1. Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA. bmwynd@vt.edu
2. Instituto Museo de Ciencias Naturales, Universidad Nacional de San Juan, Av. España 400 (norte), J5400DNQ San Juan, Argentina. martinez@unsj.edu.ar; ccolombi@unsj.edu.ar; oalcober@unsj.edu.ar