Each of the external morphological characters used in the systematic
treatment of _Ptychohyla_, as well as the nature of the tongue,
is discussed below.
SIZE AND PROPORTIONS.--Comparisons of size and certain proportions are
given in Table 1. Frogs of this genus are small; the largest specimen
examined is a female of _P. euthysanota euthysanota_ having a
snout-vent length of 53.3 mm. The species comprising the _Ptychohyla
schmidtorum_ group are smaller; the largest specimen examined is a
female of _P. schmidtorum schmidtorum_ having a snout-vent length of
38.0 mm. An analysis of the various measurements and proportions shows
few constant differences. _Ptychohyla ignicolor_ differs from all of
the other species in having the head slightly wider than long and the
tympanum noticeably less than half the size of eye. _Ptychohyla
spinipollex_ has a relatively narrow interorbital distance,
approximately equal to the width of the eyelid, whereas in all of the
other species that distance is much more than the width of the eyelid.
SNOUT.--All species have a blunt snout. In _P. leonhardschultzei_ and
_P. ignicolor_ the snout is nearly square in lateral profile; in _P.
schmidtorum_ the snout is slightly rounded above and below, and in the
other species it is rounded above. _Ptychohyla leonhardschultzei_ and
_P. spinipollex_ have a vertical fleshy rostral keel on the snout; in
these species, because of this keel, the snout in dorsal profile is
pointed. The nostrils are slightly protuberant in all species, and in
_P. schmidtorum_ the internarial region is slightly depressed.
HAND.--The species in the _Ptychohyla euthysanota_ group have a
vestige of web between the first and second fingers; the other fingers
are about one-third webbed. Breeding males have a cluster of horny
nuptial spines on the thumb. The spines are largest in _P. spinipollex_
(Fig. 1) and vary in number from 35 to 66 (average 47.4) on each thumb.
In the other species of the _Ptychohyla euthysanota_ group the spines
are smaller and usually more numerous; the numbers of spines on each
thumb (means in parentheses) in members of this group are: _P.
euthysanota euthysanota_, 44-143 (83.8); _P. euthysanota
macrotympanum_, 40-110 (63.0); _P. leonhardschultzei_, 24-80 (54.7).
The species in the _Ptychohyla schmidtorum_ group have no web between
the first and second fingers and only a vestige of web between the
other fingers. Furthermore, these species lack nuptial spines in
breeding males. Like the usual horny excrescences on the thumbs of
many species of frogs, the horny spines on the thumbs of members of
the _Ptychohyla euthysanota_ group are seasonal in development.
TABLE 1.--VARIATION IN CERTAIN CHARACTERS IN THE SPECIES OF PTYCHOHYLA.
(MEANS ARE IN PARENTHESES BELOW THE RANGES.)