A full understanding of change in squamate assemblage composition during the Tertiary is frustrated by sampling problems. It is very difficult even to assess the biases that currently affect the squamate record, much less to correct for them. Nevertheless, the squamates of the Medicine Pole Hills l.f. provide a great deal of new information on the character of late Eocene assemblages. Fourteen previously unreported species are identified in this Chadronian fauna, including an acrodont iguanian, seven iguanids, a scincoid, a new anguimorph, a ?xenosaurid, a varanid, a diploglossine, and Helodermoides; another five are likely already known from that time (see Table 1). Of particular interest are the relatives of early Eocene immigrants from the Old World (Tinosaurus, Saniwa*), a phrynosomatine (fence lizards and relatives), a polychrotine (anoles and relatives), and the last record of the stem-clade of Diploglossinae (galliwasps) in central North America. Three of the new species are named formally. The polychrotine, apparently a member of the Polychrus stem-clade, indicates that the transformation of squamate assemblages was not simply a gradual increase in the richness of iguanid taxa that are currently present in central North America (Phrynosomatinae, Crotaphytinae). Rather, some iguanids, like their counterparts in other parts of the squamate tree, may have had long histories in the area. This conclusion is completely consistent with the explicit recognition that Iguanidae has a great deal of intraclade variability in autecological preference. The fossil record now suggests that squamates in central North America, like those in Europe, suffered a drop in richness in response to Eocene/Oligocene climatic deterioration, but because of remaining sampling problems this observation must be treated with some circumspection. Sampling-standardized studies on new and existing collections are indicated.