Dryolestids are known from the Jurassic through
Early Cretaceous of the Northern Hemisphere (North America, Eurasia, and North Africa) and from the
Late Cretaceous through to the
Miocene of South America. The oldest named member of Dryolestidae is
Anthracolestes from the Middle
Jurassic (
Bathonian) aged
Itat Formation in western Siberia. Fragmentary remains attributable to dryolestidans are known from the equivalently aged
Forest Marble Formation of England and the
Anoual Formation of Morocco. The youngests fossils of Dryolestidans in the Northern Hemisphere are the dryolestids
Crusafontia cuencana from
Uña and the
Camarillas Formation, Spain and
Minutolestes submersus and
Beckumia sinemeckelia from
Balve, Germany, which all date to the
Barremian-
Aptian stages of the Early Cretaceous, though a fragmentary lower molar from the late Cretaceous
Mesaverde Formation in Wyoming has been tentatively attributed to Dryolestidae. In South America, by contrast,
Meridiolestida thrived in the Late Cretaceous, diversifying in a myriad of forms such as the saber-toothed
Cronopio and the herbivorous
mesungulatids, becoming some of the most ecologically diverse Mesozoic South American mammals.
Groebertherium from the Late Cretaceous of South America has a more primitive morphology similar to Northern Hemisphere dryolestids and may be more closely related to the North Hemisphere dryloestidans than to Meridiolestida. With the advent of the Cenozoic, dryolestoids declined drastically in diversity, with only the large dog-sized herbivore
Peligrotherium being known from the
Palaeocene. The exact reasons for this decline are not clear; most likely they simply did not recover from the
K-Pg event. Nonetheless, meridiolestidans would continue to survive until the
Miocene, from when
Necrolestes is known; a gap of 50 million years exists between it and
Peligrotherium. A tooth fragment, now lost, found in the Eocene aged
La Meseta Formation of the
Antarctic peninsula, is possibly a meridiolestidan. == Taxonomy ==