Main sources: Stebbins, Robert, 1985, A Field Guide to Western Reptiles and Amphibians, Houghton Mifflin; Behler, John & Wayne King, 1979, The Audubon Society Field Guide to North American Reptiles and Amphibians, NY: Alfred Knopf.
Yellow Mud Turtle (Kinosternon flavescens) (?)
This small turtle (below) was seen in lower Sierra Blanca Canyon Wash after a Monsoon flooding event. We're saying Yellow Mud Turtle, though we didn't examine it more closely than the videocam image shown here.(Click on the image to enlarge it.)
Stebbins says that a feature distinguishing the Yellow from its relative the Sonoran Mud Turtle (K. sonoriense) is a "9th marginal shield higher than it is wide" -- in the cited work, see plate 17 and description, and p. 98-99). The image above when examined in closeup shows relevant marginal shields that appear to be higher than wide -- the 9th marginal shield is the one just above the hind leg, which is just visible at dead center bottom of the enlargement. Mainly stream- or pond-dwelling (including intermittent streams), the Yellow Mud Turtle does not occur much north of the southern tip of central or eastern Arizona (see map 62 in Stebbins), while the Sonoran species is widespread in our area right up to the lower edge of the Mogollon Rim (map 61).
Western (Desert) Box Turtle (Terrapene ornata)
This full-grown Box Turtle, below, was seen near the San Pedro River at Charlie and Jeannine Thomas's place August 30, 1998. Box Turtles are so-called because one of these turtles can completely enclose itself within its shell (as can be seen in the image below left). The shell is high, rounded, and typically marked with radiating lines as shown more clearly here on the right. The characteristic lines here are faded with age as well as blurred by the movement of the videocamera, from which these stills are derived. This one moved along quite fast, once prodded. (Click on each image for an enlargement.)
Box Turtles are primarily prairie turtles, no doubt attracted to the native grasses Charlie and Jeannine have been growing on their land near the San Pedro River. They also eat insects, berries and other fruits, young shoots, and leaves.
Here, below, is a much smaller and younger one (the length of the writing pen is 5" [13 cm]), which has just emerged from the earth near the Teran Wash confluence with the San Pedro River on July 19, 2004, after the rains of July 14-16 -- on the left image you can clearly see fresh mud still sticking to the top front of its carapace, though it is a good distance from any mud. This one covered considerable distance, moving more than 100 yards in the course of a morning's exploration. According to Stebbins (p. 103), this one is a female, since the spots on the forelegs are yellowish -- they are reddish on the males (click on each image to enlarge it):...
Below, this Box Turtle, encountered in Lower Hot Springs Canyon in August 2005, began retreating into the box as we approached it closely; at right, this must have been close to maximal retreat: (click on each image to enlarge it):...
Spiny Softshell (Trionyx spiniferus)
We saw one of these in the Hot Springs Stream, in November of 1988, when Saguaro Juniper Corporation was just hatching. I (RNH) had never seen one, or heard of it, before (and have never seen one again in the San Pedro River drainage), so it was unforgettable. It was a little larger than the size of a man's hand. Since we lacked a camera, we derive the image below from a drawing in Stebbins, Plate 18.
The defining characteristics of the Spiny Softshell are its extreme flatness, with a flexible, pancakelike shell (covered with leathery skin rather than horny shields) and a pointed snout. They can reach 18" in length. The one we saw was practically invisible because its back was covered with algae, and indeed one of us half stepped on it while wading along the edge of the stream, which was running strongly at the time. Stebbins's distribution map shows the Texas subspecies as occupying the upper part of the Gila River drainage, and also the Lower Colorado River. Probably they were formerly present in the Lower Gila River as well, before habitat loss due to overdevelopment.
Spiny Softshells live mainly in permanent water, though they are agile both in water and on land. They eat earthworms, snails, fish, frogs, tadpoles, and occasionally aquatic plants.