Mexican mud turtle
Kinosternon integrum has an oval carapace (to 20.2 cm) which gradually slopes posteriorly and is depressed over the vertebrals. It may be tricarinate in juveniles, but lack keels or has only a faintly marked medial keel on the posterior vertebrals in adults. The cervical is very narrow. The 1st vertebral is broader than long (wide anteriorly, but narrower posteriorly), touching the first two pairs of marginals; vertebrals 2-4 are longer than broad; and the 5th is also broader than long, but broader posteriorly than anteriorly. Lateral marginals are downturned, but those posterior are flared; the 10th is highest, the 11th next highest. The carapace is gray to yellow brown or dark brown; lighter individuals may have some dark spotting. The double-hinged plastron is large, and may completely, or almost completely, close the shell. It is usually notched posteriorly. The plastral formula is: abd > an > gul > hum > fem > pect; the interanal seam is greater than 67% of the length of the posterior plastral lobe. On the wide bridge, the large inguinal usually touches (often barely) the smaller axillary. Plastron and bridge are yellow with dark seams. The head is large with a protruding snout and hooked jaws. Its rostral shield is pointed anteriorly and wide posteriorly. There are two large barbels on the chin followed posteriorly by two to four pairs of smaller barbels. The head is dark brown dorsally and lighter gray or yellow brown laterally and ventrally. Some dark mottling may occur on the sides of the head, and the yellow jaws may have narrow dark streaks or speckles. The neck is dark brown or gray dorsally, but yellow to pinkish with dark speckles on the sides and bottom. Limbs are gray brown with cream-colored sockets. There are no vinculae. Body skin is relatively smooth, lacking the raised tubercles found in other species.
The karyotype has 56 chromosomes (Bickham and Carr, 1983).
Males are larger (to 20.2 cm) than females (to 18.8 cm) and have long, thick tails terminating in a horny spine. Females have short, spineless tails.
The Mexican mud turtle ranges from southern Sonora and extreme southwestern Chihuahua southward along the Pacific drainages to central Oaxaca, on the central plateau from central Durango and southern Nuevo Leon southward to central Oaxaca, and in the east it occurs in southwestern Tamaulipas.
No subspecies are currently recognized, but it is strongly possible that some populations will prove to be subspecifically distinct.
Kinosternon integrum prefers low-gradient streams with deep pools, at altitudes to 3000 m, but may also be found in roadside ponds and ditches. Hardy and McDiarmid (1969) often found them crossing roads at night.
Courtship and nesting have not been described. The elongated (30 x 16 mm) eggs have white, brittle shells. Hardy and McDiarmid (1969) found hatchlings in Sinaloa in late July, August, and September; and Ewert (1979) reported the average carapace length of 14 hatchlings was 27 mm.
Kinosternon integrum is closely related to K. scorpioides, but Berry (1978a) found no evidence of intergradation or introgression between the two in Mexico. They are not sympatric, but come within 40 km of each other in the Rio Pánuco and Rio Papaloapan drainages. K. integrum is also often confused with K. hirtipes, but males of the latter species have the roughened scaly vinculae on their thighs and crura.
IUCN Red List Status (1996)