North American Recent Soft-shelled Turtles (Family Trionychidae) Part 15

Surface of carapace in hatchlings uniform pale brown or tan; small white tubercles absent or inconspicuous on anterior half of carapace, but evident on posterior half of carapace, sometimes well-defined (TU 481), but usually inconspicuous (TU 678, 490); pale rim of carapace less than four times wider posteriorly than laterally.

Adult males resembling description of holotype; small whitish tubercles or dots rarely two millimeters in diameter on posterior half of carapace, smaller and usually inconspicuous on anterior half of carapace (TU 13281, 486); well-defined whitish tubercles occasionally on anterior half of carapace (KU 40174); white tubercles not surrounded with black ocelli; pattern of white dots seemingly less contrasting in _pallidus_ than in _guadalupensis_, owing to pale brown or tan carapace; small tubercles along anterior edge of carapace equilateral or conical having sharp tips.

Large females usually having pale brown carapaces with slightly contrasting, brownish, mottled and blotched, patterns; white prominences often evident posteriorly and anteriorly in middle of carapace and in nuchal region; tubercles along anterior edge of carapace equilateral or conical in shape.

Pattern on side of head and snout variable and of no diagnostic value; postocular stripe uninterrupted having dark borders (UMMZ 92754), or interrupted having pale segment behind eye (TU 13282); other variations in pattern shown on TU 10170 and 15818; pale stripes on snout having dark inner borders that join and form acute angle (TU 381), or lacking dark inner borders and having uninterrupted dark line connecting anterior margins of orbits (TU 13280); other variations in pattern on snout shown on TU 1232, 1291 and 15819; specimens representing ill.u.s.trations of variation in pattern on snout (Fig. 5 d, e, f) all from same locality, Lewisville, Lafayette County, Arkansas; contrasting pattern on side of head of dark marks on pale background; contrasting pattern of dark marks on dorsal surface of limbs; markings on hind limbs generally larger than those on forelimbs; small or fine markings of some specimens reducing contrast in pattern (TU 478, 488); carapace sometimes having few small blackish dots confined to margin (CNHM 15474, TU 487, 1253, 13266); ventral surface of plastron and soft parts of body whitish and usually lacking dark markings; small blackish marks often occurring on flap of carapace, in region of bridge, or on chin and throat (TU 399, 469, 475, 472, 13281).

Ontogenetic variation in PL/HW, mean PL/HW of specimens having plastral lengths 7.0 centimeters or less, 4.15, and exceeding 7.0 centimeters, 5.32; ontogenetic variation in CL/CW, mean CL/CW of specimens having plastral lengths 8.5 centimeters or less, 1.10, and exceeding 8.5 centimeters, 1.14; mean CL/PCW, 2.12; mean HW/SL, 1.38 (including subspecies _guadalupensis_); mean CL/PL, 1.36.

_Variation._--In 1953, I casually glanced at a hatchling softsh.e.l.l from the Calcasieu River drainage in the private collection of Mr.

Wilfred T. Neill; the specimen was considered by Neill (1951:15) as "... an intergradient one (with the _hartwegi-spinifer_ population in the lower Mississippi drainage)." The hatchling does deviate from "typical" _pallidus_ in having darkish flecks posteriorly on the carapace.

I have seen only one adult male (USNM 94457) from the Sabine River drainage (Orange County, Texas) that shows characteristics of _guadalupensis_ (white dots on carapace encircled with small black ocelli); another adult male (USNM 94456) from the same locality resembles _pallidus_. Those two USNM specimens were mentioned by Neill (1951:13) as indicating intergradation with "... the mixed _spinifera-hartwegi-asper_ populations of Louisiana."

Two adult males (SM 2889, Pl. 40, bottom, left, and TCWC 471, Trinity River drainage) have blackish ocelli surrounding the white dots on the posterior part of the carapace; two large females (TU 14402, Pl. 40, bottom, right, plastral length, 17.5 cm., and TU 14417 plastral length, 21.3 cm., both from the Trinity River) have contrasting mottled and blotched patterns with white dots visible on the carapace.

These turtles show alliance with _guadalupensis_.

Some individuals from the Brazos River drainage have features suggesting those that are characteristic of _guadalupensis_.

Hatchlings may have large white dots on the anterior half of the carapace (USNM 55601). Adult males may have dusky ocelli surrounding the white dots on the carapace (TU 14169, 14559.1, 14559.2). The whitish dots, rarely as large as two millimeters, are never so large as in _guadalupensis_ (three mm. in diameter), and are usually smaller anteriorly than posteriorly; TU 14169 has white dots approximately the same size (1.2 mm.) on the anterior half as on the posterior half of the carapace. The tubercles on adult males are equilateral or subconical, usually having sharp tips (TU 14348, 14559.1, 14559.2); the tubercles on large females are subconical, resembling the end of a bullet, and, in both s.e.xes the tubercles are less conical than those on specimens of _pallidus_ from farther east.

Three specimens from the Brazos River drainage are particularly impressive in their alliance with _guadalupensis_. SM 2556, an adult male, has large white dots that are encircled with black ocelli on the posterior half of the carapace, but lacks white dots on the anterior half. TNHC 14068, a hatchling, has small black dots interspersed with the larger white dots posteriorly. CNHM 46289 has large white spots on the carapace that are surrounded with two to four black dots; scattered black dots also intermix with white spots on the surface of the carapace (less extensive anteriorly).

Color notes taken from a freshly-killed adult male (KU 47121) from the Brazos River, seven miles below Whitney Dam, Bosque-Hill county line, Texas, are: Carapace pale brown or tan bordered by black line, having pale lemon yellow rim; yellowish-cream spots on carapace faintly surrounded with black stippling; dorsal surface of soft parts of body olive having black marks and patches of grayish; webbing on limbs having golden or yellowish hue, brighter distally; interorbital region brown; black-bordered, postocular stripe orange-cream; snout and side of head olive having pale areas of orange-cream; iris cream having black stripe; yellowish at juncture of dark dorsal and pale ventral coloration with orangish tinge on forelimbs and head; tail pale brown or tan, flanked by black borders that suffuse laterally into lemon-yellow; undersurface whitish, pale yellow on neck, bluish-gray on throat.

_Comparisons._--_T. s. pallidus_ most closely resembles _T. s.

guadalupensis_, but can be distinguished from that subspecies in having small white tubercles, rarely two millimeters in diameter, on a pale background, that are not surrounded by blackish ocelli, and are usually absent, or not conspicuous on the anterior third of the carapace in adult males; also there are usually no conspicuous white tubercles or dots on the anterior third of the carapace in hatchlings.

Many adult males of _pallidus_ from the Brazos and some from the Trinity River drainages often have dusky or black ocelli surrounding the white dots posteriorly on the carapace; males from these river systems may be distinguished from _guadalupensis_ in having most, if not all, white dots on the anterior half of the carapace smaller than those posteriorly, and a pale brown carapace (in life, usually darker in _guadalupensis_). _T. s. pallidus_ (and _guadalupensis_) is distinguished from _emoryi_ in lacking a widened pale rim posteriorly, and in having small white spots on the anterior half of the carapace.

_T. s. pallidus_ resembles _guadalupensis_ and _emoryi_ in having white spots on the carapace in adult males. _T. s. pallidus_ differs from _spinifer_, _hartwegi_ and _asper_ in lacking blackish dots or ocelli that occur in the center of the carapace. _T. s. pallidus_ resembles _emoryi_ but differs from _guadalupensis_ in lacking black ocelli surrounding the white spots. _T. s. pallidus_ resembles _spinifer_, _hartwegi_ and _asper_ but differs from _guadalupensis_ and _emoryi_ in having tubercles along the anterior edge of the carapace that are conical having sharp tips in males, and conical in large females.

_T. s. pallidus_ resembles _spinifer_ and _hartwegi_ but differs from the other subspecies in having a narrow head. _T. s. pallidus_ differs from _emoryi_ but resembles the other subspecies in having a wider carapace. _T. s. pallidus_ resembles _emoryi_ and _guadalupensis_, and differs from the other subspecies in having the carapace widest farther posterior than one-half the length of the carapace. The snout of _pallidus_ and _guadalupensis_ is shorter than in _spinifer_ and _hartwegi_, but longer than in _emoryi_. _T. s. pallidus_ differs from _asper_ but resembles the other subspecies in having a relatively long plastron.

_Remarks._--Intergradation of the subspecies _pallidus_ and _guadalupensis_ is of a clinal nature in which populations successively show a gradual resemblance to _guadalupensis_ from western Louisiana and eastern Texas westward to central Texas. Because the sharpest break in this cline of characters occurs between the Colorado and Brazos River drainages, the turtles living in the Brazos River drainage and eastward are referred to _pallidus_, whereas those in the Colorado River drainage and westward are referred to _guadalupensis_. For further comments on intergradation between these two subspecies, see the account of _T. s. guadalupensis_.

Taylor (1935:217-18) reported on some specimens of _Amyda spinifera_ that were obtained by Mr. R. E. McEntyre in "... the spring and summer of 1926, chiefly about Lewisville, Lafayette County (Arkansas)." Of the catalog numbers listed by Taylor from Lewisville, 58 (KU, alcoholic) represent _pallidus_. Three, having the same locality data, have features that are characteristic of _hartwegi_. KU 2944 (one of three specimens having this catalog number) is a female having a pale, mottled and blotched carapace approximately one foot in length; there are remnants of two dark ocelli, and many widely-scattered, well-defined dark spots near the periphery of the carapace. KU 2963 (one of three specimens having this catalog number) is an adult male that has solid, blackish dots on the entire surface of the carapace.

KU 2964 (one of two specimens with this catalog number) is an adult male that has ocelli approximately five millimeters in diameter on the carapace (indistinct in center of carapace).

Lewisville is situated in the drainage basin of the Red River and is approximately eight miles east of the Red River and 30 miles west of the westernmost tributary of the Ouachita River drainage. _T. s.

pallidus_ occurs in the Red River drainage; _hartwegi_ occurs in the Ouachita River drainage. Perhaps there is intergradation between _pallidus_ and _hartwegi_ in the intervening streams. There is no data to indicate from which river or stream each specimen obtained by McEntyre came; one would presume that all specimens came from the Red River drainage. But this is not certain. Certainly the 47 specimens designated herein as _pallidus_ came from the Red River drainage. I suspect that KU 2944, 2963 and 2964 were obtained from tributaries of the Ouachita River drainage.

_T. s. pallidus_ intergrades with the _spinifer-hartwegi_ population where the Red River joins the Mississippi River in the lower Mississippi Valley in Louisiana. The majority of 13 juvenal specimens from the Red River near Shaw, Concordia Parish, Louisiana (USNM 99862-69, 99871-75), resemble _pallidus_ in having inconspicuous white tubercles on a pale brown carapace. The white tubercles are conspicuous in USNM 99871. Some specimens have a few small dark dots confined to the margin of the carapace, as do some "variant"

individuals from well within the geographic range of _pallidus_. USNM 99865 is referred to _hartwegi_ because the carapace is covered with dark ocelli approximately one millimeter in diameter. Some specimens from farther west in the Red River drainage are referred to _hartwegi_. One (USNM 100420) of three from Natchitoches Parish, Louisiana (TU 5763, USNM 100420-21), having blackish dots on the carapace, is applicable to _hartwegi_. Of two turtles from Grant Parish, Louisiana (TU 5647, 12735), only 12735 has dark dots and ocelli (_hartwegi_). One specimen from Rapides Parish, Louisiana (TU 14040), having dark dots on the entire surface of the carapace, is referred to _hartwegi_.

Most specimens from the lower Atchafalaya River drainage are referable to _pallidus_. Eastward, intergradation occurs with the _spinifer-hartwegi_ population; USNM 100089-90 from a.s.sumption Parish, near Napoleonville, Louisiana, are referred to _pallidus_. TU 11983, from Bayou Lafourche, Raceland, La Fourche Parish, and TU 13698.11, from Bayou Gauche in St. Charles Parish, Louisiana, are juvenal males that combine the characteristics of _pallidus_ and _hartwegi_; the carapaces are covered with blackish spots and posteriorly have distinct whitish dots. The population in the Atchafalaya River more closely resembles _pallidus_ than it does _hartwegi_ or _spinifer_. In former times the Atchafalaya River was presumably continuous solely with the Red River (inhabited by _pallidus_). Now, these two rivers and the Mississippi River are interconnected in east-central Louisiana. A large volume of water of the Mississippi drainage is conveyed to the Gulf of Mexico by the Atchafalaya, and someone has said that by approximately 1975, unless man interferes, two-thirds to three-fourths of the total volume of water of the Mississippi River will be drained by the Atchafalaya. One can expect, therefore, an increase in the influence of the _hartwegi-spinifer_ population in the Atchafalaya River drainage.

_Specimens examined._--Total 270, as follows: ARKANSAS: _Lafayette_: KU 2930-37, 2939-40, 2942, 2944 (two of three specimens bear this catalog number), 2945-57, 2958 (2), 2959-61, 2963 (two of three specimens bear this catalog number), 2964 (one of two specimens bears this catalog number), 2965-73, 2987-89, 3056, Lewisville.

LOUISIANA: _Acadia_: USNM 100151-59, Mermentau River. _a.s.sumption_: USNM 100089-90, Bayou Lafourche, "near" Napoleonville. _Beauregard_: TU 1231-32, 1253-55, 1291, 13211, 13266, Sabine River, 8 mi. SW Merryville. _Bienville_: TU 5649-50, Lake Bistineau. _Caddo_: TU 381, 397-99, 469-72, 474-90, 678, 10170, Caddo Lake: TU 15818-19, Cross Lake. _Calcasieu_: UMMZ 92754, 5 mi. W Iowa. _Cameron_: TU 1122, Laca.s.sine Wildlife Refuge. _Concordia_: USNM 99862-64, 99866-69, 99871-75, Red River, "near" Shaw. _De Soto_: SM 2374-75, Wallace Bayou. _Grant_: TU 5647, Lake Iatt. _Iberville_: USNM 83985, 2 mi. E Mounds; USNM 100239-41, Grand Lake west of White Castle; USNM 100380, Plaquemine; USNM 100412, 100414-15, 100419, Spanish Lake, "near" St.

Gabriel. _Jefferson Davis_: Calcasieu River drainage, WTN (no number, see page 524). _Natchitoches_: TU 5763, Bermuda; USNM 100421, "near"

Natchitoches. _Sabine_: TU 13210, 13212-13, 13265, 13280-82, 13303-06, Sabine River, 8 mi. SW Negreet. _St. Martin_: USNM 100160, Bayou Chene; USNM 100650, Atchafalaya. _St. Mary_: USNM 100395-97, 100404, 100409-10, Berwick Bay near Morgan City.

OKLAHOMA: _Atoka_: OU 8966, Rock Creek, 10 mi. E Atoka; OU 8978, McGee Creek, 7 mi. SW Daisy. _Caddo_: ANSP 100, Was.h.i.+ta River, Fort Cobb.

_Choctaw_: OU 27126, Mayhew Creek, 2 mi. NW Boswell. _Comanche_: OU 4130, 4266, 5390, 8333, 12953, 19986, Wichita Mountains Wildlife Refuge. _Jackson_: OU 13012, 6 mi. E El Dorado. _Kiowa_: CNHM 15474.

_Le Flore_: OU 6791, Kiamichi River, 8 mi. W Arkansas State Line.

_McCurtain_: OU 2149-50, 2152, 2155, 17126-28, 17185, 2 mi. SW Smithville; USNM 70397, Red River. _Marshall_: KU 40175-76, 50830-31, 50847, OU 27290, 27297, 27562-63, TU 16076 (5), 16175 (6), 16662 (5), Lake Texoma, 2 mi. E Willis; KU 50832, mouth of Caney Creek, 4 mi. SW Kingston. _Pushmataha_: OU 2151, 2157; OU 11365, Buffalo Creek, 5 mi.

NW Tuskahoma.

TEXAS: _Archer_: TU 16174, 16668-69, Lake Diversion. _Bell_: SM 5667-69, Nolan Creek. _Bosque_: KU 47121, 7 mi. below Whitney Dam, Brazos River. _Brazos_: BCB 4436, 10 mi. E College Station; BCB 4437, 17 mi. S College Station; BCB 4438, 4 mi. N Bryan; KU 50833, 4 mi. W College Station; SM 2556, TCWC 472, Wickson Lake; TCWC 539, Little Brazos River; TCWC 4692, 8 mi. NE Bryan; TCWC 5121, 2 mi. S College Station; TCWC no number. _Clay_: TCWC 7258, 8 mi. NW Ringgold, Montague County; TU 16667.1, 3 mi. W Byers. _Dallas_: MCZ 3987, "near"

Dallas; ANSP 13243, Dallas. _Donley_: ANSP 13440, S of Clarendon.

_Eastland_: KU 3132, Cisco. _Galveston_: TCWC 7251, Alta Loma.

_Harris_: UMMZ 92753, Little Cypress Creek, 1 mi. N Westfield; USNM 94335-36, "near" Houston. _Harrison_: USNM 95386, 16.5 mi. SE Caddo Lake. _Hill_: TU 14169, Richland Creek, 0.7 mi. W Mertens. _Leon_: CNHM 46290, 5 mi. W Marquez; TCWC 8994, 8996, 6 mi. NW Normangee.

_Liberty_: TU 14402, 14417, Trinity River, "near" jct. with Big Creek.

_McLennan_: BCB 4665-66, 6 mi. NNE McGregor; SM no number, 2037, 2452, 2552, 2558, 2560, 2640, 5263, 6533, Lake Waco; SM 0185, Middle Bosque River; SM 2104, 6732, Upper Bosque River; SM 5072, Bull Hide Creek; UI 2399, 1.5 mi. W China Springs; UMMZ 64063, Waco; USNM 55601.

_Madison_: TCWC 471, 517, Twin Lakes. _Montgomery_: TCWC 540, 3 mi. S Conroe. _Nacogdoches_: TNHC 14112, Legg Creek, 5 mi. S Dougla.s.s.

_Orange_: UMMZ 117060, 3 mi. S Orange; USNM 94456-57, Orange.

_Randall_: TTC 576, Palo Duro Canyon, 15 mi. SE Canyon. _Shackelford_: TU 14547, Clear Fork Brazos River, Fort Griffin State Park.

_Somervell_: TCWC 8995, TU 14559 (4), Brazos River, 5-6 mi. E Glen Rose. _Trinity_: SM 2889, Groveton. _Walker_: TNHC 20829, 5 mi. E New Waverly. _Waller_: TNHC 14068, 2.7 mi. E Brazos River on US 90.

_Williamson_: MCZ 1627 (2); TU 14348, San Gabriel River, 6.5 mi. E Georgetown. _County unknown_: ANSP 13448, Wichita River; USNM 7640, Brazos River.

_Records in the literature._--LOUISIANA: _Cameron_: Sabine Refuge (Cagle and Chaney, 1950:386).

OKLAHOMA: _Le Flore_: 6 mi. W Page. _McCurtain_: 14 mi. SE Broken Bow (Trowbridge, 1937:301).

TEXAS: _Bosque_: Bosque River, "near" Valley Mills (Strecker, 1928:6).

_Harris_: Add.i.c.ks (Brown, 1950:250). _Henderson_: Cedar Creek (Strecker, 1926a:7). _Jefferson_: 12 mi. SW Port Arthur (Guidry, 1953:56). _Liberty_: Daisetta (Brown, _loc. cit._); San Jacinto River (Strecker, 1915:15). _McLennan_: "near" Crawford (Brown, _loc. cit._).

_Orange_: 1 mi. N Bridge City (Guidry, _loc. cit._). _Tarrant_: Trinity River, Fort Worth (Stejneger, 1944:66). _Taylor_: Abilene (KKA). _Tyler_: Colmisneil (Siebenrock, 1909:603). _Walker_: 6 mi. E Huntsville (TCWC 329, listed in card file). _Wheeler_: 5 mi. N Wheeler (Brown, _loc cit._).

=Trionyx ater= Webb and Legler

Black Softsh.e.l.l

_Trionyx ater_ Webb and Legler, Univ. Kansas Sci. Bull., 40:21, pls. 1 and 2, 1960, April 20.

_Type._--Holotype, KU 46903, alcoholic female; obtained 16 km. S Cuatro Cienegas, Coahuila, Mexico, by John M. Legler (and party), September 6, 1958.

_Range._--Basin of Cuatro Cienegas, central Coahuila, Mexico (see map, Fig. 22).

_Diagnosis._--Posterior margin of carapace of some females having fine corrugations, edge often ragged, and no pale outer margin; septal ridges reduced in adult males; over-all dorsal coloration (in preservative) dark, lacking contrasting patterns.

_Description._--Plastral length of adult male, 9.6 centimeters (KU 46911); of largest female, 18.4 centimeters (KU 46903).

Adult male: anterior edge of carapace smooth; septal ridges reduced; pale outer rim, and small, whitish, dots posteriorly on carapace; surface of carapace slightly gritty or sandpapery posteriorly; snout broadened; over-all dorsal coloration dark gray or slate; contrasting pattern on soft parts of body lacking; ventral surface whitish having few blackish marks posteriorly on undersurface of carapace.

Females: posterior margin of carapace usually having fine corrugations; edge of carapace posteriorly often ragged; pale rim of carapace absent; mottled and blotched pattern not contrasting on blackish carapace; dorsal surface of soft parts of body dark gray or slate, lacking contrasting pattern; ventral surface of carapace and posterior part of plastron usually having many blackish flecks and markings; tubercles lacking on anterior edge and in center of carapace posteriorly; septal ridges well developed.

Medial angle of epiplastron (as observed through overlying skin) bent at angle of approximately 90 degrees. Other osteological characters presumably as in _spinifer_.

Range in length of plastron (cm.) of 11 females (mean follows extremes); 10.8-18.4, 15.0; proportional measurements of 12 specimens (including adult male, mean follows extremes): PL/HW, 4.70-5.43, 4.93; CL/CW, 1.28-1.43, 1.32; CL/PCW, 1.98-2.42, 2.15; HW/SL, 1.22-1.58, 1.37; CL/PL, 1.29-1.44, 1.36; some females (especially KU 46908) have noticeably elongate carapaces.