The first evidence of iguanians and scincoids from the lower Eocene of the Cos locality (Phosphorites du Quercy, France)

Abstract Squamate faunas from the lower Eocene of Europe are rare. We here describe pleurodontan iguanian (potentially Geiseltaliellus Kuhn, 1944), scincoid, and Squamata indet. jaw remains from Cos locality (near the Caylus village, southwestern France). The age of the Cos deposit has been proposed to fit the MP 10−11 interval (MP 10b; late Ypresian). Thus, it either corresponds to the end of the Early Eocene Climatic Optimum (EECO) or slightly postdates it. Although very fragmentary, the finds represent the first evidence of these clades in this locality, which is one of the oldest from Phosphorites du Quercy, adding to the squamate paleobiodiversity of the site. Besides iguanians and scincoids, the fauna also includes gekkotans, glyptosaurids, varanoids, and a constrictor snake. Some of the genera from Cos are known solely from this locality, revealing a crucial part of the squamate history in Europe. In the last few years, our knowledge of the Paleocene and especially early Eocene lizard faunas has increased. This allows a better understanding of the faunas and their changes due to temperature changes and migrations. Records are still very sketchy at European localities, but the overall picture is somewhat clearer, even on a smaller scale. A small but visible drop in lizard diversity appears to be present at localities from MP 8−9 relative to those from MP 7, whereas at MP 10, the diversity slightly increased. This appears to correlate well with observed changes in temperature.