[1] Univ Chile, Fac Med, Programa Fisiol & Biofis, Santiago 7, Chile
[2] Univ Nacl Salta, CONICET, IBIGEO Inst Bio & Geociencias NOA, RA-4400 Salta, Argentina
[3] Amer Museum Nat Hist, Div Vertebrate Zool Herpetol, New York, NY 10024 USA
[4] San Diego State Univ, Dept Biol, San Diego, CA 92187 USA
[5] Univ Nacl San Juan, Fac Ciencias Exactas Fis & Nat, CICEOBIO CONICET Ctr Invest Geosfera & Biosfera, Buenos Aires, DF, Argentina