Kyphosis and other Variations in Soft-shelled Turtles

Excerpt

Kyphotic (hump-backed) soft-shelled turtles have been known for many years in Asia and America. Gressitt (Peking Natural History Bulletin, 2 (pt. 4): 413-415, figs. 1-5, 1937) has reviewed accounts of such turtles, and recorded the anomaly in Amyda sinensis (Wiegmann) and A. steindachneri (Siebenrock) of Asia and in unidentified species in the United States. Records of kyphosis in American species apparently are few.

Three skeletons in the University of Kansas Museum of Natural History demonstrate occurrence of the condition in at least 3 American species: Amyda emoryi (Agassiz), A. mutica (Le Sueur) and A. spinifera (Le Sueur). The specimen of A. emoryi (Catalog No. 2219) was taken at Phoenix, Maricopa Co., Arizona, by Victor H. Householder, on May 1, 1926. The second specimen, called to my attention by C. W. Hibbard, was taken in 1936 from the Kansas River at Lawrence, Douglas Co., Kansas, by Max Wheatley, to whom I am indebted for the accompanying photographs and permission to describe the specimen which he has added to the Museum's collections (No. 23230). The identity of No. 23230 is established as A. mutica by the absence of spines (see fig. 3) and by a number of cranial characters. The specimen of A. spinifera (No. 23026) is without locality data; its identification is verified by the presence of spines on the front of the carapace.

In the specimen of A. mutica (see figures) the hump forms a smooth, high curve, closely resembling the condition in Gressitt's specimens of A. steindachneri (op. cit.: fig. 1). In the other two the hump is lower and its apex forms a relatively sharp angle; in the specimen of A. spinifera the posterior face of the hump is more nearly vertical than the anterior face. In A. emoryi the rear edge of the apex is sharply inclined (at an angle of about 45°), whereas the remainder of the surface slants at an angle of about 35°.

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....