Climatic change from the late Eocene to early Oligocene is marked by a moderate decrease in global temperature and, in central North America at least, drying. To improve understanding of how reptile groups responded, a 37-million-year old (late Eocene) assemblage of lizards and amphisbaenians (worm-lizards) from North Dakota is described. Nineteen species are identified, although most are not well-enough preserved to warrant formal names; fourteen of these are previously unknown. These species include the last-known North American records of Acrodonta (agamas, mastigure lizards, and chamaeleons), Diploglossinae (galliwasps), and Varanidae (monitor lizards). The iguanians in particular are remarkable for their higher-level taxonomic diversity and include an early member of a group that today is almost exclusively found in South America. Although the fossil record is now compatible with a decrease in species diversity in response to this climatic change, many sampling biases remain, which must be overcome in order to truly understand the response of the reptilian fauna.