Introduction

Paleoenvironmental reconstruction is an objective of paleoecology, and biological proxies have been traditionally used to infer ancient environments. Stenotopic taxa have been considered the best proxies. Some recent studies showed the importance of certain key physiological processes in adapting to changing environmental conditions or new habitats; this calls attention to review the traditional conceptions about classical interpretations of proxies. Mexico is a megadiverse country with a great and complex geological history. The most studied groups in the Mexican fossil record are the invertebrates, and in descending order, vertebrates, microfossils, and plants. Some of the better-studied taxa are Quaternary in age, so a large part of paleoenvironmental reconstructions has focused on this period, but the fossil record of other periods has been significantly improved in the last decade, thus allowing it to be used in the paleoenvironmental reconstruction of Mexican localities.