Yucatan Peninsula (México) is a geologically late topographic feature on Mexico´s landscape, but one that contains important faunal complexes, both modern and fossil. Those appearing during the Pleistocene are starting to provide an overall picture of just what that landscape looked like. Both dry and wet deposits have been studied, with data providing a highly diverse fauna containing at least 11 orders, 28 families, 54 genera, and 70 species. Dry caves, like Loltún Cave, have provided a very diverse faunal complex with many small and medium size animals, while wet deposits, like underwater caves, are rich in larger mammal remains, including megafauna. Hoyo Negro is a pit within an underwater cave, and is one of the richer deposits with megafauna, containing at least 12 species of extinct and extant mammals. Extinct species include the highland gomphothere (Cuvieronius tropicalis), three species of ground sloth (Nothrotheriops shastensis, a new megalonychid taxon, and a mylodontid), and sabertooth cat (Smilodon cf. fatalis). Modern species include tapir (Tapirus), peccary (Tayassu), and extralimital records like bobcat (Lynx rufus) and coyote (Canis latrans). A tremarctine bear (Arctotherium) also occurs in the assemblage and represents a range extension of this South American taxon. The fauna includes both Neotropical taxa (sloths, gomphotheres), taxa with Nearctic affinities (carnivores, lagomorphs) and probably some endemic animals, like the megalonychid sloth and tremarctine bear. The presence of bobcat and coyote, and the occurrence of the Shasta ground sloth, indicate a drier and cooler climate in the region during the terminal Pleistocene.