Jerry MacDonald as an amateur fossil collector who in the late 1980s dicovered well-preserved and abundant Early Permian vertebrate tracks. The tracksites are located in the Robledo Mountains, west of Las Cruces, New Mexico, USA, preserved in redbed supratidal to intertidal sequences that contain the aforementioned vertebrate trackways (made by amphibians, synapsids, and small reptiles), as well as invertebrate trackways, interpreted as those of scorpions, centipedes, millipedes, horseshoe crabs, and other arthropods.