In September, 1958, the author and two colleagues collected a large
series of _Pseudemys_ in small ponds and in a river in the basin of
Cuatro Ciénegas, Coahuila. The specimens prove to represent a
previously unrecognized subspecies of _Pseudemys scripta_. The
subspecies is named in honor of Edward Harrison Taylor who has
contributed more than any other person to our present knowledge of
the herpetofauna of México.
=Pseudemys scripta taylori= new subspecies
(Pls. 9-12, Figures 1 & 2)
_Holotype._--Univ. Kansas Mus. Nat. Hist., No. 46952, adult female,
alcoholic; 16 km. S Cuatro Ciénegas, Coahuila, México; 6 September
1958; original number 1694 John M. Legler.
_Paratypes._--A total of 52 specimens as follows (numbers or series
of numbers marked with an asterisk are for specimens prepared as dry
shell with soft parts in alcohol): KU 46932-4*, 46949-51, 46953-67,
46969 (females), 46935*, 46936-48, 46968 (males), same data as
holotype, 6 to 8 September 1958; UU 3416 (male), same locality, 29 to
30 July 1959; KU 46971, 46973* (females), 46972 (male), 46970, 46974
(juveniles), 6 mi. W Cuatro Ciénegas, 3 to 6 September 1958; IU 43585,
43587-9 (females), 43586, 43590 (males), same locality, 11 July 1958;
CNHM 55655 (female), same locality, 22 August 1939; KU 46976 (female),
Río Chiquito, 10 km. S Cuatro Ciénegas, 9 September 1958; UU 3415
(female), 8.5 mi. SW Cuatro Ciénegas, 1 August 1959.
_Diagnosis._--A subspecies of _Pseudemys scripta_ most closely
resembling _P. s. elegans_, but differing from that subspecies in
having: 1) extensive _black_ plastral pattern, all parts of which are
interconnected, covering approximately half of plastron; 2) tendency
toward melanism, in large adults of both sexes, especially noticeable
on posterior part of plastron; 3) cutting edge of lower jaw coarsely
serrate; 4) tendency for femoral edges of plastron to be reflected
ventrally, especially in males; and, 5) pectoral scute longer than
gular.
_Description of holotype_ (measurements given in Table 1).--Carapace
oval in dorsal aspect, slightly narrowed behind, nearly straight
across anterior margin, bluntly serrate behind; shell deep, highly
arched in cross section; height of shell 53 per cent of width; surface
of shell having longitudinal striations; middorsal keel weakly
developed, scarcely discernible except on third central lamina;
lateral margin of carapace not at all reflected, posterolateral
margins flared outward; central laminae all broader than long, the
first urn-shaped.
TABLE 1. MEASUREMENTS (IN MILLIMETERS) OF THE HOLOTYPE
(46952) AND NINE ADULT, TOPOTYPIC PARATYPES OF PSEUDEMYS
SCRIPTA TAYLORI NEW SUBSPECIES. HEIGHT WAS MEASURED IN A
VERTICAL LINE FROM THE CENTER OF THE PLASTRON.
KEY:
A: Collection and Catalogue No.
B: Sex
C: Length of Carapace
D: Width of Carapace
E: Length of Plastron
F: Width of Plastral Forelobe (Humeropectoral)
G: Width of Plastral Hind Lobe (Mid-femoral)
H: Height
I: Width of Head
=================================================================
A | B | C | D | E | F | G | H | I
-----------+----------+-----+-----+-----+-----+-----+-----+------
KU 46948 | [Male] | 179 | 127 | 157 | 71 | 69 | 69 | 28
KU 46941 | [Male] | 148 | 107 | 129 | 59 | 59 | 57 | 25
KU 46968 | [Male] | 139 | 99 | 116 | 55 | 54 | 57 | 25
KU 46937 | [Male] | 128 | 100 | 115 | 54 | 52 | 47 | 21
KU 46944 | [Male] | 105 | 82 | 93 | 46 | 43 | 38 | 19
KU 46932 | [Female] | 214 | 158 | 196 | 86 | 84 | 87 | 37
KU 46952 | [Female] | 202 | 149 | 186 | 87 | 86 | 79 | 33
KU 46957 | [Female] | 188 | 138 | 167 | 79 | 80 | 68 | 31
KU 46959 | [Female] | 156 | 118 | 149 | 71 | 71 | 70 | 29
KU 46962 | [Female] | 132 | 101 | 119 | 58 | 53 | 51 | 24
-----------+----------+-----+-----+-----+-----+-----+-----+------
Ground color of carapace (hereinafter, colors are those of preserved
specimen) dark olive; upper surface of each marginal scute having
round or oval black mark, two such marks on each marginal of first
pair; marks on margin of anterior half of carapace having pale
orange-yellow borders, marks more posteriorly having indistinct
borders or no border; upper surface of carapace having numerous,
irregularly arranged black marks on a faint reticulum of pale lines;
one or two large oval marks on each lateral scute arranged more or
less vertically, other marks on laterals irregular in size and
arrangement; central scutes having three to five longitudinally
arranged, narrow black marks on each scute.
Ground color of plastron pale yellow, anterior half extensively marked
with black along laminal seams; all plastral markings interconnected;
undersurfaces of marginals on anterior half of shell having pale
centers; undersurfaces of posterior marginals and posterior half of
plastron solid black.
Plastron more or less evenly rounded in front, slightly indented on
gular border; posterolateral free edge of plastron reflected slightly
downward; posterior border of plastron having wide shallow anal notch;
plastral laminae, in order of length--abdominal, anal, pectoral,
gular, femoral, humeral; abdominal lamina longer than combined lengths
of pectoral and humeral or humeral and gular.
Head moderately wide; snout slightly pointed in dorsal view, curving
evenly backward and downward from nostrils in profile; upper jaw
notched in middle, cutting edges finely and unevenly serrate, crushing
surfaces having distinct ridge bearing fine denticulations but no
large teeth; cutting edges of lower jaw coarsely and evenly serrate,
tooth at symphysis relatively large; raised ridges of lower crushing
surfaces each having low blunt tooth and many fine denticulations.
Major markings of head and neck as follows: narrow stripe beginning
at posterior edge of eye and extending downward and backward (across
tympanum) on side of neck to shoulder (stripe wider behind than at
origin); wide stripe from lower posterior corner of eye extending
downward, across mandibular articulation (and below tympanum) on
throat to shoulder (wider at origin than behind); postorbital mark,
four to five millimeters wide, approximately 26 millimeters long,
connected to eye by narrow isthmus anteriorly and continuous with
narrow stripe on upper part of neck posteriorly; stripe on mandibular
symphysis widened and bifurcated posteriorly, its two branches
enclosing one wide and two narrow stripes; wide stripe beginning
in middle of mandibular ramus and running backward to point below
mandibular articulation on each side; top of head, sides of snout, and
areas between above-mentioned major stripes, marked with numerous,
fine, often indistinct pale lines.
Pale dorsal stripe on fleshy portion of each finger, those of second
and fourth fingers continuous to mid-humeral region, those of other
fingers broken on anterior face of antebrachium; upper and lower pale
stripes of antebrachium joined in mid-humeral region.
_Coloration of living specimens._--Ground color of soft parts dark
olive to slate gray or black; ground color of carapace olive to
slate gray; ground color of plastron pale yellow, markings blackish,
tinged with brown in younger specimens, sooty black in most adults.
Postorbital mark red; other markings on soft parts cream to buffy
yellow.
_Geographic range._--_Pseudemys scripta taylori_ is known only from
ponds, and the Río Chiquito in the basin of Cuatro Ciénegas. The
discovery of _taylori_ brings to six the number of valid subspecies
of _scripta_ known in México (_elegans_, _gaigeae_, _hiltoni_,
_nebulosa_, _ornata_, and _taylori_) and to three (_elegans_,
_gaigeae_, and _taylori_) the number known in Coahuila. My own
studies of these six subspecies indicate that they are, beyond
reasonable doubt, members of a single polytypic species (_scripta_).
I tentatively follow Williams (1956:153) in rejecting "_cataspila_"
as an invalid name.
Three specimens of _Pseudemys scripta_ obtained by Robert G. Webb in
the Río Chiquito at a point 8 mi. W of Nadadores, 2100 ft., where the
river flows out of the basin of Cuatro Ciénegas, have many
characteristics in common with _taylori_, but resemble _elegans_
closely in several characters as follows: no extensive melanism;
plastral markings tending to be brownish; anterior plastral markings
smudgelike, isolated or nearly isolated; markings on lateral scutes
tending to have vertical, linear arrangement; cutting edge of mandible
weakly serrate; femoral edges of plastron not reflected ventrally; one
or more fine, pale lines between two major stripes on antebrachium;
gular longer than pectoral in one specimen, longer than femoral in
both specimens. The nature of these specimens suggests that parts of
the Río Salado drainage north and east of Cuatro Ciénegas are in a
zone of intergradation between _taylori_ and _elegans_. I have
examined what I consider to be typical examples of _P. s._ _elegans_
from the region of Múzquiz (CNHM 28843-45, 55625-45), and from Don
Martín Reservoir (KU 33524). These localities are, respectively,
approximately 70 miles north-northeast and 100 miles east-northeast of
Cuatro Ciénegas. The specimens from Múzquiz are presumably the same
that Carr (1952:262) treated as "... _elegans-cataspila_ intergrades,
but with a strong leaning toward eastern _elegans_...." Populations of
_P. scripta_ in central eastern Coahuila (between the above-mentioned
localities and Cuatro Ciénegas) probably are a conglomerate of only
two subspecies (_elegans_ and _taylori_), not including _gaigeae_ (as
was suggested by Hamilton, 1947:65 and by Carr, op. cit.:241, map
17;262).
Specimens reported by Schmidt and Owens (1944:101) as _P. s. gaigeae_
(from several localities in the region mentioned above) have been
examined in the course of my study and prove to be _P. floridana
texana_. A specimen reported by Shannon and Smith (1949:399; IU 4094,
Hidalgo Co., Texas) as being either _gaigeae_ or an _elegans-gaigeae_
intergrade, has been examined and is here regarded as a typical
specimen of _elegans_. I regard _P. s. gaigeae_ as a subspecies of the
upper Río Grande and disrupted parts of that drainage; the range of
that subspecies meets that of _P. s. elegans_ somewhere between the
Big Bend region and Piedras Negras. In any event, the influence of
_gaigeae_ is not so widespread as other authors (Carr, _loc. cit._;
Hamilton, _loc. cit._; Hartweg, 1939:3-4) have indicated.
Further collecting in the Río Salado and its tributaries east and
north of Cuatro Ciénegas will be necessary before the exact range of
_P. s. taylori_ can be determined.
_Variation._--Characteristics ascribed to the holotype pertain in
general to all specimens in the hypodigm, except as noted below. The
postorbital mark is in contact with the eye on one or both sides in 46
per cent of the specimens (narrowly separated from eye in remainder)
and is in contact with a neck stripe (on one or both sides) in 35 per
cent of the specimens. The pattern of the antebrachium is as shown in
Fig. 2 in all specimens except that the thin lateral stripe is
obliterated by melanism in older specimens of both sexes. The lateral
edges of the posterior plastral lobe are reflected downward, at least
slightly, in all but one specimen (an adult, kyphotic female). The
first central lamina is straight-sided in juveniles and becomes
urn-shaped only in adults. The relative height of the shell tends to
increase with a general increase in size in both sexes.
[Illustration: FIG. 1. _Pseudemys scripta taylori_ new
subspecies: left side of head, female paratype (KU 46933),
× 1.]
[Illustration: FIG. 2. _Pseudemys scripta taylori_ new
subspecies: anterior view of left antebrachium, female
paratype (KU 46934), × 1.]
_Comparisons._--Of the five other subspecies of Mexican _P. scripta_
mentioned above, three subspecies (_gaigeae_, _hiltoni_, and
_nebulosa_) form a natural group herein referred to as the _gaigeae_
group. _Pseudemys s. taylori_ is distinguished from members of the
_gaigeae_ group by elongate, red postorbital mark (yellow or orange in
the _gaigeae_ group), extensive black plastral pattern (narrow--or if
wide, brownish--in _gaigeae_ group), and serrate lower jaw (nearly
smooth in _gaigeae_ group).
The subspecies _P. scripta taylori_ differs from _P. scripta elegans_
as indicated in the following comparative list of characteristics:
_P. s. taylori_ _P. s. elegans_
1. Extensive black plastral 1. Plastral pattern consisting
pattern, all parts of which of separate brown smudges (at
are interconnected. Plastral least anteriorly). Plastral
pattern partly obliterated by pattern obliterated by
melanism in old individuals melanism only in adult males.
of both sexes.
2. Markings of carapace in form 2. Markings of carapace having
of indistinct ocelli. linear and vertical.
3. Cutting edge of mandible 3. Cutting edge of mandible
serrate. smooth.
4. Foreclaws of mature males 4. Foreclaws of mature males
unmodified. greatly elongated.
5. Gular shorter than pectoral 5. Gular longer than pectoral
(91 per cent of specimens), (90 per cent of specimens)
gular and femoral subequal. and longer than femoral (all
specimens).
6. Shell relatively higher, 6. Shell relatively lower,
posterior lobe of plastron posterior lobe of plastron
relatively narrower (Fig. 3). relatively wider (Fig. 3).
7. Lateral edges of posterior 7. Lateral edges of posterior
plastral lobe reflected plastral lobe unmodified.
downward.
Four specimens of _P. s. ornata_ (MCZ 46392-3, 46397, 46400, two adult
females and two adult males) from the Río Soto la Marina drainage of
Tamaulipas differ from _P. s. taylori_ as follows: plastral pattern
diffuse and brownish, not black; gular longer than pectoral; cutting
edge of lower jaw only slightly serrate; stripe on mandibular
symphysis isolated, not joined with ventral neck stripes to form
inverted Y; postorbital stripe (yellow in preservative) connected to
eye by narrow isthmus and continuous with neck stripe to shoulder.
In _P. s. taylori_ there is an obtuse ridge or prominence across the
bridge, on a line joining the free lateral edges of the plastron; the
area between the ridges is nearly flat. The bridge forms a distinct
plane on each side between the mentioned ridge and the outer edges of
the marginals. In cross section this plane forms an angle of 30 to 45
degrees with the horizontal plane of the plastron. The higher bridge
and deeper shell of _taylori_ result in a slightly higher center of
gravity in this subspecies than in the specimens of _elegans_ and
_ornata_ I have examined. In the two subspecies last named the
longitudinal ridges on the plastron are indistinct or wanting and the
bridge forms a lesser angle with the horizontal plane of the plastron.
The largest female of _taylori_ (218 mm.) is shorter by some 30 mm.
than the smaller female in the series of _ornata_ from Tamaulipas
whereas the largest male of _taylori_ (179 mm.) is shorter by some
80 mm. than the smaller male from Tamaulipas. _Pseudemys s. taylori_
probably is smaller, on the average, than either _elegans_ or northern
populations of _ornata_.
There seems to be no reliable published record of the color of
the postorbital mark in living examples of _P. s. ornata_ from
Tamaulipas. Williams (1956:147, 154) indicated that this color may be
red or yellow for Mexican and Central American populations of _ornata_
in general and Günther (1885: Pl. 6 b) indicated that the color
was yellow in _Emys cataspila_; however, both of the observations
mentioned were presumably based on preserved rather than living
specimens. The postorbital marks of a live specimen of _ornata_
(KU 40131) from southern Veracruz were yellowish to buffy with a
pinkish tinge anteriorly (_fide_ notes of Robert G. Webb and a color
photograph by him).
[Illustration: FIG. 3. Relative height of shell (expressed
as a percentage of width) and relative width of posterior
plastral lobe (expressed as a percentage of plastral length)
in two subspecies of _Pseudemys scripta_. The data presented
are for 62 specimens (40 [Female], 22 [Male]) of _P. s.
taylori_ and 37 specimens (13 [Female], 24 [Male]) of _P. s.
elegans_. Horizontal and vertical lines represent the mean
and range, respectively, whereas open and solid rectangles
represent one standard deviation and two standard errors of
the mean, respectively.]
[Illustration: PLATE 9
_Pseudemys scripta taylori_ new subspecies: dorsal view of
holotype (KU 46952), approximately 11/16 natural size.]
[Illustration: PLATE 10
_Pseudemys scripta taylori_ new subspecies: ventral view of
holotype (KU 46952), approximately 11/16 natural size.]
[Illustration: PLATE 11
Paratypes of _Pseudemys scripta taylori_ new subspecies:
_Left_--dorsal and ventral views of KU 46943, male, 16 km. S
Cuatro Ciénegas, × 3/8; _Upper right_--KU 46974, juvenile, 6
mi. W Cuatro Ciénegas, × 5/6; _Lower right_--KU 46968, male,
16 km. S Cuatro Ciénegas, × 3/8.]
[Illustration: PLATE 12
Ventral views of four subspecies of _Pseudemys scripta_:
_Upper left_--_P. s. ornata_ (KU 40131 [Female]), Río
Playa Vicente, San Andrés Tuxtla, Veracruz, × 1/3; _Upper
right_--_P. s. gaigeae_ (IU 43583 [Female]), 1 mi. E La Cruz,
Chihuahua, × 3/8; _Lower left_--_P. s. elegans_ (CNHM 55627
[Male]), Múzquiz, Coahuila, × 2/3; _Lower right_--_P. s.
taylori_ new subspecies (KU 46970 juvenile), paratype, 6 mi.
W Cuatro Ciénegas, Coahuila, × 11/16.]
_Natural history._--Specimens of _P. s. taylori_ were caught in hoop
nets in clear deep pools and in the Río Chiquito. No specimens were
collected or observed in marshy situations where the water was shallow
or stagnant. Individuals were seen only near dusk and in early morning
when a number floated just below the surface with only their heads
showing. They were never seen on land during our short stay in the
basin. The few stomachs that were opened contained vegetable material.
In terms of number of specimens trapped, _P. s. taylori_ was the most
abundant turtle in pools at and near the type locality (Webb and
Legler, 1960).
_Relationships and phylogeny._--The basin of Cuatro Ciénegas now
drains, via the Río Salado, into the lower Río Grande. Brief
descriptions of habitats and topography in the basin are given by
Gilmore (1947:148-150, fig. 2) and Webb and Legler (1960). In the more
northern parts of the Salado drainage (for example, in the Río Sabinas
near Múzquiz) slider turtles are typical _P. s. elegans_. Assuming
that conditions which permit genetic exchange between populations of
turtles in the Salado drainage system differ in no major respect from
conditions in other parts of the range of _Pseudemys scripta_, it is
logical to suppose that the differentiation of _P. s. taylori_ at
Cuatro Ciénegas was preceded by the isolation of a population in that
basin.
The Río Chiquito drains through a narrow gap in the northeastern end
of the basin of Cuatro Ciénegas. Interruption of this stream would
effectively isolate aquatic habitats in the basin.
It is here proposed that _P. s. taylori_ is a relict of an earlier,
lower Río Grande stock, part of which became isolated in the basin of
Cuatro Ciénegas in postpluvial times. The morphological similarity of
_P. s. taylori_ and _P. s. elegans_ indicates that both were derived
from this parent stock; similarity of both subspecies to populations
of _P. s. ornata_ in Tamaulipas suggests that the latter subspecies
may also be a derivative of the mentioned stock of the lower Río
Grande.
The proposed former isolation of the basin of Cuatro Ciénegas is
supported by evidence found in studies of other turtles in the basin.
Of the four kinds of turtles known to occur there (_Terrapene
coahuila_, _P. s. taylori_, _Trionyx spinifer emoryi_, and _Trionyx
ater_), all but _T. spinifer_ seem to be endemic. These three kinds
comprise a graded series, in regard to their degree of differentiation
from closest known relatives, as follows: 1) _Terrapene coahuila_ is
morphologically the most generalized and primitive of living box
turtles; the species is unique in its highly aquatic mode of life (see
Legler, 1960:532-534, for brief discussion of relationships within
genus Terrapene); 2) _Trionyx ater_ seems to represent a relict
population of pre-_Trionyx spinifer_ stock; presumably, _spinifer_ has
reinvaded the basin of Cuatro Ciénegas in relatively recent times
and, as noted above, _spinifer_ and _ater_ now occur sympatrically (at
least in a geographic sense) in the basin (Webb and Legler, _op.
cit._); and, 3) evidence presented above suggests that _P. s. taylori_
intergrades with _P. s. elegans_ outside the basin.
The three endemic populations of turtles at Cuatro Ciénegas therefore,
differ by varying degrees from their closest living relatives. This
variation in degree of difference possibly results from varying
periods of isolation. Probably the basin of Cuatro Ciénegas has been
isolated from, and reconnected to, the lower Río Grande drainage at
several times in the past. The relationships of fishes in the basin,
now under study by other workers, also suggest that the basin was
isolated more than once.
_Remarks._--Local names for the above-mentioned localities in the
basin of Cuatro Ciénegas are as follows: Anteojo (6 mi. W Cuatro
Ciénegas); El Mojarral (8.5 mi. SW); and Ojo de Agua de Tío Candido,
on Rancho Orozco (16 km. S). The Río Chiquito is referred to by some
natives as "Río Colorado" and by some as "Río Salado." The local name
for _P. s. taylori_ is _tortuga negra_ (the name is used also for
_Terrapene coahuila_).
_Acknowledgments._--For permission to examine specimens in their care,
I wish to thank Doris M. Cochran, Smithsonian Institution (USNM),
Ernest E. Williams, Museum of Comparative Zoology (MCZ), Rollin H.
Baker, Michigan State University (MSU), Hobart M. Smith, University of
Illinois (IU), and Robert F. Inger, Chicago Natural History Museum
(CNHM). Pete S. Chrapliwy, John K. Greer, Robert G. Webb, and Kenneth
L. Williams all contributed field data concerning the specimens of
_P. s. taylori_ that they collected. I am especially grateful to Webb
for donating two specimens to the University of Utah (UU). Special
gratitude is expressed to Wendell L. Minckley and Robert B. Wimmer
for assistance with field work at Cuatro Ciénegas. Daniel Rodríguez,
Cuatro Ciénegas, guided us to the various ponds at and near the type
locality. Robert R. Miller, Robert G. Webb, and Donald Tinkle read the
manuscript and offered helpful criticisms. Figures 1 and 2 were drawn
by Lorna Cordonnier.
_Comparative materials examined_ (total of 135 specimens).--_P. s.
elegans_ (52 specimens): KU 2897-8, 3195, 18337, 18341, 18345, 18347,
18364, 45027-31, 45033, 46750, 46863, and John M. Legler 1394 and
1435, various localities, Kansas; KU 16400, Howard Co., Texas; KU
39983-4, 8 mi. N and 2 mi. W Piedras Negras, Coahuila; KU 33525,
33527-9, La Gacha, Coahuila; CNHM 28843-5, 55625-45, Rancho las
Ruscias, Múzquiz, Coahuila; KU 39982, 2 mi. S and 3 mi. E San Juan de
Sabinas, Coahuila; KU 33524, Don Martín Reservoir, Coahuila; _P. s.
elegans_ × _taylori_ (3): KU 53785-7, 8 mi. W. Nadadores, Coahuila;
_P. s. gaigeae_ (39): MCZ 54724, Elephant Butte Reservoir [Sierra or
Socorro Co.], New Mexico; KU 51158-61, 51202-3, Lajitas, Brewster Co.,
Texas; KU 51162-6, 51204-6, 51315, 1 mi. NW Ojinaga, Chihuahua; KU
33884, 51167-72, 51207-20, 3 mi. N and 5 mi. E Meoqui, Chihuahua; IU
43583-4, La Cruz, Chihuahua; _P. s. ornata_ (9): MCZ 46392-3, Río
Purificación, Rancho Sta. Ana, Tamaulipas; MCZ 46397, E of Güémez,
Tamaulipas; MCZ 46400, Jiménez, Tamaulipas; KU 40161-2, Alvarado,
Veracruz; KU 40131, San Andrés Tuxtla, Veracruz; V. E. Thatcher 98, 15
mi. N Teapa, Tabasco; KU 40139, Cantemo[c], Tabasco; _P. s. taylori_
(23 in addition to type series): KU 51438, 51442, 53788-53801
topotypes; KU 53802-5, 8.5 mi. SW Cuatro Ciénegas, Coahuila; KU
51439-41, 10 km. S Cuatro Ciénegas, Coahuila; _P. floridana texana_
(10 from Coahuila): KU 39985, 2 mi. W Jiménez; CNHM 55654, Allende;
CNHM 55646, Cd. San Juan; CNHM 55648, Hermanas; CNHM 55649-53,
Lampacitas; KU 33526, Don Martín Reservoir.