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Title: Description of a New Softshell Turtle From the Southeastern United States
Author: Webb, Robert G.
Language: English
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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

BY

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

BY

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.

     Head extended to level of eyes; head terminating in long,
     rounded, flexible snout; nostrils rounded with no ridges
     projecting from nasal septum; jaws closed, each covered by
     fleshy lips except anteriorly where horny portions of jaws
     are exposed; iris with dark stripe through pupil.

     Forefeet and hind feet well-webbed and with five digits
     each; each limb with nails on first three digits; dorsal
     surface of each forelimb with four cornified areas, three of
     which have a free edge; each hind limb with two cornified
     areas, one smooth on posterodorsal surface and other with
     free edge on posteroventral surface.

     Tail terminating in flexible point and not extending beyond
     posterior edge of carapace; anus to tip of tail, 2.6 mm;
     anus to posterior edge of carapace, 8.1 mm.

     In preservative: Ground color of carapace dark tan having
     pattern of 49 brownish spots; 47 spots circular; two spots
     noticeably elongate, one representing fusion of two circular
     spots; 17 spots on carapace not exceeding 2.0 mm in
     diameter, whereas 32 spots range from 2.5 to 4.0 mm in
     diameter; periphery of carapace pale except anteriorly;
     maximum width of pale margin (posteriorly), 3.3 mm; junction
     of pale margin and dorsal ground color formed by rough-edged
     line composed of small, closely-set dots; pattern of fine
     punctations and other marks on dorsal surface of forelimbs
     and hind limbs.

     Ground color of underparts whitish, lacking markings; top of
     head and snout gray, lacking markings; lower eyelids with
     small dark dots.

     _Description of paratypes._--Adult females (2 specimens). No
     striping on dorsal surface of snout; pale postocular stripe
     not distinct, dark borders obscure (head not extended in TU
     13473); carapace circular, pale brown with mottled pattern;
     carapace lacking pattern of large spots; dark marks present
     in pale margin of carapace; dorsal surface of soft parts of
     body finely stippled, larger marks on hind limbs and on
     anterior surface of forelimbs near their insertions;
     plastron and ventral surface of soft parts of body without
     markings. Maximal measurements, respectively, are: length of
     plastron, 172 and 180 mm; length of carapace, 238 and 263
     mm; width of carapace, 203 and 218 mm; width of head, 28
     and? mm.

     Immature female (1 specimen). Carapace circular having
     juvenal pattern of large spots, some of which have borders
     darker than their centers and are best described as ocelli;
     junction of pale margin and ground color of carapace formed
     by ill-defined, ragged dark border; dorsal surface of
     forelimbs and hind limbs finely streaked and dotted, larger
     marks occurring toward insertions of forelimbs; lower border
     of pale postocular stripe in contact with upper margin of
     postlabial pale stripe; no stripes on dorsal surface of
     snout; fine markings on dorsal surface of neck. Maximal
     measurements are: length of plastron, 56 mm; length of
     carapace, 82 mm; width of carapace, 77 mm; depth of shell,
     13 mm; width of head, 12 mm.

     Adult males (3 specimens). No striping on dorsal surface of
     snout; pale postocular stripe with thick, black borders
     immediately behind eye; width of black borders equal to
     approximately one-half width of pale postocular stripe;
     dorsal surface of soft parts of body with indistinct
     markings that are larger on hind limbs; plastron and ventral
     surface of soft parts of body without markings; small dark
     spots posteriorly along ventral edge of carapace; pale
     margin of carapace lacking markings or having few small
     black spots; carapace circular with or without pattern of
     large spots. Maximal measurements of smallest and largest
     specimens, respectively, are: length of plastron, 108 and
     118 mm; length of carapace, 160 and 177 mm; width of
     carapace, 142 and 152 mm; width of head, 21 mm.

     Hatchlings (14 specimens). These paratypes resemble the
     holotype in all features mentioned; markings on neck tend to
     form longitudinal streaks in TU 17303 and 17304. There are
     no secondary sexual differences in hatchling turtles.

     There is some variation in hatchling turtles. Four from the
     Escambia River have dorsal spots 3 mm or larger in greatest
     diameter and on three specimens the dorsal spots number 27,
     37 and 37 (total number not discernable in TU 16682); none
     of the dorsal spots is ocellate. Maximal measurements of
     these three hatchlings, respectively, are: length of
     plastron, 35, 36 and 37 mm; length of carapace, 50, 50 and
     52 mm; width of carapace, 44, 45 and 47 mm; depth of shell,
     11 mm; width of head, 9 mm. Nine hatchlings from the Pearl
     River at Varnado have more (all small) dorsal spots, which
     may be ocellate. The dorsal spots and ocelli do not exceed 2
     mm in their greatest diameter except that some of those of
     TU 17304 are 3 mm; the spots range in number from 38 (TU
     17303) to 63 (TU 17304). Maximal measurements of the
     smallest and largest specimens, holotype excepted, are:
     length of plastron, 30 and 33 mm; length of carapace, 42
     and 46 mm; width of carapace, 37 and 43 mm; depth of shell,
     9 and 10 mm; width of head, 9 and 10 mm. The holotype
     resembles hatchlings from the Escambia River in having
     large, non-ocellate dorsal spots 3 mm in greatest diameter,
     and larger measurements.

     One other specimen (not designated as a paratype),
     consisting of a head with a few attached cervical vertebrae,
     was obtained on a sand bank of the Escambia River, Florida.
     The postocular stripe, bright yellow with black borders, was
     especially vivid in this adult male (KU 47116).

[Illustration: FIG. 1. Map of southeastern United States showing record
stations of _Trionyx muticus calvatus_ (solid symbols) and _Trionyx m.
muticus_ (open symbols). Circles indicate specimens examined; triangles
indicate records in the literature. The question mark refers to a
specimen bearing catalogue number 17236 in the collection of Tulane
University (see comments on page 524 concerning No. 17236 from the
Amite River).]

     _Range._--_Trionyx m. calvatus_ is known from the Pearl,
     Pascagoula and Escambia river drainages and is to be
     expected in the Tombigbee-Alabama river drainage (Fig. 1).
     Tinkle (1958:41, fig. 53, stippled) has indicated the
     probable range of _calvatus_. This subspecies is unknown
     from the Mississippi and Tennessee river drainages, which
     are inhabited by _T. m. muticus_. The western limit of
     distribution is the Pearl River drainage and probably those
     streams of the Florida Parishes of Louisiana that drain into
     Lake Ponchartrain. The most easterly record of occurrence
     for _T. m. calvatus_ is in the Escambia River drainage; the
     eastern extent of geographic range is not known.

     I have seen three preserved young turtles having the
     characteristic spotted pattern from the Pascagoula drainage
     in eastern Mississippi. These specimens are uncatalogued and
     in the collections at Mississippi Southern College,
     Hattiesburg, Mississippi.

     There is a specimen of _T. m. muticus_ labeled as from
     Mobile, Alabama (MCZ 1596), for which I believe the locality
     datum is incorrect. It is a young turtle having a
     well-defined pattern on the carapace and is without doubt a
     representative of _T. m. muticus_. Mobile is in the large
     drainage basin, of the Tombigbee, Black Warrior, Coosa and
     Alabama rivers, which is between the Escambia and Pearl
     rivers.

     Yarrow (1882:28) reported a specimen of _Amyda mutica_, USNM
     11630, from Gainesville, Florida. This record was questioned
     by Cahn (1937:179), and has been disregarded by subsequent
     authors. Stejneger (1944:23) lists this specimen number with
     uncertainty from Mt. Carmel, Illinois. The exact geographic
     provenance of this specimen is seemingly unknown.

     _Habitat._--I have collected eggs of _T. m. calvatus_ on
     sand banks of the Escambia River, Florida. The Escambia
     River has a sand-gravel bottom, extensive sandy banks, a
     moderately-rapid current, and is flanked by a thick riparian
     forest. It is approximately 80 feet wide with fallen trees
     and brush intermittently emergent along the shoreline. The
     sand bar-habitat along the Pearl River has been mentioned by
     Anderson (1958:212). All records thus far are from lotic
     habitats.

     _Comparisons._--_Trionyx m. calvatus_ is most closely
     related to _Trionyx m. muticus_. Both subspecies have the
     following characteristics: (1) no enlarged tubercles on the
     anterior edge of the carapace, (2) no ridge projecting from
     the nasal septum, and (3) a smooth carapace in adult males.
     These characters distinguish these two subspecies from the
     several subspecies of _T. spinifer_, and, except for the
     smooth carapace in adult males, from _T. ferox_. Another
     feature of _T. m. calvatus_ and _T. m. muticus_, not known
     to be definitive or diagnostic but noticed on occasion, is
     the pale orange cast, in life, of the dorsal surface of the
     carapace and soft parts of the body in young of these
     turtles.

     The spotted pattern of juveniles of _calvatus_ is easily
     distinguished from the pattern of _muticus_ (small dots,
     streaks and dashes) figured by Agassiz (1857, vol. 2, pt. 3,
     pl. 6, fig. 6), Smith (1950:154, fig. 104), Conant
     (1938:192, pl. 21, fig. 1; 1958, pl. 11, opposite p. 94),
     and Cahn (1937:177, pl. 24C).

     Unfortunately, the distinctive dorsal spotting in young
     _calvatus_ becomes obscure or absent in some adults of both
     sexes. Spotting in large males is not so well-defined as in
     juveniles; it may be absent (TU 17306.3), or indicated by
     two obscure spots (KU 17117), but is usually evident, at
     least posteriorly. The spotted pattern is absent in large
     females, which have a pale, mottled and blotched pattern of
     lichen-like figures; dorsal spots are obscure in TU 17305
     (length of plastron, 56 mm).

     Two additional features are, so far as known, universal in
     _calvatus_; these are: (1) the absence of striping on the
     dorsal surface of the snout, and (2) the presence of thick,
     black borders of the postocular stripe in adult males. These
     features have also been observed in some specimens of
     _muticus_; their presence in _muticus_ cannot be properly
     evaluated at this time, and is seemingly not due to
     individual variation. These two characters, however, coupled
     with the distinctive juvenile pattern of spots, serve, in
     combination, to distinguish _calvatus_ from _muticus_.

_Discussion._--The two populations are recognized as subspecies
because: (1) there is close resemblance, (2) the diagnostic characters
pertaining to pattern are few and superficial, and (3) the geographic
ranges are allopatric, but juxtaposed. It is probable that _muticus_
and _calvatus_ would be capable of interbreeding if they were not
spatially isolated. It should be pointed out, however, that there is no
evidence of intergradation between _muticus_ and _calvatus_ in the
lower Mississippi Valley as has been reported for the subspecies of _T.
spinifer_ (Conant and Goin, 1948), and that the degree of difference
between _calvatus_ and _muticus_ is greater than that between some
subspecies of _T. spinifer_.

     _Specimens examined._--All the localities listed below are
     plotted on the distribution map (Fig. 1). Only those
     specimens of _T. muticus muticus_ are listed that serve to
     delimit the range of _T. m. calvatus_. Fortunately, the
     identification of the specimens of _muticus_ is certain as
     all show the characteristic juvenile pattern, except the
     large female, TU 7543, from southeastern Louisiana. USNM
     95133-34 (carapaces and plastrons only) and TU 17236 are
     females, which lack the diagnostic spotted pattern of
     _calvatus_; the former are referred to this subspecies on
     geographic grounds (Pearl River at Columbia, Mississippi).
     TU 17236, from the Amite River, is dubiously relegated to
     _calvatus_ on the supposition that this river and others in
     the Lake Ponchartrain drainage will yield the characteristic
     juveniles.

     _Trionyx m. calvatus_ (33 specimens): TU 13473, 16682,
     17301, 17302-.1, KU 47116 (skull only), Escambia River, 2
     miles east, 1 mile north Century, Escambia Co., Florida; TU
     17303-.4, 17304-.3, Pearl River, Varnado, Washington Par.,
     Louisiana; TU 17306-.3, Pearl River, 9 miles south
     Monticello, Lawrence Co., Mississippi; TU 16956, KU
     47117-19, USNM 7655, Pearl River, vicinity of Monticello,
     Lawrence Co., Mississippi; TU 17236?, Amite River, near
     Baton Rouge, Louisiana; TU 13795, Bogue Chitto River, Enon,
     Washington Par., Louisiana; TU 17305, no data, Louisiana;
     USNM 95133-34, Pearl River, Columbia, Marion Co.,
     Mississippi; UI 31071, Pearl River, 14 miles northeast
     Jackson, Rankin Co., Mississippi; Uncatalogued, see page
     523, Leaf River, 3 miles southeast New Augusta, Perry Co.,
     Mississippi.

     _Trionyx m. muticus_ (6 specimens): TU 5989, Ouachita River,
     Monroe, Ouachita Par., Louisiana; TU 7543, Vacherie, St.
     James Par., Louisiana; CNHM 7845, Gayles, Caddo Par.,
     Louisiana; USNM 92605, Greenville, Washington Co.,
     Mississippi; USNM 113228, Jonesville, Catahoula Par.,
     Louisiana; USNM 118167, Wheeler Reservoir, Tennessee River,
     Alabama.

     _=Records in the Literature.=_--USNM 113228, referred to
     above as _Trionyx m. muticus_ is listed by Stejneger
     (1944:56) as _Amyda s. spinifera_; four of the specimens
     listed above (USNM 7655, 92605, 95133-34) are recorded by
     Stejneger (_op. cit._:23-34) as _Amyda mutica_. Cook
     (1946:185) records seven specimens of the _muticus_ group
     from Mississippi as follows: 1, no data; 1, Vicksburg,
     Warren Co.; 3, Forrest Co.; 1, Crawford Bridge, Jones Co.;
     1, Lake Park, Columbus, Lowndes Co. I have not seen these
     specimens; they are plotted on the distribution map--the
     one from Vicksburg as _muticus_ and the others as _calvatus_
     on geographic grounds. The hatchlings of _Trionyx muticus_
     referred to by Anderson (_loc. cit._) include the nine
     paratypes from Varnado, Louisiana.

[Illustration: PLATE 13

_Trionyx muticus calvatus_ new subspecies, hatchling, UI 31071,
holotype (× 1.3). Top, dorsal view. Bottom, ventral view, Photographs
by John M. Legler.]

[Illustration: PLATE 14

_Trionyx muticus calvatus_ new subspecies, hatchling male, TU 17301,
paratype (× 1.3). Top, dorsal view. Bottom, lateral view of left side.
Photographs by Isabelle Hunt Conant.]


LITERATURE CITED

ANDERSON, P. K.

     1958. The photic responses and water-approach behavior of
     hatchling turtles. Copeia, 1958, 3:211-215, 5 figs., August
     28.

AGASSIZ, L.

     1857. Contributions to the natural history of the United
     States. Vol. II, Part III. Embryology of the turtle. Little,
     Brown and Co., Boston, pp. 451-643, 27 pls.

CAHN, A.

     1937. The turtles of Illinois. Illinois Biol. Monogr.,
     16(1-2):1-218, 31 pls., 15 figs., 20 maps, August 31.

CONANT, R.

     1938. The reptiles of Ohio. Amer. Midl. Nat., 20(1):1-200,
     26 pls., 38 maps, July.

     1958. A field guide to reptiles and amphibians of eastern
     North America. Houghton Mifflin Co., Boston, pp. vii+366, 40
     pls., 62 figs., 248 maps.

CONANT, R., and C. J. GOIN.

     1948. A new subspecies of soft-shelled turtle from the
     central United States, with comments on the application of
     the name _Amyda_. Occas. Pap. Mus. Zool., Univ. Michigan,
     510:1-19, 2 pls., 1 map, June 15.

COOK, F. A.

     1946. Distribution of species of Amyda in Mississippi.
     Journ. Mississippi Acad. Sci., 1941-1947:185-190.

SMITH, H. M.

     1950. Handbook of amphibians and reptiles of Kansas. Univ.
     Kansas Mus. Nat. Hist., Misc. Publ., 2:1-336, 233 figs.,
     September 12.

STEJNEGER, L.

     1944. Notes on the American soft-shell turtles with special
     reference to _Amyda Agassizii_. Bull. Mus. Comp. Zool.,
     94(1):1-75, 30 pls.

TINKLE, D. W.

     1958. The systematics and ecology of the _Sternothaerus
     carinatus_ complex (Testudinata, Chelydridae). Tulane Stud.
     Zool., 6(1):1-56, 57 figs.

YARROW, H. C.

     1882. Check list of North American Reptilia and Batrachia,
     with catalogue of specimens in the U. S. National Museum.
     Bull. U. S. Nat. Mus., 24:1-249.


_Transmitted April 30, 1959._


27-8360



       *       *       *       *       *

Transcriber's Notes

Italicized text is shown within _underscores_.

Bold text is shown within =equal signs=.

Repositioned the map and plates between paragraphs.





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