the
premaxillary is vertical and concave posteriorly. Ventrally, the
premaxillary is completely separated from the prevomer by cartilage.
The maxillary is slender; each bears 77 to 84 teeth (mean for 2
specimens, 81). The pars facialis of the maxillary is laterally convex
and less than three times the height of the pars dentalis.

The nasal is large and pointed anteriorly and posteriorly in dorsal
view. The length of the nasal comprises about 40 per cent of the total
length of the skull. The nasals are separated anteromedially by the
cartilaginous septum nasi. One protuberance is present on the
midlateral concavity of the nasal. Posteriorly, the nasal overlaps the
sphenethmoid; posterolaterally the nasal articulates with the
palatine. The sphenethmoid is completely ossified and pentagonal in
dorsal view. The frontoparietal is elongate, without a pronounced
anterior supraorbital process. The frontoparientals are sutured
medially throughout their lengths; the frontoparietal fontanelle is
absent.

The bony part of the proötic is narrowly separated dorsolaterally from
the squamosal by the cartilaginous crista parotica. The squamosal is
large; the anterior arm is pointed. The posterior arm of the squamosal
is broad, rounded terminally, and articulates with the proötic
medially.

The prevomer is short and separated anteriorly from the premaxillary
and maxillary by cartilage. The posterior margin of the prevomer has a
bony articulation with the sphenethmoid. Each prevomer bears five to
seven teeth. The palatine is small and edentate. The anterior end of
the parasphenoid is narrow (more pointed than in _Hyla boulengeri_).
The pterygoid is slender and well developed (Fig. 5A).

  [Illustration: Fig. 5. Dorsal views of the skulls of (A) _Hyla
  foliamorta_ (KU 77687) and (B) _H. elaeochroa_ (KU 68289), × 3.]

_Natural History._--_Hyla foliamorta_ inhabits lowland forests in
eastern Panamá and breeds in temporary ponds. Males have been observed
calling from grasses, bushes, and emergent vegetation near temporary
ponds and ditches along roads. William E. Duellman informed me that he
found a breeding congregation of this species in June near Chepo,
Panamá, where males were calling from spiny palms at the edge of a
woodland pond. Fouquette (1958) found calling males in May, August,
and September near Miraflores Locks, Canal Zone. Calling stations vary
from one to two meters above ground. No clasping pairs have been
found; only one female is known (KU 101589, from 8 km NE Tocumen,
Panamá); this gravid individual was collected in early June.

The mating call of _Hyla foliamorta_ consists of one pulsed,
low-pitched, moderate trill of about O.5 second duration. Each note is
repeated at intervals of 5 seconds to a few minutes. The notes have
about 50 pulses per second, a fundamental frequency of 56 cycles per
second and a dominant frequency of about 3000 cycles per second (Table
2, Pl. 3B).

Egg deposition sites are unknown. No information is available
concerning early development, and little is known about the breeding
season of _Hyla foliamorta_. Probably its breeding activities are
restricted to the rainy months.

_Tadpoles._--Eight tadpoles were collected from a weedy temporary pond
near Chepo, Panamá, in early June.

A typical tadpole in stage 35 of development (KU 104244) has a body
length of 9.5 mm., tail length of 25.0 mm., and a total length of 34.5
mm. Other characters are as follows: depth of tail equal to length of
body; body deeper than wide; distance between eye and nostril equal to
distance between eye and spiracle; mouth anteroventral; median part of
upper lip bare; rest of lip having one row of papillae; a few other
rows of small papillae at corners of mouth; tooth rows 2/3; first
upper row entire, second upper row interrupted medially, shorter than
first; lower rows shorter than upper rows, third shortest; beak
moderately robust; spiracle nearer eye than anus; anal tube short,
aperture not extending to border of ventral fin; caudal musculature
slender, extending to tip of pointed tail; dorsal fin extending onto
body (Table 4).

TABLE 4.--Sizes of Tadpoles of _Hyla foliamorta_ in Relation to
Developmental Stages. (Means in parentheses below observed ranges;
measurements in mm.)

    =======================================================
    Stage   | N | Body length | Tail length | Total length
    --------+---+-------------+-------------+--------------
      25    | 2 |   5.0-5.2   |   8.0-8.5   |  13.0-13.7
            |   |    (5.1)    |    (8.3)    |    (13.4)
            |   |             |             |
      26    | 3 |   7.0-7.5   |  12.0-12.4  |  17.0-19.5
            |   |    (7.2)    |   (12.1)    |    (18.6)
            |   |             |             |
      28    | 2 |   6.5-7.0   |    18.0     |     25.0
            |   |    (6.8)    |             |
            |   |             |             |
      35    | 1 |     9.5     |    25.0     |     34.5

In life, yellow above, white below; caudal fin greenish yellow with
black or gray reticulations; dark line from snout to eye; dark spot
behind eye; tail unpigmented except for fine dark reticulations. In
preservative body creamy white, transparent below with dark pigment
above in some specimens.

_Remarks._--_Hyla foliamorta_ can be confused only with _Hyla
boulengeri_. The differences between adults of these species were
discussed in _Remarks_ on _H. boulengeri_. The tadpoles of
_foliamorta_ have labial papillae on the lower lip and a stripe
between the eye and the tip of the snout. By comparison the tadpoles
of _boulengeri_ have a bare lower lip and no stripe between the eye
and the tip of the snout.

_Distribution._--_Hyla foliamorta_ inhabits the subhumid Pacific
lowlands (elevations of less than 100 meters) of Central Panamá and
Caribbean lowlands of northern Colombia (Fig. 4).

_Specimens Examined._--Panamá: _Panamá_: 3 km WSW Chepo, KU 77164-9,
101573-5, 104243-4 (tadpoles); 6 km WSW Chepo, KU 77170, 101576-8; 1.5
km SW Naranjal, KU 77171, 77687 (skeleton); 2 km N Tocumen, KU
101579-83, 104349 (skeleton); 8 km NE Tocumen, KU 101584-92.

No specific locality: TNHC 24401.


_Hyla rubra_ Laurenti

    _Hyla rubra_ Laurenti, Synopsis Reptilium Emendatum, p. 35, 1768.
    Daudin, Hist. Nat. Rainettes Grenouilles Crapauds, II:26, 1802.
    Daudin, Hist. Nat. Particuliere Reptiles, 8:53, 1803. Günther,
    Catalogue Batrachia Salientia Brit. Mus., p. 110, 1859. Boulenger,
    Catalogue Batrachia Salientia s. Ecaudata, p. 403, February 1,
    1882. Dunn, Occas. Papers, Boston Soc. Nat. Hist., 5:413, October
    10, 1931.

    _Hyla elaeochroa_ (part): Dunn and Emlen, Proc. Acad. Nat. Sci.
    Philadelphia, 84:25, March 22, 1932.

_Diagnosis._--Size medium; skull longer than wide; frontoparietal
fontanelle absent in adults; snout subovoid; choanae rounded; dorsal
stripes present; black vermiculations on posterior surfaces of thighs.

_Description._--Head flat, longer than wide; snout long, subovoid,
slightly protruding beyond lower lip; loreal oblique, concave; canthus
rounded, indistinct; diameter of eye about equal to interorbital
space; tympanum large, about three fifths diameter of eye, smaller
than internarial distance; supratympanic fold indistinct; arms short;
fingers free of webs; subarticular tubercles distinct; median palmar
tubercle large, bifid; inner palmar tubercle on base of first finger
flat, elongate; disc of third finger about one half diameter of
tympanum; legs moderately long; tarsal fold absent; inner metatarsal
tubercle distinct, oval; toes about half webbed; web on fourth toe
extending to disc; discs of toes about size of those on fingers; skin
smooth above with small granules on head and in scapular region in
some specimens; skin on flanks, throat, belly, and lower surfaces of
thighs granular; tongue oval, longer than wide, not free behind;
choanae small, oval; vocal slits long, lateral to tongue.

In preservative, dorsum pale brown with darker dorsolateral stripes;
narrow dark brown line from nostril to eye; groin, anterior surface of
thighs, and posteroventral surfaces of shanks creamy tan with dark
brown vermiculations; white spots present on thighs in some specimens;
throat flecked with brown; belly creamy white or gray.

_Remarks._--The taxonomic history of _Hyla rubra_ Laurenti is
confused. Seba (1734:70) illustrated and diagnosed a frog for which
he used the name _Ranula, Americana, Rubra_. Linnaeus (1758:213)
considered Seba's frog to be a variety of _Hyla arborea_. Laurenti
(1768:35) apparently examined the same individual that Seba called
_Ranula, Americana, Rubra_. For this specimen, Laurenti used the
binominal _Hyla rubra_ and provided a brief diagnosis. The type
locality was given as America.

Daudin (1802:26) redescribed the same specimen(s?) treated by Seba and
Laurenti and provided a fairly good description and figures. Daudin
restricted the type locality to Surinam and indicated that Marin de
Baize was the probable collector. Daudin (1802:26 and 1803:53)
neglected to consider Laurenti's work, but he applied the same name
used by Laurenti. Most authors have credited _Hyla rubra_ to Daudin,
but Rivero (1961:120) noted that _Hyla rubra_ Laurenti, 1768, has
priority over _Hyla rubra_ Daudin, 1802. Since both Laurenti and
Daudin worked on Seba's material, it is reasonable to assume that
Daudin redescribed the same frog that was named by Laurenti; this was
not an uncommon practice in the early nineteenth century. Thus I
conclude that _Hyla rubra_ Daudin, 1802, is a junior synonym of _Hyla
rubra_ Laurenti, 1768.

Dunn (1931a:413) first reported _Hyla rubra_ from Central America; he
recorded the species from the Canal Zone and San Pablo, Panamá. I have
examined the material of _Hyla rubra_ from Panamá deposited in various
museums. Most of the specimens are faded, discolored, and do not have
distinct brown vermiculations on the thighs. The specimens seem to be
more like _Hyla rubra_ than any of the other species in the _rubra_
group. The presence of oval choanae and a tympanum larger than the
largest finger disc separate these specimens from _Hyla elaeochroa_, a
species with which _rubra_ has been confused. _Hyla elaeochroa_ does
not occur in the Canal Zone or eastern Panamá. All museum specimens
from Nicaragua, Costa Rica, and western Panamá that have been called
_Hyla rubra_, plus those mentioned by Dunn and Emlen (1932:25) and
Dunn (1933:61) are _Hyla elaeochroa_.

The taxonomic status of the many South American populations referred
to _Hyla rubra_ and of other populations now recognized as different
species is not clear at the present time. Considerable variation in
external characters and in cranial features has been observed in South
American _rubra_. A review of the taxonomy of these populations is
beyond the scope of this paper. Possibly the Central American
specimens herein referred to _rubra_ will ultimately be found to be
specifically distinct from those in Surinam. Since I have no
osteological material from Central America, I have been unable to
describe the cranium in this account. Furthermore, I have no data on
the ecology and life history of _rubra_ in Central America.

_Distribution._--_Hyla rubra_ inhabits lowland tropical forests from
central-eastern Panamá to northern South America and thence through
lowlands east of the Andes to northern Argentina (Fig. 6).

_Specimens Examined._--Panamá: _Canal Zone_: Gatun, UMMZ 52720 (2);
Madden Dam, FMNH 67820; no specific locality, UMMZ 56517 (3), USNM
37863. _Colón_: Cerro Bruja, MCZ 13248. _Darién_: El Real, USNM
140569-70, 140573. _Panamá_: Juan Díaz, MCZ 17973; Las Sabanas, MCZ
17581; Río Trinidad, UMMZ 64003; San Pablo, MCZ 1398-9.


_Hyla elaeochroa_ Cope

    _Hyla elaeochroa_ Cope, Jour. Acad. Nat. Sci. Philadelphia, 8:105,
    1876 [Holotype.--USNM 30689, Sipurio, Limón Province, Costa Rica;
    William M. Gabb collector]. Günther, Biologia Centrali-Americana,
    Reptilia and Batrachia, p. 265, June 1901. Taylor, Univ. Kansas
    Sci. Bull., 35:859, July 1, 1952. Duellman, Univ. Kansas Publ.,
    Mus. Nat. Hist., 17:270, June 17, 1966.

    _Hyla quinquevittata_ Cope, Proc. Amer. Philos. Soc., 23:273,
    April 1887 [Holotype.--USNM 14187, Nicaragua; J. F. Bransford
    collector]. Günther, Biologia Centrali-Americana, Reptilia and
    Batrachia, p. 268, June 1901. Noble, Bull. Amer. Mus. Nat. Hist.,
    38:340, June 1918.

    _Hyla rubra_ (part): Dunn and Emlen, Proc. Acad. Nat. Sci.
    Philadelphia, 84:25, March 22, 1932.

    _Hyla dulcensis_ Taylor, Univ. Kansas Sci. Bull., 39:37, November
    18, 1958 [Holotype.--KU 32168, Golfito, Puntarenas Province, Costa
    Rica; Edward H. Taylor collector].

_Diagnosis._--Size medium (Male to 38 mm., Female to 40 mm.); skull
wider than long; nasals truncate anteriorly; frontoparietal fontanelle
moderate in size; snout slightly protruding; tympanum about size of
largest discs on fingers; dorsum marked by longitudinal stripes; dark
stripe between eye and nostril; in life tan to olive-green with or
without dark mark between eyes; bones greenish blue.

_Description._--Head flat, longer than wide; snout long, rounded,
protruding beyond mouth; canthus indistinct; length of eye equal to
interorbital distance; loreal region not pronounced; tympanum distinct
and about two-fifths diameter of eye; interorbital triangle present or
absent; arms short; trace of web between fingers, extending as fringe
along sides of fingers; first finger very short with small disc; other
discs about size of those on toes; discs on third finger and fourth
toe as large as tympanum; outer palmar tubercle moderate in size,
partly bifid; inner palmar tubercle large, elongate, flat;
subarticular tubercles distinct; legs moderately long; tarsal fold
absent; inner metatarsal tubercle flat; outer metatarsal tubercle
smaller, indistinct; subarticular tubercles moderate in size; fringe
on toes to tip of disc of second toe; rest of toes about two-thirds
webbed; foot length about two fifths snout-vent length; tibia length
about one half snout-vent length; skin above smooth or with minute
pustules; belly finely granular; ventral surfaces of thighs and areas
below anus granular; skin on ventral surfaces of limbs smooth; tongue
relatively large, longer than wide, barely notched behind; vocal slits
elongate, lateral to tongue; choanae medium in size. In life, dorsum
yellowish brown, olive green, or grayish brown with dark brown spots
on snout, dark brown stripe from nostril to eye, dark yellow-brown
interorbital triangle, and dark supratympanic region; generally five
interrupted longitudinal dark brown stripes on dorsum (one on each
flank, pair of paravertebral and one vertebral); flanks pale yellow;
groin yellowish brown; thighs marked with one or two transverse
yellow-brown blotches; shanks with two or three yellow-brown blotches
above; spaces between blotches on thighs, shanks, tarsi, and feet
yellow; brown spots on tarsi and in some specimens on feet; arm pale
yellow with pale brown spots; belly creamy white having slight
blue-green tint; vocal sac and chin yellow; axillary region yellow,
blue-green in some specimens (Pl. 2A).

In preservative, head and dorsum yellowish brown; dark brown stripe
from nostril to eye; dark brown spots on snout; a dark brown
interorbital triangle with apex directed backward; dark brown
supratympanic region; dorsal stripes same as in living individuals;
flanks pale yellow with brown spots in some specimens; groin creamy
white; thighs and shanks having or lacking transverse dark brown
blotches; spaces between blotches creamy white or yellow-brown; arms
pale yellowish brown; belly and vocal sac creamy white.

_Variation._--Geographic variation in size and some proportions, such
as the ratio of tibia length to snout-vent length and the ratio of the
diameter of the tympanum to that of the eye, have been observed in
this species. The largest individuals are from the Golfo Dulce region
(samples from Piedras Blancas and Rincón de Osa), Puntarenas Province,
Costa Rica. The smallest individuals are from El Recreo, Zelaya
Province, Nicaragua, and from the Caribbean lowlands of Costa Rica.

The diameter of the tympanum is proportionately larger (relative to
the size of the eye) in males from Tilarán, Guanacaste Province; the
tympanum is nearly as large in males from Piedras Blancas, Puntarenas
Province, and Puerto Viejo, Heredia Province, Costa Rica. The lowest
ratios occur in individuals from Almirante, Bocas del Toro, Panamá, in
specimens from the Caribbean lowlands of Costa Rica (except Puerto
Viejo), and in those from El Recreo, Zelaya Province, Nicaragua. In
general, the tympanum is proportionately larger in females than in
males; the tympanum is largest in females from the Pacific lowlands
of Costa Rica (Table 5).

Color variation has been observed in individuals from the same
population, as well as in individuals from different localities,
between males and females, and from night to day. In life, most
individuals from the Pacific lowlands of Costa Rica are dark tan to
greenish gray above with dark brown longitudinal stripes that are
entire or broken, but some specimens (mostly males) are dusky brown
and lack longitudinal stripes or an interorbital triangle; females
usually have the dark interorbital triangle and the stripes on the
dorsum. Individuals from Turrialba, Cartago Province, Costa Rica, are
pale olive-tan with olive-brown markings. Individuals from Puerto
Viejo, Heredia Province, Costa Rica, are uniformly yellowish brown
with or without dark longitudinal stripes. Specimens from El Recreo,
Zelaya Province, Nicaragua, are like those from Puerto Viejo. Males
from Almirante, Bocas del Toro, Panamá, are pale brown with dark brown
longitudinal stripes and an indistinct interorbital triangle. Females
have a distinct interorbital triangle and dark brown blotches on the
thighs and shanks.

By night, the dorsum usually is pale yellow, and the belly is creamy
white. By day, the dorsum is dark tan; the stripes and spots are
darker, and the belly is yellowish white. Taylor (1952) noticed that
considerable variation in color pattern occurred from night to day in
individuals from Turrialba, Cartago Province, Costa Rica. At night
some individuals lacked a dorsal pattern, but by day many of these
individuals developed dorsal stripes.

_Cranial Osteology._--The skull of _Hyla elaeochroa_ is slightly wider
than it is long, and flat. The premaxillary is small and bears 10 to
15 teeth (mean for 9 specimens, 12.3). The alary process of the
premaxillary is small, vertical, and slightly concave posteriorly.
Ventrally, the premaxillary is partially united to the prevomer by
ossification. The maxillary is slender and bears 70 to 82 teeth (mean
for 9 specimens, 74.3). The pars facialis of the maxillary is
laterally convex and is about twice as high as the pars dentalis.

The nasal is large, robust, anteriorly truncate, but pointed
posteriorly in dorsal view. The nasal comprises about 45 per cent of
the total length of the skull. There is an anterior cartilaginous
septum nasi separating the two nasals; the latter overlap the
sphenethmoid posteriorly. Each nasal bears a shallow concavity in the
midlateral side and lacks a maxillary process. Dorsally, the
sphenethmoid is wider than long, roughly pentagonal in shape; the
frontoparietal is elongate, smooth, and bears a small anterior
supraorbital process. The sphenethmoid and frontoparietal form the
anterior margin of the frontoparietal fontanelle; the fontanelle is
narrow anteriorly and wider posteriorly (Fig. 5B).

The entire distal surface of the proötic is in contact with the
posterior arm of the squamosal. A narrow cartilaginous crista parotica
is visible dorsally in some specimens. The squamosal is broad
posteriorly but its anterior arm is slender and not in contact with
the maxillary.

TABLE 5.--Geographic Variation in Size and Proportions in Males of
_Hyla elaeochroa_. (Means in parentheses below observed ranges.)

==========================================================================
                     |    |Snout-vent|   Tibia    |         |
                     |    | length   |   length/  |Tympanum/|Foot length/
Locality             |  N |  (mm.)   | snout-vent |   eye   | snout-vent
---------------------+----+----------+------------+---------+-------------
Nicaragua: El Recreo |  9 | 28.0-30.3|  0.51-0.57 |0.47-0.59| 0.39-0.54
                     |    |  (29.3)  |   (0.55)   | (0.51)  |  (0.41)
                     |    |          |            |         |
Costa Rica: Tilarán  | 21 | 28.8-33.6|  0.47-0.57 |0.48-0.65| 0.40-0.46
                     |    |  (30.6)  |   (0.52)   | (0.59)  |  (0.41)
                     |    |          |            |         |
Costa Rica: Puerto   | 22 | 26.3-32.4|  0.49-0.54 |0.48-0.65| 0.38-0.45
  Viejo              |    |  (29.7)  |   (0.52)   | (0.57)  |  (0.42)
                     |    |          |            |         |
Costa Rica: Turrialba| 95 | 28.1-35.0|  0.47-0.56 |0.47-0.68| 0.37-0.46
                     |    |  (30.6)  |   (0.51)   | (0.56)  |  (0.41)
                     |    |          |            |         |
Costa Rica: Bataán,  | 26 | 26.3-32.7|  0.47-0.54 |0.45-0.66| 0.36-0.44
  Limón, and Suretka |    |  (30.0)  |   (0.51)   | (0.50)  |  (0.41)
                     |    |          |            |         |
Costa Rica: Piedras  | 21 | 33.3-37.7|  0.50-0.54 |0.48-0.64| 0.40-0.46
  Blancas            |    |  (35.2)  |   (0.51)   | (0.57)  |  (0.43)
                     |    |          |            |         |
Costa Rica: Rincón de| 24 | 31.4-35.9|  0.50-0.56 |0.45-0.61| 0.40-0.46
  Osa                |    |  (34.1)  |   (0.53)   | (0.54)  |  (0.43)
                     |    |          |            |         |
Panamá: Bocas del    |  6 | 31.0-33.5|  0.49-0.54 |0.47-0.50| 0.41-0.43
  Toro               |    |  (32.1)  |   (0.51)   | (0.48)  |  (0.42)


  [Illustration: PLATE 1

  Living _Hyla_: (A) _H. boulengeri_ (KU 86322) and (B) _H.
  foliamorta_ (KU 101576), × 2.]

  [Illustration: PLATE 2

  Living _Hyla:_ (A) _H. elaeochroa_ (KU 91688), (B) _H. staufferi
  staufferi_ (KU 57791), and (C) _H. staufferi altae_ (KU 101688), ×
  2.]

  [Illustration: PLATE 3

  Audiospectrograms and sections of mating calls of (A) _Hyla
  boulengeri_ (KU Tape No. 511) and (B) _H. foliamorta_ (KU Tape No.
  511) and (B) _H. foliamorta_ (KU Tape No. 288).]

  [Illustration: PLATE 4

  Audiospectrograms and sections of mating calls of (A) _Hyla
  elaeochroa_ (KU Tape No. 97), (B) _H. s. staufferi_ (KU Tape No.
  93), and (C) _H. staufferi altae_ (KU Tape No. 502).]

The prevomer is short, and broadest anteriorly. The prevomer is joined
to the premaxillary by ossification. The posterior margin of the
prevomer bears a narrow cartilaginous articulation with the
sphenethmoid. The anterolateral and posterolateral processes of the
prevomer form an incomplete bony margin to the small choanae; each
prevomer bears four to seven teeth. The palatine is small, curved
anteriorly and edentate. The anterior part of the parasphenoid is
robust and ends in a point. The pterygoid is slender and weakly
developed.

_Natural History._--_Hyla elaeochroa_ inhabits humid lowland tropical
forests in lower Central America and breeds in temporary ponds.
Clasping pairs, gravid females, and calling males have been found
mostly in June, July, and August. William E. Duellman informed me that
he also found males calling in mid-February, late April, and May.
Duellman (1967) reported detailed observations of the social
organization in the mating call of _Hyla elaeochroa_. The choruses in
this species are initially organized, but when many individuals call,
the chorus loses organization. I observed this species breeding in a
temporary pond at Puerto Viejo, Heredia Province, Cost Rica, in late
June. Calling males and clasping pairs were extremely abundant within a
few hours after a heavy rain. Males were mostly found calling from low
emergent herbs in the pond and less commonly from bushes and trees to
heights of six meters above the water. Calling males were also observed
at Ricón de Osa, Puntarenas Province, Costa Rica, in late July. These
breeding individuals were found in a shallow pond at the edge of a wet
forest. Calling stations were less than two meters in height. John D.
Lynch informed me that after a heavy rain in early August, he found
several hundred individuals congregated in a small grassy pond less
than a foot deep, at Rincón de Osa. Males were calling from sites on
grass stems a few centimeters above the water.

The mating call of _Hyla elaeochroa_ consists of short notes, repeated
at intervals of about 0.40 second. Each note has a duration of 0.12 to
0.24 second. The fundamental frequency varies from 48 to 65 cycles per
second, and the notes have 40-50 pulses per second; the dominant
frequency is at about 2,900 cycles per second (Table 2, Pl. 4A).

The eggs are deposited in a mass in the water near floating vegetation.
William E. Duellman informed me that he observed hatchlings oriented
vertically with the tip of the mouth at the surface of the water. They
gradually sank to bottom, but swam back to surface again. No additional
information is available concerning early development. Tadpoles have
been found in shallow grassy ponds in clearings and in temporary
woodland ponds.

_Tadpoles._--Three hundred and thirty-one tadpoles in various stages of
development are available. Thirty-five tadpoles in stage 35 have a mean
body length of 8.1 mm. (8.0-9.0 mm.), tail length of 17.7 mm.
(15.0-19.5 mm.), and total length of 25.9 mm. (23.0-27.5 mm.). The
largest tadpole examined is in stage 40 and has a total length of 34.5
mm. (Table 6).

A typical tadpole, stage 35 of development (KU 104134, from Puerto
Viejo, Heredia Province, Costa Rica), has a body length of 9.1 mm.,
tail length of 17.7 mm., and a total length of 26.8 mm. Other
characters are as follows: body depressed anteriorly; body length
greater than depth of tail; internarial space as broad as interorbital
distance; nostril equidistant between eye and tip of snout; eyes
moderately large; mouth anteroventral and triangular; median fourth of
upper lip bare; rest of lip bordered by one row of papillae; clumps of
small papillae at corners of mouth; tooth rows 2/3; upper rows equal in
length; second row interrupted medially; lower rows shorter than upper
rows, diminishing in length; beak rather weak with small serrations;
spiracle short and nearer eyes than anus; anal opening not reaching
edge of ventral fin; caudal musculature attenuated distally (Figs. 2B
and 3B).

TABLE 6.--Sizes of Tadpoles of _Hyla elaeochroa_ in Relation to
Developmental Stages. (Means in parentheses below observed ranges;
measurements in mm.)

    ------+---+-------------+-------------+--------------
    Stage | N | Body length | Tail length | Total length
    ------+---+-------------+-------------+--------------
      24  | 2 |  4.0-4.0    |  8.5-9.0    |  12.5-13.0
          |   |   (4.0)     |   (8.8)     |   (12.8)
          |   |             |             |
      25  |64 |  5.0-6.5    |  8.5-15.0   |  13.5-21.5
          |   |   (5.7)     |   (11.8)    |   (17.6)
          |   |             |             |
      27  |30 |  7.0-7.5    | 13.0-16.0   |  20.0-23.0
          |   |   (7.1)     |   (14.2)    |   (21.3)
          |   |             |             |
      30  |15 |  7.0-8.0    | 13.0-16.5   |  20.0-24.0
          |   |   (7.3)     |   (15.0)    |   (22.4)
          |   |             |             |
      32  |30 |  7.5-8.5    | 15.0-17.0   |  22.5-25.0
          |   |   (7.8)     |   (16.1)    |   (23.8)
          |   |             |             |
      35  |35 |  8.0-9.0    | 15.0-19.5   |  23.0-27.5
          |   |   (8.1)     |   (17.7)    |   (25.9)
          |   |             |             |
      37  |22 |  8.5-9.5    | 16.0-22.0   |  25.0-31.0
          |   |   (9.0)     |   (18.8)    |   (27.8)
          |   |             |             |
      39  |14 |  9.5-10.5   | 19.0-24.9   |  28.5-33.5
          |   |   (9.9)     |   (21.1)    |   (31.0)
          |   |             |             |
      40  |27 |  7.0-11.5   | 15.0-23.0   |  23.0-34.5
          |   |   (9.1)     |   (22.0)    |  (31.2)
          |   |             |             |
      43  |10 |  8.0-12.0   | 11.0-17.0   | 20.0-26.0
          |   |  (10.2)     |   (13.5)    |  (23.7)
          |   |             |             |
      45  |16 | 10.0-12.0   |  1.0-7.0    | 12.0-17.0
          |   |  (11.2)     |   (3.4)     |  (14.6)
          |   |             |             |
      46  |45 | 11.0-13.0   |             |
          |   |  (11.8)     |             |

In life, dorsum yellowish tan with gray-brown mottling; belly and
ventrolateral surfaces silvery-gold or white; black stripe from tip of
snout to eye; two black blotches below eye, another blotch extending
from eye to base of caudal musculature; caudal musculature and fins
gray-brown. In preservative, yellowish tan and silvery-gold colors
lost; black reticulations present on tail.

_Remarks._--Cope (1876:105) described _Hyla elaeochroa_ from Sipurio,
Limón Province, Costa Rica. He based his description on a small
specimen, 26.0 mm. in snout-vent length, having a dorsum uniformly
colored and lacking an interorbital triangle and blotches on the
thighs. Cope (1887) described pigmented specimens from Nicaragua as
_Hyla quinquevittata_, which he diagnosed as having dark brown bars on
the hind limbs and five dark brown longitudinal stripes on the dorsum,
the median one of which was expanded anteriorly so as to form a large
triangular spot between the eyes. He thought this species was related
to _Hyla eximia_ Baird and noted that "the hinder legs are much larger;
the muzzle is more acuminate and the color bands are much wider" than
in _eximia_. Cope did not compare _quinquevittata_ with _elaeochroa_,
which he had described ten years before. Günther (1901:268), Noble
(1918:340), and Nieden (1923:251) regarded both _elaeochroa_ and
_quinquevittata_ as valid species. Dunn and Emlen (1932:25) regarded
both as synonyms of _Hyla rubra_, but they made no qualifying
statements. Taylor (1952:859) placed _quinquevittata_ as a synonym of
_elaeochroa_ and indicated that _rubra_ was another species.

Taylor (1958:37) described _Hyla dulcensis_ from the humid tropical
forests of Golfo Dulce, Puntarenas Province, Costa Rica. He thought
this species was "related to _H. elaeochroa_ but differs in its
somewhat larger size, smaller finger and toe discs, the obsolete
canthus rostralis; the loreal region concave and the choanae larger."
Duellman (1966a:270) compared adults, tadpoles, and mating calls of
_dulcensis_ and _elaeochroa_ and concluded that a single species was
involved.

_Hyla elaeochroa_ can be easily confused with the closely related _Hyla
staufferi_. Although the durations of the calls are similar, the call
of _elaeochroa_ has only about one third the number of pulses per
second, a much lower fundamental frequency, and a lower dominant
frequency than that of _staufferi_. _Hyla elaeochroa_ is larger and has
a less pointed snout than does _staufferi_. Although the skulls of the
two species are similar, that of _elaeochroa_ differs in having broad
palatines and comparatively larger nasals that are truncate anteriorly.
In _staufferi_ the nasal is rounded anteriorly and the palatine is
absent.

_Distribution._--_Hyla elaeochroa_ occurs on the Caribbean lowlands
from western Panamá through Costa Rica to eastern Nicaragua, and on the
Pacific lowlands of southeastern Costa Rica and extreme western Panamá.
Most localities where it has been collected are below 800 meters, but
the species has been found at two localities above 1000 meters (El
Silencio and Pacuare, Cartago Province) on the Caribbean slopes of the
Cordillera de Talamanca, Costa Rica (Fig. 6).

_Specimens Examined._--Nicaragua: _Zelaya_: El Recreo, UMMZ 79721 (9).

Costa Rica: _Alajuela_: Laguna Monte Alegre, KU 64499. _Cartago_: 2 km E
Chitaría, KU 107058; El Silencio, 14.4 km NE Turrialba, KU 107059-60;
4.6 km ENE Pacuare, KU 64451-75, 64628-37; 4 km S Pavones, KU 64500;
Turrialba (Instituto Interamericano de Ciéncias Agrícolas), KU 30305-26,
24616-57, 30337-54, 31776-91, 31803, 31807-15, 64413-50, 68283-87
(skeletons), 68390-1 (young), 35042 (eggs), 25207-8 (skeletons), 25221
(skeleton), 41073-83 (skeletons). _Guanacaste_: 2 km E Tilarán, KU
86356-77, 87667-8 (young). _Heredia_: Puerto Viejo, KU 36696, 46466,
64501-17, 68288-91, 68387, 68388-9 (young), 91803 (young), 91688-9,
104134 (tadpoles), 104135 (young), 104354-6 (skeletons); 1.5 km N Puerto
Viejo, KU 64518-23, 68386 (tadpoles); 1 km S Puerto Viejo, KU 84985-6
(skeletons), 87669 (young), 87772-3 (skeletons). _Limón_: Bataán, KU
30327-36; La Lola, KU 64478-98, 68281-2 (skeletons); Los Diamantes, KU
31800-02, 64476-7; Peralta, KU 31816-21; Puerto Limón, KU 31792-99;
Suretka, KU 36467-79, 36697, 41084. _Puntarenas_: 5 km NW Buenos Aires,
KU 107057; 10 km E Esparta, KU 87666 (tadpoles); Golfito, KU 32166-8; 8
km E Palmer Norte KU 93939; 10.7 km SE Palmar Sur, KU 93938 (skeleton),
93940-51, 93952 (eggs), 93953-6 (tadpoles); Piedras Blancas, KU
103646-59; 4.5 km W Rincón de Osa, KU 102208-41, 104298 (tadpoles).

  [Illustration: Fig. 6. Map showing locality records for _Hyla
  elaeochroa_ (circles) and _H. rubra_ (dots).]

Panamá: _Bocas del Toro_: Almirante, KU 80079; Isla Bastimentos, KU
96008-11; Río Cricamola, 3.7 km from coast, KU 96012. _Chiriquí_: Río
Gariché, 8.3 km ESE Paso de Canoas, KU 101571-2.


_Hyla staufferi_ Cope

    _Hyla staufferi_ Cope, Proc. Acad. Nat. Sci. Philadelphia, 17:165,
    October 1, 1865 [Holotype.--USNM 15317, Orizaba, Veracruz, México;
    Francis Sumichrast collector].

_Diagnosis._--Small frogs (Male to 29 mm., Female to 31.6 mm.); skull
longer than wide; palatine absent; large cartilaginous crista parotica
present; snout flat, elongate and protruding; dark interorbital bar and
dorsal stripes usually present.

_Description._--Head flat, especially in females, longer than wide;
snout long, protruding beyond mouth; loreal region concave; canthus
ill-defined; length of eye greater than internarial distance or width
of eyelid; length of eye less than interorbital space; tympanum
distinct; interorbital spot irregular; supratympanic fold faint; arms
short; fingers free of webs; discs on third and fourth fingers equal to
diameter of tympanum; inner metatarsal tubercle on base of first finger
distinct; first finger shorter than second; palmar tubercle distinct
(Fig. 1C); legs short (usually less than 50 per cent of snout-vent
length); tarsal fold absent; metatarsal tubercles small, outer tubercle
smaller than inner; subarticular tubercles small, simple, distinct;
toes less than half webbed (Fig. 1D); skin smooth above with a few
small pustules on head, scapular region, flanks, and supratympanic
region; arms and legs smooth; skin of belly coarsely granular;
posteroventral surfaces of thighs finely granular; tongue small,
rounded, longer than wide, slightly free and notched posteriorly; vocal
slits small, lateral to tongue; choanae moderate in size.

_Variation._--The largest males of _Hyla staufferi_ are from Jalapa,
Guatemala, and from San Salvador, El Salvador. In these samples the
average snout-vent length is 27 mm. In Panamanian specimens the average
snout-vent length is 23.6 mm. Slight variation in the ratio of tibia
length to snout-vent length exists throughout the range; more variation
exists in the ratio of the diameter of the tympanum to that of the eye;
the tympanum is proportionately larger in northern populations (Table
7). The primary differences between Panamanian and more northern
populations are in size, color pattern on the dorsum and shanks, amount
of webbing between the toes, and duration of notes in the mating call
(Table 2, Pl. 4).

The color in Panamanian _staufferi_ is gray or gray-brown with a pair
of distinct, complete, dark brown dorsolateral stripes, a pair of
entire paravertebral stripes, and in some specimens a vertebral stripe.
About five per cent of the individuals have interrupted stripes on the
dorsum, whereas in the more northern populations complete paravertebral
stripes are present in less ten per cent of the specimens; when
complete stripes are present, they are irregular. The dorsal ground
color in non-Panamanian specimens is brown, olive-brown, or dark brown.

Transverse bars are present on the shanks in _Hyla staufferi_ from
Costa Rica northward to México, whereas in Panamá all the individuals
have a longitudinal stripe on the shank (Table 7, Pl. 2). The
interorbital spot or bar is more noticeable in northern populations
than in specimens from Panamá. Frogs from Costa Rica and northward have
the toes about three fourths webbed, whereas in Panamá the toes are
about two fifths webbed. The mating calls of the northern and
Panamanian populations are similar, but the notes have a longer
duration in the northern populations and a higher dominant frequency in
Panamanian populations.

_Hyla staufferi_ is the most variable member of the _Hyla rubra_ group
in Central America. The Panamanian populations are geographically
separated from the Costa Rican and more northern populations by an area
of tropical rainforest in the Golfo Dulce region in southeastern Costa
Rica and adjacent Panamá. _Hyla staufferi_ does not occur on the
Caribbean versant of Costa Rica and Panamá. The Golfo Dulce region and
the Caribbean versant are humid and inhabited by _Hyla elaeochroa_.
_Hyla staufferi_ is an inhabitant of subhumid and xeric areas.

On the basis of the discontinuous variation in several characters which
correlate with the disjunct distribution of the two populations, two
subspecies of _Hyla staufferi_ are recognized. The accounts that follow
apply equally to each.

_Cranial Osteology._--The skull of _Hyla staufferi_ is flat and longer
than wide. The premaxillary is small and bears 9 to 13 teeth (mean for
5 specimens, 11.3). The alary process of the premaxillary is small,
concave posteriorly and vertical. Ventrally, the premaxillary is united
to the prevomers by partially ossified cartilage. The maxillary is
slender and usually bears 49 to 70 teeth (mean for 5 specimens, 60.7).
The pars facialis of the maxillary is convex and less than twice the
height of the pars dentalis.

The nasal is large, rounded anteriorly, and pointed posteriorly in
dorsal view. The nasal comprises about 40 per cent of the total length
of the skull. Anteromedially the two nasals converge; posteriorly they
overlap the sphenethmoid. The nasals lack a concavity in the midlateral
surface. Dorsally, the sphenethmoid is wider than long, roughly
pentagonal in shape; the frontoparietal is elongate, narrow, and
smooth, with a small supraorbital process anteriorly. The
frontoparietal fontanelle is narrow anteriorly and wide posteriorly.

TABLE 7.--Geographic Variation in Size and Color in Males of _Hyla
staufferi_. (Means in parentheses below observed ranges.)

    =================================================================
                   |     |            |Complete dorsal|
                   |     |Snout-vent  |    stripes    |Barred shanks
    Locality       |  N  |length (mm.)|  (per cent)   |  (per cent)
    ---------------+-----+------------+---------------+--------------
    Veracruz       |  47 |  23.0-27.3 |      0.0      |     100
                   |     |   (25.4)   |               |
                   |     |            |               |
    Campeche       |  20 |  24.6-27.5 |      0.0      |     100
                   |     |   (25.5)   |               |
                   |     |            |               |
    Oaxaca         |  75 |  24.0-28.7 |      9.3      |     100
                   |     |   (26.4)   |               |
                   |     |            |               |
    Chiapas        |  20 |  23.2-27.8 |     10.0      |     100
                   |     |   (25.5)   |               |
                   |     |            |               |
    Guatemala      |  22 |  25.0-29.0 |     10.9      |     100
                   |     |   (26.9)   |               |
                   |     |            |               |
    El Salvador    |  21 |  24.7-28.6 |      0.0      |     100
                   |     |   (27.0)   |               |
                   |     |            |               |
    Honduras       |  34 |  20.6-27.0 |      3.3      |     100
                   |     |   (24.9)   |               |
                   |     |            |               |
    Nicaragua      |  67 |  21.5-26.8 |      3.0      |      92.7
                   |     |   (24.9)   |               |
                   |     |            |               |
    Costa Rica     |  54 |  20.7-26.6 |      5.5      |      98.1
                   |     |   (24.2)   |               |
                   |     |            |               |
    Total          | 360 |  20.7-29.0 |      5.4      |      98.3
    Non-Panamanian |     |   (25.9)   |               |
                   |     |            |               |
    Panamá         |  72 |  21.7-26.0 |     94.5      |       0.0
                   |     |   (23.6)   |               |

Only a narrow connection exists between the posterior, pointed arm of
the squamosal and the lateral edge of the proötic. The crista parotica
is visible dorsally along the lateral edge of the bony proötic. The
squamosal is narrow anteriorly and posteriorly.

The prevomers are short and separated anteriorly by partly ossified
cartilage of the overlying solum nasi. The prevomer is joined to the
premaxillary by cartilage. The posterior margin of the prevomer
articulates directly with the sphenethmoid. The anterolateral and
posterolateral processes of the prevomers form the incomplete bony
internal margin of the choanae. Each prevomer bears three to six teeth.
The palatine is absent. The anterior part of the parasphenoid is narrow
and ends in a point. The pterygoid is slender and weakly developed.

_Natural History._--Throughout its range _Hyla staufferi_ occurs in
subhumid forests and savannas; consequently, the breeding activities
are limited by the seasonal occurrence of rainfall, which accumulates
in temporary ponds where this species breeds. Clasping pairs and gravid
females have been found mostly from June to August throughout its
range. This species was observed calling at Finca Taboga, Guanacaste
Province, Costa Rica, in mid-July. The males were calling from
temporary grassy and weedy ponds in which _Hyla microcephala_ also was
calling, but the two species had different calling sites. _Hyla
staufferi_ called at stations at heights of five to 80 cm. near the
edge of the pond, whereas _Hyla microcephala_ called from emergent
vegetation in the middle of the pond. Charles W. Myers informed me that
at Penonomé, Coclé, Panamá, he found _staufferi_ calling from grass in
puddles where _microcephala_ was absent, and at El Caño, Coclé, Panamá,
_staufferi_ was calling from higher sites ("several inches to a few
feet above water") than _microcephala_.

Stuart (1948:34) reported breeding individuals from La Libertad,
Guatemala, after rainfall in late May, and Schmidt and Stuart
(1941:239) reported _staufferi_ breeding in July in the Salamá basin,
Alta Verapaz, Guatemala. Stuart (1935:38) and Duellman (1960:63 and
1963:226) agreed that this species breeds early in the rainy season.
However, Rand (1957:519) stated that in El Salvador "these frogs did
not begin to call until almost a month and a half after the beginning
of the rains." Blair (1960:133) reported that males call in June and
July in Chiapas, Oaxaca, Veracruz, and Tamaulipas, México.

The mating call of this species is a series of closely spaced notes
having a fundamental frequency of about 100 cycles per second. Each
note has a duration of 0.13 to 0.23 second, repeated at intervals that
are longer than the duration of the call. The notes are moderately
low-pitched and have a dominant frequency of more than 3,000 cycles per
second and about 120 pulses per second (Table 2).

_Tadpoles._--Measurements of the 33 tadpoles that are available are
given in Table 8. The largest tadpole examined is in stage 38 and has a
total length of 29.5 mm.

A typical tadpole in stage 38 of development (KU 104162, 5 km ESE
Córdoba, Veracruz, México) has a body length of 10 mm., tail length of
19.5 mm., and a total length of 29.5 mm. Other characters are as
follows: body as deep as wide, depressed anteriorly; body as long as
depth of tail; interorbital space greater than distance between eye and
snout but equal to internarial space; nostril equidistant between eye
and tip of snout; distance between spiracle and eye less than distance
between eye and snout; eyes large, situated dorsolaterally; mouth
anteroventral, approximately triangular in outline; one row of papillae
covering lower lip and all except median fourth of upper lip; scattered
papillae at corners of mouth; tooth rows 2/3; first upper row entire,
second row interrupted medially, shorter than first; lower rows shorter
than upper rows; beak weak; spiracle short and nearer eyes than anus;
anal opening not reaching edge of ventral fin; dorsal fin barely
extending onto body; caudal musculature pointed distally.

TABLE 8.--Sizes of Tadpoles of _Hyla s. staufferi_ in Relation to
Developmental Stages. (Means in parentheses below observed ranges;
measurements in mm.)

    ======================================================
    Stage   | N | Body length| Tail length | Total length
    --------+---+------------+-------------+--------------
      25    | 3 |  6.0-7.0   |  12.0-13.0  |  18.0-20.0
            |   |   (6.7)    |   (12.5)    |   (19.2)
            |   |            |             |
      26    | 2 |  7.0-7.5   |  14.0-15.0  |  21.5-22.0
            |   |   (7.3)    |   (14.5)    |   (21.8)
            |   |            |             |
      27    | 9 |  7.0-8.0   |  13.0-17.0  |  21.0-25.0
            |   |   (7.6)    |   (14.5)    |   (22.0)
            |   |            |             |
      32    | 1 |   8.5      |    15.5     |    24.0
            |   |            |             |
      36    | 2 |   8.0-10.0 |  16.5-17.0  |  25.0-26.5
            |   |   (9.0)    |   (16.8)    |   (25.8)
            |   |            |             |
      38    | 6 |   9.0-10.0 |  19.0-20.5  |  28.0-29.5
            |   |   (9.6)    |   (19.5)    |   (29.1)
            |   |            |             |
      41    | 1 |  10.0      |    14.0     |    24.0
            |   |            |             |
      42    | 6 |  11.0-14.0 |  10.0-13.0  |  20.0-29.0
            |   |   (11.8)   |   (11.9)    |   (24.8)
            |   |            |             |
      45    | 1 |  12.5      |     0.5     |    13.0
            |   |            |             |
      46    | 1 |  13.0      |     --      |     --

In life, body pale olive-tan, belly silvery white with pinkish-orange
reticulations in some specimens; tail creamy white with silvery flecks
and black or brown reticulations. In preservative, tan and
pinkish-orange coloration lost; body transparent, reticulations on tail
present.

_Remarks._--_Hyla staufferi_ was described by Cope (1865:195) on the
basis of specimens from Orizaba, Veracruz, México. He described the
color pattern as "color above dark olive, with a short black bar over
each scapula, and one from eye to eye, with a trace along the coccyx."
Cope (1887:14) placed _staufferi_ as a subspecies of _Hyla eximia_, but
he did not justify his action. Günther (1901:262) also considered
_staufferi_ to be conspecific with _eximia_ without making any
qualifying statement. Dunn and Emlen (1932:24) named _Hyla culex_ from
Tela, Honduras, on the basis of a male (MCZ 16098) having a snout-vent
length of 25.1 mm., and a female (USNM 20267) from Patuca, Honduras.
They diagnosed the species as having "discs larger than tympanum ...
black interorbital triangle, traces of black dorsal marking; three
black bars on anterior and posterior face of thighs, two black bars on
tibia, on tarsus and on forearm." The holotype now is faded but has
some of the pattern described. Dunn and Emlen did not compare _culex_
with _staufferi_ but did compare it with _boulengeri_ and _rubra_.

Dunn (1933:61) named _Hyla altae_ from Summit, Canal Zone. His
description was based on a male (MCZ 17972) having a snout-vent length
of 25.1 mm., the color pattern was described as "gray with four darker
dorsal stripes ... a faint trace of mid-dorsal striping...." Dunn
defined the _Hyla rubra_ group and recognized _boulengeri_, _altae_,
_culex_, and _rubra_ as members. _Hyla elaeochroa_ and _staufferi_ were
omitted from his key to the group in Central America.

Kellogg (1932:174) compared _staufferi_ with _eximia_ and concluded
that the two were probably distinct species. Stuart (1935:38)
considered _altae_ to be a synonym of _culex_. Gaige (1936:293)
considered _altae_ and _culex_ to be conspecific but regarded
_staufferi_ as a different species. She also suggested that _staufferi_
was not related to _eximia_ but belonged to the _rubra_ group. Taylor
(1952:865) and Duellman (1966a:274) considered _altae_ and _culex_ to
be synonyms of _staufferi_.

The only other worker besides Cope and Günther to consider _Hyla
staufferi_ as a member of the _eximia_ group was Blair (1960:129), who
suggested the relationship on the basis of similarities in the
structure of the calls of _eximia_ and _staufferi_. Taylor (1938:421)
and Smith and Taylor (1948:78) excluded _staufferi_ from the _eximia_
group on the basis of morphological characteristics. I consider _culex_
to be inseparable from _staufferi_, whereas _altae_ is recognizable as
a Panamanian subspecies of _staufferi_.


_Hyla staufferi staufferi_ Cope, New Combination

    _Hyla staufferi_ Cope, Proc. Acad. Nat. Sci. Philadelphia, 17:195,
    October 1865 [Holotype.--USNM 15317, Orizaba, Veracruz, México;
    Francis Sumichrast collector], Brocchi, Mission Scientifique au
    Mexique et dans L'Amerique Centrale, 1881, p. 36. Boulenger,
    Catalogue, of the Bratrachia Salientia s. Ecaudata, p. 400,
    February 1, 1882. Kellogg, Bull. U.S. Natl. Mus., 160:173, March
    31, 1932. Smith and Taylor, Bull. U.S. Natl. Mus., 194:88, 1948.
    Taylor, Univ. Kansas Sci. Bull., 35:862, July 1, 1952. Rand,
    Fieldiana Zool. Chicago Nat. Hist. Mus., 34:518, April 18, 1957.
    Duellman, Univ. Kansas Publ, Mus. Nat. Hist., 17:274, June 17,
    1966.

    _Hyla eximia staufferi_ Cope, Bull. U.S. Natl. Mus., 32:14, January
    16, 1887.

    _Hyla eximia_ (part): Günther, Biologia Centrali-Americana,
    Reptilia and Batrachia, p. 261, June 1901. Nieden, Das Tierreich,
    Anura I, p. 245, June 1923.

    _Hyla culex_ Dunn and Emlen, Proc. Acad. Nat. Sci. Philadelphia,
    84:24, March 22, 1932 [Holotype.--MCZ 16098, Tela Honduras; Raymond
    A. Stadelman collector]. Stuart, Misc. Publ., Univ. Michigan Mus.
    Zool., 29:38, October 1935. Gaige, Carnegie Inst. Washington Publ.,
    457:293, 1936.

_Diagnosis._--Small frogs (Male to 29 mm., Female to 31.6 mm.);
dorsolateral stripes irregular; paravertebral stripes usually broken;
two or three transverse bars on shanks; thighs spotted or not; arms
usually barred; interorbital bar usually present; toes about three
fourths webbed; color brown, tan, or olive-green.

_Variation._--Three hundred and sixty males chosen at random from
throughout the range have snout-vent lengths of 20.7 to 29 mm. (25.9
mm.). The smallest individuals are from Costa Rica and Nicaragua (means
24.2 and 24.4 mm., respectively). The largest individuals are from
Guatemala and El Salvador (mean of each 27.0 mm.). The ratio of the
diameter of the tympanum to that of the eye is more than 60 per cent in
most samples, but in those from Costa Rica and British Honduras it is
smaller. The color pattern is highly variable. Some specimens are dark
brown or pale brown in color. Incomplete dorsal stripes are present in
94.6 per cent of the specimens, and transverse bars are present on the
shanks in 98.3 per cent of the specimens. The interorbital spot varies
from transverse to longitudinal in position, and an irregular white
line extends from the upper jaw to the arm in some specimens (Table 7).

_Distribution._--_Hyla staufferi staufferi_ inhabits savanna and
subhumid and xeric forests in the lowlands and moderate elevations from
southern Tamaulipas southward to Nicaragua on the Caribbean versant and
from Guerrero, México to northwestern Costa Rica on the Pacific
lowlands (Fig. 7). Duellman (1963:226) commented that a specimen from
Chinajá, Guatemala, possibly was transported there in the cargo from
Toocog, because with this one exception the species is unknown in
tropical rainforest in Guatemala.

  [Illustration: Fig. 7. Map showing locality records for _Hyla
  staufferi staufferi_ (circles) and _H. staufferi altae_ (dots).]

_Specimens Examined._--México: _Campeche_: 5 km S Champotón KU 71296-7;
7 km W Escárcega, KU 71298-308; 13 km W, 1 km N Escárcega, KU 71309-10,
75090-4. _Chiapas_: 32 km S Arriaga, KU 57789-92; 4 km N Ixtapa, KU
5776-81; 3.6 km SW Las Cruces, KU 37740; 17 km S Las Cruces, KU
57793-4; 24 km S Las Cruces, KU 104160 (tadpoles); 11 km S Tapachula,
KU 57782-8, 60000 (young). _Guerrero_: El Limoncito, near La Venta, KU
31392-401; Mexcala, near Balsa River, KU 31391; Organos, S El Trienta,
KU 31390. _Oaxaca_: 26 km N Matías Romero, KU 33878-82; 2.5 km S
Pochutla, KU 59924-7 (skeletons); 5 km S Pochutla, KU 57795-801; 3.2 km
E Tapanatepec, KU 37877-902; 17.6 km WNW Tapanatepec, KU 65033-4;
Temascal, USC 8243 (8); 3.2 km S Tolocita, KU 39657-8; 0.5 km Tuxtepec,
KU 87073-81, 87610 (tadpoles); 17 km S Tuxtepec, KU 65035-7; 1 km W
Zanatepec, KU 104161 (tadpoles). _Quintana Roo_: Isla Cozumel, 3.5 km N
San Miguel, KU 71710-11 (young). _San Luis Potosí_: Valles, KU 31490.
_Tabasco_: Teapa, UMMZ 118887 (3), 119203 (13); 9.6 km N Teapa, UMMZ
119202; 24 km N Teapa, UMMZ 119961 (5); 29 km N Teapa, UMMZ 119960; 3.5
km S Villahermosa, UMMZ 119201 (2); 17.6 km S Villahermosa, UMMZ 119200
(8). _Tamaulipas_: 1 km E Chamal, UMMZ 110706; Gómez Farías, UMMZ
110701 (3); 5 km SE Gómez Farías, UMMZ 110705; 8 km NE Gómez Farías,
UMMZ 11282 (2), 11283 (3); Kilometer 615 between Río Limón and Llera,
UMMZ 80455 (2); 5 km W San Geraldo, UMMZ 110702 (4), 110703 (3); 8 km W
San Geraldo, near Río Frío, UMMZ 110704 (5). _Veracruz_: 3 km SW Boca
del Río, KU 10494-8; 5 km SW Boca del Río, KU 23701; 5 km ESE Córdoba,
KU 104162 (tadpoles); Cuautlapán, KU 57098-102, 26787; Hacienda
Tamiahua, Cabo Rojo, KU 62871; 2 km ENE Mata Oscura, KU 105627; 5 km SE
Paso del Toro, KU 40144; Portrero Viejo, KU 23911-2, 26786, 27413,
57094-7.

Guatemala: _Alta Verapaz_: Chinajá, KU 57769; Finca La Cubilquitz, UMMZ
90871, 90872 (5), 91379 (2). _Baja Verapaz_: 1 km S San Jerónimo, UMMZ
84077 (7), 84078 (14). _Chiquimula_: 1.6 km SE Chiquimula, UMMZ 98114
(2); Esquipulas, UMMZ 106784 (4), 106785 (14). _El Petén_: No specific
locality, USNM 25143, 24825-6; La Libertad, FMNH 27096-7, KU 57770,
UMMZ 75339 (15), 75340 (15), UMMZ 94341-2. _Esquintla_: 20 km N San
José, AMNH 74369-76. _Guatamala_: 16 km NE Guatamala, KU 43539. Izábal:
Puerto Barrios, TCWC 16671-73, 16646-56; 2.5 km NE Río Blanco, KU
57774-5. _Jalapa_: Jalapa, UMMZ 106788 (44). _Jutiapa_: Finca La
Trinidad, UMMZ 107730 (12), 107731 (16); Jutiapa, UMMZ 106786 (2).
_Zacapa_: 14 km ENE Mayuelas, KU 57773; 7 km ENE Río Hondo, KU 57771-2,
59999 (young).

British Honduras: BELIZE: Belize, FMNH 4406. _El Cayo_: San Agustín,
UMMZ 80741 (8). _Stann Creek_: 10 km S Stann Creek on Hummingbird
Highway, UMMZ 125720-1.

El Salvador: _Cuscatlán_: 7 km WNW Cojutepeque, TNHC 32004-10. _La
Libertad_: 16 km NW Santa Tecla, KU 43540-1. _La Union_: 2.5 km Santa
Rosa, TCWC 16669-70. _Morazán_: Dividendero, USNM 73288-92. _San
Salvador_: San Salvador, FMNH 65101-06, KU 61932-44, 61989-92, 62152
(eggs), USNM 117588, 118391 (3), 118394; 1.6 km NW San Salvador, KU
43162-3.

Honduras: _Atlantidad_: Ceiba, USNM 117592. _Choluteca_: Choluteca, KU
85361-6; 2 km E Choluteca, UMMZ 118395 (7); 3.2 km NE Choluteca, KU
100500-01; 6.2 km E Choluteca, KU 65046-56; 10 km E Choluteca, KU
65045: 5 km S Choluteca, USC 2700 (4). _Colón_: Isla Guanaja (Islas de
la Bahía), TCWC 21551, TNHC 32011. _Cortés_: Agua Azul, TCWC 19178-9;
East side Lago Yojoa, KU 65038-44. _El Paraiso_: Valle de Jamastrán,
AMNH 54800-04. _Francisco Morazán_: Escuela Agrícola Panamericana, AMNH
54963-73; 14.5 km NW Comayaguela, KU 100499; El Zamorano, KU 103224; 29
km N Tegucigalpa, TNHC 32003, 32012.

Nicaragua: _Chinandega_: Finca San Isidro, 10 km S Chinandega, KU
85311-33. _Managua_: 13 km E Managua, KU 85339; 2 km S Tipitapa, KU
85334-8. _Rivas_: 9.5 km SE Rivas, KU 85355-6; 18 km SE Rivas, KU
85354; 7.7 km NE San Juan del Sur, KU 85346-53; 16.5 km NE San Juan del
Sur, KU 85340-5; 5 km SE San Pablo, KU 43151-61. _Zelaya_: Isla Grande
del Maiz, KU 85357-60.

Costa Rica: _Alajuela_: _Los Chiles_, USC 7215 (2), 7217. _Guanacaste_:
4 km W Bagaces, USC 7019 (5); Finca Taboga, KU 102265-5; 12 km S La
Cruz, USC 8091; Las Cañas, KU 41113 (skeleton); 27 km N Las Cañas, USC
8171 (5); Guardia, Río Tempisque, USC 8214; 10 km N Guardia, KU
102266-7; 1.6 km N Guayabo de Bagaces, USC 7023 (3); Liberia, KU
36510-22; 4 km W Liberia, KU 36449-64, USC 102 (10), 103 (9), 104 (7),
105; 6 km N Liberia. USC 8096; 8 km NNW Liberia, KU 65032; 14.5 km N
Liberia, USC 8079, 8138 (2); 14.5 km S Liberia, USC 8238 (5); 6 km N
Nicoya, USC 8229 (11); 4 km S Nicoya, USC 8230, 8231; Peñas Blancas, KU
102263; 8.6 km ESE Playa del Coco, USC 8137 (14); 21 km E Playa del
Coco, USC 8138 (2); Santa Cruz, USC 8232 (2); 3 km E Santa Rosa, TCWC
16663-68; Tenorio, KU 32159; Tilarán, KU 36509. _Puntarenas_: 10 km WNW
Esparta, KU 65022-9, 68614 (skeleton); 4.5 km WNW Esparta, KU 65030; 12
km WNW Esparta, KU 65031; 6 km E Esparta, KU 86477; Hotel Maribella, KU
32157-8; 3 km W Puntarenas, TCWC 16657-62.


_Hyla staufferi altae_ Dunn, New Combination

    _Hyla altae_ Dunn, Occas. Papers Boston Soc. Nat. Hist., 8:61, June
    7, 1933 [Holotype.--MCZ 17972, Summit, Canal Zone, Panamá; Emmett
    R. Dunn collector].

    _Hyla culex_: Stuart, Misc. Publ. Univ. Michigan Mus. Zool., 29:38,
    October 1, 1935. Gaige, Carnegie Inst. Washington Publ., 457:293,
    1936.

    _Hyla staufferi_: Taylor, Univ. Kansas Sci. Bull., 35:862, July 1,
    1952. Duellman, Univ. Kansas Publ., Mus. Nat. Hist., 17:274, June
    17, 1966.

_Diagnosis._--Small frogs (Male to 26 mm., Female to 27 mm.);
dorsolateral and paravertebral stripes complete; longitudinal dark gray
stripe on shank; thighs unmarked; interorbital bar usually absent; toes
about three fifths webbed; gray to brownish gray above.

_Variation._--_Hyla staufferi altae_ is less variable in size,
proportions, and color pattern than is _H. s. staufferi_. The size
varies from 21.7 to 26 mm. (23.6) in 72 males. The ratio of tibia to
snout-vent length is 0.42 to 0.50 (0.45), slightly less than in the
northern subspecies. In color pattern 94.5 per cent of the individuals
have complete dorsal stripes, and all have a longitudinal stripe on the
shank (Table 7).

_Distribution._--This subspecies is restricted to subhumid forests and
savannas on the Pacific lowlands of Panamá. _Hyla s. altae_ is
presently known to occur from Chepo in east-central Panamá through the
Azuero Peninsula to Concepción, Chiriquí, in western Panamá (Fig. 7).

_Specimens Examined._--Panamá: _Canal Zone_: No specific locality, TNHC
24406; 2.8 km SW Fort Kobbe, KU 101679. _Chiriquí_: 14.4 km E
Concepción, AMNH 69799-801; 6.6 km N David, TNHC 32013-4; 2 km S David,
AMNH 68802. _Coclé_: 1 km NE El Caño, KU 101662-75; El Valle de Antón,
AMNH 59601-5, KU 77333-47; 7 km SSW Penonomé, KU 101654-61. _Los
Santos_: Tonosí, KU 101246 (tadpoles), 101697-701. _Panamá_: 2 km WSW
Chepo, KU 101680-8; 6 km WSW Chepo, KU 77324-27; El Cangrejo (Panamá),
KU 101676-8; Nueva Gorgona, AMNH 69991, 69798; 1.5 km W Pacora, KU
77328-32; 2 km N Tocumen, KU 101689-95; 8 km NE Tocumen, KU 101696.




EVOLUTIONARY HISTORY


My assumptions regarding the evolutionary history of the _Hyla rubra_
group in Central America were derived partly from interpretations of the
evolutionary history of other animal groups (Simpson, 1943, 1965; Dunn,
1931b; Stuart, 1950; Duellman, 1958, 1960, 1963, 1965; and Duellman and
Trueb, 1966). The origin and early evolution of the group probably
occurred prior to the Mid-Pliocene in the lowlands of South America,
because the greatest diversity of the group is in Brazil. Differentiation
into two or more subgroups took place in South America prior to the late
Pliocene. At the end of the Pliocene, shortly after the closure of the
Colombian Portal, many South American animals migrated into Central
America (Simpson, 1943, Maldonado-Koerdell, 1964, and Savage, 1966). It
is likely that the _Hyla rubra_ group entered Central America at that
time; apparently two stocks (_rubra-elaeochroa-staufferi_ stock and
_boulengeri-foliamorta_ stock) migrated into Central America.

_Hyla elaeochroa_ is closely related to _rubra_ and probably
differentiated from _rubra_ through spatial isolation. Thus, we have
_elaeochroa_ in Central America and _rubra_ in South America; most
likely only in relatively recent times has _rubra_ migrated into
eastern Panamá from northern South America. The differentiation and
dispersal of _elaeochroa_ and _staufferi_ took place in Central America
after the Pliocene. Probably the events of the Pleistocene resulted in
the isolation of populations. One of these (_Hyla staufferi_ stock) was
restricted in the subhumid Pacific lowlands, whereas the _Hyla
elaeochroa_ stock occupied the tropical wet forests of the Caribbean
lowlands. _Hyla elaeochroa_ apparently more closely resembled the
parental stock by being restricted to the tropical rain forests,
whereas _staufferi_ adapted to subhumid environments and thereby was
able to disperse throughout most of the subhumid regions of Central
America.

After geographical separation took place the initial genetic divergence
between the two populations was maintained by means of ecological and
ethological isolating mechanisms. Under these circumstances it can be
supposed that the different ecological preferences of _elaeochroa_ and
_staufferi_ depend on the climatic changes that took place during the
Pleistocene. On this basis it may be proposed that when the original
prototype broke up into the two incipient species, the _staufferi_
stock became physiologically and behaviorally adapted to subhumid
conditions and dispersed into dry areas of the lowlands of Middle
America. The tropical evergreen forests on the Caribbean side of lower
Central America and the uplift of the Talamanca range in the Pliocene
were barriers to the dispersal of _staufferi_. Consequently, this frog
dispersed along the Pacific lowlands.

At the present time _staufferi_ occupies the length of the Pacific
lowlands in Central America, except in the rainforest of the Golfo Duce
region, which apparently is a relict stand and now separates the ranges
of two subspecies of _Hyla staufferi_. This species crossed the central
Nicaraguan lowlands and reached the Caribbean lowlands of Nicaragua and
nuclear Central America. The species migrated through the subhumid
corridor in northern Honduras and eastern Guatemala (Comayagua Valley
in Honduras and the Motagua Valley of Guatemala) to the Isthmus of
Tehuantepec. Duellman (1960) hypothesized "that during the times of
glacial advances (Pleistocene) the lowlands of the Isthmus probably
were more extensive and had more semiarid tropical environments than at
the present" and that when semiarid environments were continuous from
the Pacific slope across the isthmus to the Gulf lowlands _staufferi_
and other amphibians migrated northward to southeastern Tamaulipas,
México.

_Hyla elaeochroa_ dispersed along Caribbean lowland routes. This
species not only occurs in the wet forests of the Golfo Dulce region
but also in Guanacaste. It is possible that _elaeochroa_ entered
Guanacaste and moved to the Golfo Dulce region when the intervening
area was less xeric than now (Duellman, 1966b). _Hyla elaeochroa_
extended its range to eastern Nicaragua, but even though northeastern
Nicaragua has over 2,000 mm. of precipitation annually (Vivo Escoto,
1964), this species has not spread into Honduras and Guatemala.

_Hyla boulengeri_ is widespread in Amazonian and northern South
America, whereas _foliamorta_ occurs only in eastern Panamá and in
north-central Colombia. The ancestral _boulengeri-foliamorta_ stock
probably invaded Central America in the late Pliocene and dispersed
through humid forested environments to Nicaragua. Apparently a
peripheral population established itself in the dry Pacific lowlands of
Panamá. This population differentiated from _boulengeri_ of the humid
Caribbean lowlands and evolved into _foliamorta_, which subsequently
expanded its range into Colombia.




LITERATURE CITED


BLAIR, W. F.

1960. Mating call as evidence of relations in the _Hyla eximia_ group.
Southwestern Nat., 5(3):129-135. November 1.

BOULENGER, G. A.

1882. Catalogue of the Batrachia Salientia s. Ecaudata, 2nd. ed., pp.
1-503, pls. 1-30. February.

BROCCHI, P.

1881-1883. Etude des batraciens de l'Amerique Centrale. Mission
Scientifique au Mexique et dans l'Amerique Centrale, Liv. 1, pp. 1-122,
pls. 1-21.

COCHRAN, D. M.

1955. Frogs of southeastern Brazil. Bull. U.S. Natl. Mus., 206:1-423.

COPE, E. D.

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_Transmitted February 7, 1969._