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قراءة كتاب Description of a New Softshell Turtle from the Southeastern United States

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Description of a New Softshell Turtle from the Southeastern United States

Description of a New Softshell Turtle from the Southeastern United States

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دار النشر: Project Gutenberg
الصفحة رقم: 5

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

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