Cagle's map turtle has intricate patterns on the carapace and plastron, as well as serrated edges on the posterior of the carapace, as is typical of all map turtles. It is smaller than most map turtles, and very sexually dimorphic, with males reaching only 4 in (10 cm) carapace length while females can exceed 7 in (18 cm) in carapace length.
Conant R. 1975. A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition. Boston: Houghton Mifflin. xviii + 429 pp. + 48 plates. ISBN 0-395-19979-4 (hardback), ISBN 0-395-19977-8 (paperback). (Graptemys caglei, p. 58 + Figure 9 on p. 56 + Map 21).
Haynes D, McKown RR. 1974. A New Species of Map Turtle (Genus Graptemys) from the Guadalupe River System in Texas. Tulane Studies in Zoology and Botany18 (4): 143-152. ("Graptemys caglei new species").