A New Subspecies of Slider Turtle
(Pseudemys scripta) from Coahuila, México

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.

Ground color of carapace (hereinafter, colors are those of preserved specimen) dark olive; upper surface of each marginal scute having round or oval [Pg 76] 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.

[Pg 77] 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. [Pg 78] 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.

Fig. 1. Pseudemys scripta taylori new subspecies: left side of head, female paratype (KU 46933), × 1.

Fig. 2. Pseudemys scripta taylori new subspecies: anterior view of left antebrachium, female paratype (KU 46934), × 1.

[Pg 79]

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:

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 [Pg 80] 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).

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.