R.W. McDiarmid K.A. Nichols P.C. Ustach R. Altig 1998 A key in a different format is presented for the tadpoles of the United States and Canada. More details of ontogenetic variation are included than in many keys and more attention is paid to identifying species by using characteristics of living tadpoles. application/pdf en A key to the anuran tadpoles of the United States and Canada article