Porthidium dunni (Hartweg and Oliver, 1938). Dunn’s Hognosed Pitviper is a “priority two species” that has been assessed Environmental Vulnerability Score of 16 (see the following article). This pitviper is found primarily at low elevations along the foothills of the Sierra Madre del Sur physiographic region and the coastal plain of the Planicie Costera del Pacífico and Planicie Costera de Tehuantepec physiographic regions (Mata-Silva et al., 2015b) in southern Oaxaca and extreme western Chiapas, Mexico. This individual was found ca. 3.6 km NNW of La Soledad, Municipio de Villa de Tututepec de Melchor Ocampo, Oaxaca. ' © Vicente Mata-Silva 543 www.mesoamericanherpetology.com www.eaglemountainpublishing.com The endemic herpetofauna of Mexico: organisms of global significance in severe peril JERRY D. JOHNSON1, LARRY DAVID WILSON2, VICENTE MATA-SILVA1, ELÍ GARCÍA-PADILLA3, AND DOMINIC L. DESANTIS1 1Department of Biological Sciences, The University of Texas at El Paso, El Paso, Texas 79968-0500, United States. E-mail:
[email protected], and
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[email protected] 2Centro Zamorano de Biodiversidad, Escuela Agrícola Panamericana Zamorano, Departamento de Francisco Morazán, Honduras. E-mail:
[email protected] 3Oaxaca de Juárez, Oaxaca 68023, Mexico. E-mail:
[email protected] ABSTRACT: Life on Earth exists due to the interactions among the atmosphere, hydrosphere, and litho- sphere. Humans, however, have created and are faced with the consequences of an interrelated set of problems that impact all of these spheres, including the biosphere. The decline in the diversity of life is a problem of global dimensions resulting from a sixth mass extinction episode created by humans.