Miniaturization in Direct-Developing Frogs from Mexico with the Description of Six New Species
Author
Jameson, Tom J. M.
Author
Streicher, Jeffrey W.
Author
Manuelli, Luigi
Author
Head, Jason J.
Author
Smith, Eric N.
text
Herpetological Monographs
2022
2022-04-04
36
1
1
48
http://dx.doi.org/10.1655/0733-1347-36.1.1
journal article
10.1655/0733-1347-36.1.1
6518587
Craugastormexicanus
(
Brocchi 1877
)
Leiuperus mexicanus
Brocchi 1877:184
. Holotype unsexed (
MNHNP 6218
) from ‘‘
Mexico
’’ (
¼
Cerro San Felipe,
Oaxaca
,
Mexico
[
Smith and Taylor
1950
]). [Examined].
Paludicola mexicana
(Brocchi)
:
Boulenger 1882:237
;
Neiden 1923:513
.
Pleurodema mexicana
(Brocchi)
:
Parker 1927:475
.
Microbatrachylus oaxacae
Taylor 1940:505
.
Holotype
male (
FMNH
100001) from ‘‘Cerro San Flipe, near
Oaxaca
,
Oaxaca
,
Mexico
.’’ [Examined].
Microbatrachylus lineatissimus
Taylor 1941:87
.
Holotype
male (
FMNH
1000036) from ‘‘Cerro San Flipe, near
Oaxaca
,
Oaxaca
,
Mexico
.’’ [Examined].
Microbatrachylus fuscatus
Davis and Dixon 1957:146.
Holotype
female (
TCWC
12171) from ‘‘
20 miles
east of Tulancingo,
Hidalgo
,
Mexico
.’’ [Not examined; neartopotypic specimen from
Hidalgo
examined (
UTA
A-66138
)].
Eleutherodactylus oaxacae
(Taylor)
:
Lynch 1965:3
.
Eleutherodactylus lineatissimus
(Taylor)
:
Lynch 1965:3
.
Eleutherodactylus mexicanus
(Brocchi)
:
Gorham 1966:86
.
Craugastor mexicanus
(Brocchi)
:
Crawford and Smith 2005:536
.
Diagnosis.
—Based on
26 specimens
. Aspecies of
Craugastor
distinguished by the following combination of characters: (1) large adult size (maximum SVL
¼
40.5 mm
); (2) full ossification of the skeleton in adults; (3) presence of posterolateral projection of frontoparietal (
Fig. 26B
); (4) presence of vomerine odontophores (in larger individuals); (5) presence or absence of raised tubercles on eyelids, <4 smooth to round and only slightly protruding tubercles; (6) supratympanic fold developed; (7) face flank, labium barred with or without distinctive canthal stripe; (8) one (or two fused) postrital tubercles; (9) gular region peppered with melanocytes; (10) dorsal surface extremely variable, ranging from dark or light stripes, dark hourglass, dark or pale dorsal stripe of different widths, being unicolored dark or pale brown, to bird-dropping coloration (black peppered grayish dorsum with a dirty white medial streak and bright-white heels), all color morphologies have variable presence of interocular band and suprascapular or rump blotching or stripping; in most snout colored as rest of body but sometimes pale; (11) variable middorsal ridge; (12) dorsal skin smooth or tubercular and may have hourglass and/or vertebral and/or paravertebral ridges; (13) body flank unicolored pale, slightly darker anteriorly, or spotted posteriorly and or anteriorly, supratympanic dark coloration sometimes reaching posterior axillary area; smooth to shagreened; (14) inguinal gland present and axillary gland sometimes present in adults; (15) when leg adpressed to body, heel reaches snout tip or beyond; (16) outer tarsal ridge with 0–5 rounded tubercles; smooth or with thick but only slightly raised fringe; (17) finger and toe tips round and expanded (rarely slightly spatulate or barely expanded and somewhat pointed); (18) inner metatarsal tubercle larger than outer metatarsal tubercle.
Comparisons.
—
Craugastor mexicanus
can be differentiated from
C. candelariensis
,
C. cueyatl
,
C. hobartsmithi
,
and
C. portilloensis
by the equal sizes of the inner and outer metatarsal tubercles (unequal sizes in
C. mexicanus
). It can be differentiated from
C. bitonium
and
C. pygmaeus
by the absence of a posterolateral projection of the frontoparietal (present in
C.
mexicanus
). It can be differentiated from
C. polaclavus
and
C. rubinus
by the absence of vomerine odontophores (present in
C. mexicanus
). It can be differentiated from
C. montanus
by the condition of supratympanic folds in adults; developed in
C. mexicanus
versus moderate to poorly developed in
C. montanus
. It can be differentiated from
C. omiltemanus
by ventral skin texture in life; smooth to granular in
C. mexicanus
versus areolate in
C. omiltemanus
.
Craugastor mexicanus
is most similar to
C. saltator
. We were unable to identify any reliable morphological characters to differentiate
C. mexicanus
and
C. saltator
;
however, they have nonoverlapping geographic distributions, with
C. saltator
only occurring in western
Guerrero
(
Fig. 6
).
Description.
—In previous literature, described as largebodied, long-legged with row of small tubercles on outer edge of the tarsus (
Taylor 1941
); variable palmar tubercle arrangements (palmar tubercle divided, single, or evaginated;
Lynch 1965
); inner metatarsal tubercle larger than outer metatarsal tubercle; lack of tarsal tubercles (
Lynch 2000
).
Holotype
(MNHNP 6318) is large (~
40 mm
SVL); owing to poor preservation, columella of
holotype
partially ruptured the tympana on both sides (
Fig. 1B
); finger lengths III> IV> II> I; toe length IV> V
¼
III> II> I.
Distribution.
—This species is widespread throughout eastern
Mexico
in high-elevation habitats (
1554–2700 m
) of
Oaxaca
,
Puebla
,
Hidalgo
, and
Veracruz
(
Fig. 6
). These habitats span the Sierra Madre Oriental and Sierra Madre del Sur.
Canseco Márquez and Gutiérrez Mayén (2010)
report that
C. mexicanus
occurs in the forests adjacent to the Tehuacán-Cuicatlán Valley in
Puebla
and
Oaxaca
. It is likely this species occurs in
Guerrero
; however, most specimens resembling
C. mexicanus
we examined from
Guerrero
are referrable to
C. saltator
.
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04 May 2022
FIG. 27.—Examples of intraspecific polymorphism in
Craugastor mexicanus
from Mexico; female (A, UTA A-56558, SVL
¼
37.3 mm) from Putla de Guerrero municipality; Oaxaca, female (B, UTA A-64415, SVL
¼
28.3 mm) from Carretera Sola de Vega–Juquila, Oaxaca; subadult (C, UTA A-64271, SVL
¼
11.9 mm) from Carretera Sola de Vega–Juquila, Oaxaca; subadult and adult (D, UTA A-64258, SVL
¼
13.6 mm and MZFC-HE-35584, SVL
¼
unavailable) both from 8.1 mi south of Sola de Vega, Oaxaca; adult (E, UTA A-66107, SVL
¼
unavailable) from Carretera Sola de Vega–Juquila, Oaxaca; subadult (F, UTA A-64260, SVL
¼
16.6 mm) from Carretera Sola de Vega–Juquila, Oaxaca; female (G, UTA A-64413, SVL
¼
23.5) from Sierra Miahuatlán, Oaxaca; female (H, UTA A-56579, SVL
¼
21.3 mm) from Sierra Negra, Puebla; female (I, UTA A-56559, SVL
¼
35.4 mm) from Sierra Mazateca, Puerto Soledad, Oaxaca; subadult (J, UTA A-64257, SVL
¼
17.6 mm) from Sierra Mixe, Carretera Ayutla–Zacatepec, Oaxaca; subadult (K, UTA A-64259, SVL
¼
10.9 mm) from 6.1 mi south of San Miguel Suchixtepec, Oaxaca; subadult (L, UTA A-66138, SVL
¼
unavailable) from 20 mi east of Tulancingo, Hidalgo. Acolor version of this figure is available online.
Phylogenetics.
—The concatenated data set placed
C. mexicanus
as the sister taxon to a clade of
C. omiltemanus
þ
C. saltator
with high support in the BAYES analysis (0.98) but moderate support in the ML analysis (75;
Fig. 3
). This appears to be a relationship supported exclusively by the mtDNA data set because separate analysis of the nDNA markers did not confidently infer a sister taxon of
C. mexicanus
(
Figs. 4
and
5
). Although BAYES analyses strongly supported the monophyly of
C. mexicanus
(> 0.90), the ML analyses recovered variable support ranging from 79 (concatenated analysis) to 54 (nDNA-only analysis). In terms of genetic distances (
Table 4
),
C. mexicanus
was most similar to
C. omiltemanus
(4.9%), followed by similarity to
C. saltator
(5.1%).
Intraspecific variation.
—We examined over
220 specimens
of
C. mexicanus
for this revision (Appendix I), and briefly provide some patterns of intraspecific variation that we observed. Many populations have substantial colorpattern polymorphism (
Fig. 27
), similar to what is observed in the
C. rhodopis
series (
Lynch 1966
;
Streicher et al. 2014
). In some northern populations (
Hidalgo
and
Puebla
), the canthal mask is broken into a black spot posterior to the tympanum (often with a thin yet distinctive white margin). Specimens throughout
Oaxaca
varied in whether they had a single or divided palmar tubercle (as reported by
Lynch 1965
, see his
Fig. 2
); in
six specimens
we examined there was asymmetry with a single palmar tubercle on one hand and divided on the other.
Patterns of dorsal ridging and coloration often coincide, with observations of the following morphs: (1) straight raised ridges that are tubercular and darker in coloration than the rest of the dorsum; (2) straight raised dorsal ridges that are tubercular but of the same color as the rest of the dorsum; (3) straight lines of color that are dark but with no tubercular raised ridges; (4) ridges that are not straight but form an hourglass shape and are tubercular; (5) ridges that are not straight but form an hourglass shape and are not tubercular; (6) scattered tubercles on the dorsum, which are sometimes dark and sometimes same color as the background; (7) pale or dark unicolored dorsum; (8) a unicolored dorsum with a pale median stripe that can be ridged or smooth; (9) a wide dark band on the dorsum, which usually co-occurs with a pale upper labium; and, (10) white hills of coloration and a peppered grayish dorsum sometimes with a diffused lighter cream color, a pattern that may mimic bird droppings (appearing superficially as a smear of uric acid and digestive waste).
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Remarks.
—The skull of
C. mexicanus
is similar to that of
C. omiltemanus
and
C. saltator
,
with more anteriorly placed anterior suture of the frontoparietal and prootic than in other species. We noticed that the ‘‘
M. lineatissimus
’’ morphotype (raised and parallel ridges on the dorsum) occurs widely throughout the range of
C. mexicanus
. Interestingly, the examined
paratype
of ‘‘
M. lineatissimus
’’ has a unique skull shape for
C. mexicanus
. The shape is similar to that of
C. hobartsmithi
,
C. montanus
,
and
C. pygmaeus
,
with a more posteriorly placed anterior suture of the frontoparietal and prootic than in other species, coupled with a narrower back of the skull than in any other species (
Fig. 27A
). This unique condition likely explains the specimen as an outlier in several of our statistical analyses (
Figs. 9
,
11
, and 12). However, we were unable to CT-scan other individuals with the ‘‘
M. lineatissimus
’’ morphotype (or the
holotype
of
M. lineatissmus
), so future investigation is necessary to determine whether the examined
paratype
(FMNH 104548) is an aberrant individual of
C. mexicanus
or represents a valid taxon.
Lynch (1965)
reports that ‘‘
E. oaxacae
’’ has parotoid glands. However, we saw no evidence of these glands in the
two type
specimens that we examined (FMNH 100001 and FMNH 126638), nor are we aware of any species of
Craugastor
that possess parotoid glands (
¼
large poison glands on the nuchal region).
Craugastor mexicanus
likely co-occurs with
C. omiltemanus
at high-elevation localities of central
Oaxaca
(
Figs. 6
and
8
). At intermediate elevation localities in
Veracruz
and
Oaxaca
, it may overlap with
C. pygmaeus
(
Fig. 7
). Male
C. mexicanus
have significantly larger tympana than do female
C. mexicanus
(
Fig. 13
).