Illinois Natural History Survey - University of Illinois

Dichotomous (branching) keys are often used to identify species. At each point, the user chooses between two choices to get to the next point, eventually eliminating all other choices and identifying the species. 

The keys below are adapted from those in the Field Guide to Amphibians and Reptiles of Illinois and the Field Manual of Illinois Mammals. To purchase copies of these (and other) field guides, visit our publications section.

Key to Frogs and Toads of Illinois

Key to Salamanders of Illinois

Key to Snakes of Illinois

Key to Turtles of Illinois

Key to Lizards of Illinois

Key to Skulls of Illinois Mammals