North American Recent Soft-Shelled Turtles (Family Trionychidae)Webb, Robert G. (Robert Gravem)
Science
North American Recent Soft-Shelled Turtles (Family Trionychidae)
Webb, Robert G. (Robert Gravem)
Soft-shelled turtles
Blackish marginal rings on carapace number two, three or four
posteriorly, but decrease in number anteriorly; segments of marginal
rings may extend to nuchal region; marginal rings increasingly
interrupted inwardly; pattern of hatchlings having well-defined
marginal rings that are not extensively interrupted (often males), or
having marginal rings broken into small segments or series of dots,
and pale outer margin of carapace marked by ill-defined, hazy, inner
border (often females); conspicuous marginal rings often lacking on
hatchling females; pale rim of carapace not four or five times wider
posteriorly than laterally; carapace having blackish dots, spots,
small ocelli or a combination thereof; marks on carapace of slightly
varying sizes, some occasionally barlike (usually males); some
hatchling females showing pale, irregular blotching on carapace, often
characterized by small lichenlike figures superimposed on blackish
dots.
Striping on snout variable; pale, dark-bordered stripes usually unite
in front of eyes and form right or acute angle; medial dark borders of
pale stripes on snout not joined anteriorly, broken into segments or
dots, reduced to single median line, united to form straight line
connecting anterior margins of orbits (usually with slight medial
indentation), or absent; pale postocular and postlabial stripes often
joined, relationship variable and on either side of head; side of head
with or without dark markings, sometimes a pale subocular blotch
bordered below by a dark line; pattern on dorsal portions of soft
parts of body contrasting, less so on limbs of hatchlings; pattern of
irregular dark marks, dark streaks usually coincident with digits;
longitudinal streaks often occur on neck; elongate tail of adult males
usually having well-defined, dorsolateral, pale bands with dark lower
border more diffuse than upper border.
Underparts whitish often with dusky markings on rear of carapace or in
region of bridge; blackish marks often on webbing and portions of
soles and palms, and chin and throat.
Small conical tubercles along anterior edge of carapace on adult
males; remnants of juvenal pattern usually present on carapace of
large females; conical or knoblike tubercles on anterior edge of
carapace of large females; accessory knoblike tubercles in nuchal
region (a paravertebral pair usually most prominent), and posteriorly
in middle of carapace on large females.
Ontogenetic variation in PL/HW, mean PL/HW of specimens having
plastral lengths 7.0 centimeters or less, 3.87, and exceeding 7.0
centimeters, 4.94; ontogenetic variation in CL/CW, mean CL/CW of
specimens having plastral lengths 8.5 centimeters or less, 1.11, and
exceeding 8.5 centimeters, 1.16; mean CL/PCW, 1.71; mean CL/PL, 1.45.
_Variation._--The sex of some hatchlings can be distinguished by the
pattern on the carapace (see Plate 37 for different patterns), but the
sex of many hatchlings cannot be distinguished on the basis of
pattern.
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