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UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY

Volume 11, No. 9, pp. 517-525, 2 pls., 1 fig. August 14, 1959

Description of a New Softshell Turtle From the Southeastern United States

ROBERT G. WEBB

UNIVERSITY OF KANSAS LAWRENCE 1959

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Robert W. Wilson

Volume 11, No. 9, pp. 517-525, 2 pls., 1 Fig. Published August 14, 1959

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED IN THE STATE PRINTING PLANT TOPEKA, KANSAS 1959

27-8360

Description of a New Softshell Turtle From the Southeastern United States

ROBERT G. WEBB

Examination of softshell turtles allied to Trionyx muticus from the southeastern United States discloses the presence of an undescribed subspecies inhabiting river systems of the Gulf Coast.

The author is indebted to Mr. Roger Conant for constructive criticism of the manuscript. I am grateful also to many fellow students for assistance in field work or for other courtesies, especially William E. Brode, Franklin Sogandares-Bernal, Ernest A. Liner, Donald W. Tinkle, Paul K. Anderson, and John K. Greer. The photographs were provided through the cooperation of Roger and Isabelle Hunt Conant and John M. Legler.

Collections from which specimens were obtained are as follows: TU (Tulane University), USNM (United States National Museum), MCZ (Museum of Comparative Zoology, Harvard College), CNHM (Chicago Natural History Museum), KU (Museum of Natural History, University of Kansas), UI (Museum of Natural History, University of Illinois).

Measurements (in millimeters) were made with a Vernier caliper and a metal tape; those of the holotype were made to the nearest one-tenth millimeter. Plastral length was measured from the posterior edge of the plastron to the anteriormost edge of the ventral surface; other measurements were maximal. Depth of shell was taken only on hatchlings and an immature female. Hatchlings were arbitrarily designated as specimens having plastrons shorter than 44 mm; sex of all specimens except adult males was determined by dissection unless otherwise noted.

=Trionyx muticus calvatus= new subspecies

Gulf Coast Smooth Softshell

Amyda mutica (in part), Stejneger, Bull. Mus. Comp. Zool., 94(1):23-24, 1944.

Amyda muticus (in part), Cook, Jour. Mississippi Acad. Sci., 1941-1947, p. 185, 1946.

Trionyx muticus Anderson, Copeia, 3:211, August 28, 1958.

Holotype.--UI 31071, hatchling, sex undetermined, from the Pearl River, Roses Bluff, 14 miles northeast Jackson, Rankin County, Mississippi; obtained by William F. Childers on August 25, 1952 (Plate 1).

Paratypes.--A total of 20 alcoholic specimens: TU 17301, hatchling male (Plate 2). TU 17302-.1, 16682, three hatchling females, and TU 13473, adult female, from the Escambia River, 2 miles east and 1 mile north of Century, Escambia County, Florida; TU 17306, adult female, from the Pearl River, 9 miles south of Monticello, Lawrence County, Mississippi; USNM 7655, hatchling, sex undetermined, and KU 47117-19, three adult males, from the Pearl River, 1 mile south to 4 miles north of Monticello, Lawrence County, Mississippi; TU 17303-.4, 17304-.3, five hatchling males and four hatchling females, from the Pearl River, Varnado, Washington Parish, Louisiana; TU 17305, immature female, no data.

Diagnosis and definition.--A subspecies of softshell turtle most closely allied to Trionyx muticus muticus but differing from that subspecies in having: (1) a juvenal pattern of large, circular spots, (2) no stripes on dorsal surface of snout, and (3) postocular stripe with thick, black borders immediately behind eye in adult males. T. m. calvatus resembles T. m. muticus, and differs from the several subspecies of Trionyx spinifer in having: (1) no enlarged tubercles on anterior edge of carapace, (2) no ridge projecting from nasal septum, and (3) a smooth dorsal surface on carapace in adult males. T. m. calvatus and T. m. muticus resemble T. ferox in having a smooth dorsal surface on carapace in adult males, but differ from T. ferox in having: (1) no tubercles along anterior edge of carapace, and (2) no ridge projecting from nasal septum.

Description of holotype.--Carapace circular, widest at region of bridge; margin entire; dorsal surface smooth; anterior margin of carapace lacking tubercles; blunt vertebral ridge evident anteriorly; maximum length, 53.1 mm; greatest width, 46.3 mm; greatest depth, 11.5 mm.

Plastron small, extending slightly farther forward than carapace; anterior lobe truncate with slight midventral indentation; posterior lobe rounded, sides forming acute angle; certain features of bony elements of plastron visible through overlying skin; width of bony bridge, 4.5 mm; maximum length of plastron, 37.5 mm.