Turtles that have a relatively small adult size are the African aquatic sideneck turtle, the painted turtle, mud turtles, musk turtles and the Central American wood turtle. None of these turtles exceed 9 inches in length when they are adults.
The U.S. Food and Drug Administration passed legislation in 1975 that banned the sale of pet turtles that have a shell length that is 4 inches or smaller. This was done to reduce the amount of U.S. salmonella cases related to turtles. It has been proven that turtles can carry salmonella and that small turtles are more likely to be handled by small children, increasing the chances of children contracting the disease.