Kyphosis and other Variations in Soft-shelled TurtlesSmith, Hobart M. (Hobart Muir)
Science
Kyphosis and other Variations in Soft-shelled Turtles
Smith, Hobart M. (Hobart Muir)
Turtles
In the accompanying table of measurements of specimens in the University
of Kansas Museum of Natural History the height is measured from the end
of the rib opposite the highest elevation to the crest of the elevation,
by projected lines. The length is measured from the anterior border of
the nuchal plate to the posterior edge of the last costal plate. The
width is measured from tip to tip of the longest ribs. Catalogue
numbers of the specimens, with indication of the localities of capture
are as follows: Nos. 2215-9, 2803, 2824, 2837, Phoenix, Maricopa Co.,
Arizona; Nos. 19459-60, Ozark, Franklin Co., Arkansas; Nos. 2225-9,
Lewisville, Lafayette Co., Arkansas; Nos. 1867-70, 1874-6, 1879, 1881,
1930-1, 2666, 2761-2, 2826, 2838-42, Devalls Bluff, Prairie Co.,
Arkansas; No. 16528, Orange Co., Florida; Nos. 1872, 1878, 1943, 1964,
Doniphan Lake, Doniphan Co., Kansas; No. 2220, Douglas Co., Kansas; No.
23230, Kansas River, Douglas Co., Kansas; No. 18159, Harper Co., Kansas;
No. 2757, Smoky Hill River, Trego Co., Kansas; No. 23026, no data.
The three abnormal specimens vary in width/height ratio from 1.83 to
3.14. In the 37 normal turtles measured, the corresponding ratio is 4.64
to 7.85. The ratio of 4.64 is possibly subject to correction since the
shell tends to warp in some specimens, especially in those retaining the
skin about the periphery of the shell. The warping does not produce a
marked convexity in transverse section, but does so in longitudinal
section. Accordingly the height as here measured is little effected, and
the comparison with width rather than length of shell provides for the
lesser error from warping. There appears to be no close correlation of
proportions with either size or sex.
It is of interest that _Amyda ferox_ is the most distinctive in
proportions of the carapace. Its carapace is longer in relation to its
width than that of any of the other species. The average relative length
of the carapace of _A. emoryi_ is intermediate between that of _A.
ferox_ and the averages of _A. spinifera_ and _A. mutica_, but the
overlap in range with the latter two is complete.
The cause for kyphotic anomalies is unknown. That it is accompanied by a
greater degree of growth in the vertebral column than in the periphery
of the costal plates is obvious. There seems to be no well-established
accommodation for the difference in growth, since the hump produced by
it varies considerably in form.
There is no trend from small to large specimens in size of the hump;
large and small humps occur in both large and small specimens.
Accordingly it seems that the humped condition is developed in the late
embryo or early post-embryonic life, and does not later change.
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