Although similar in physical characteristics, dune ecosystems of the Namibian and North American Deserts have distinctive geological ages, regional climates and microenvironments. Specialist sand-diving lizards have evolved in each system albeit at different tempos and modes of speciation. Meroles anchietae (Lacertidae), and Gerrhosaurus skoogi (Gerrhosauridae) of the Namib Desert, and six taxa of Uma (Phrynosomatidae) inhabiting isolated dune systems across the North American Deserts have separately evolved convergent external morphologies, but differ in body mass, reproductive cycles, number and size of progeny, metabolic physiology and behavior. All are omnivores consuming variable proportions of vegetation including seeds along with insects that are part of detritus-based food webs. Populations of M. anchietae and Uma undergo dramatic density changes depending on annual surpluses or deficits of energy and water, mediated through unpredictable rainfall and prey availability. Unlike Namib lizards, which inhabit large contiguous dune landscapes, several species of Uma are seriously threatened by habitat loss and fragmentation from development and recreational activities. Harsh conditions common to all desert dune environments present similar challenges to species that live there, but differences in their age, climate and geographic extent offer exceptional opportunities for understanding evolution and ecosystem structure and function. Keywords: Adaptations to harsh Environments, Detritus-based food webs, Gerrhosaurus skoogi, Lizard ecology, Meroles anchietae, Sand dune ecology, Uma spp.