Zhelestidae

The earliest zhelestid remains occur in the Cenomanian of Central Asia. By the Campanian, however, they are present in Europe and North America, and by the Maastrichtian in India and in Madagascar (UA 8699). In Europe, then an island continent, taxa usually accepted to be zhelestids are the most common Late Cretaceous mammal remains, aside from Hateg Island where kogaionid multituberculates are more common instead, though there is a single possible zhelestid tooth there as well.[7]

Zhelestids are well specialised towards an herbivorous diet, their teeth suited for a lateral chewing mechanism similar to that of modern ungulates. An exception to this might be forms like Oxlestes and Khuduklestes, which are normally interpreted as carnivorous, and perhaps a few forms like Borisodon which may have been insectivorous. Ranging from mouse sized forms to ones comparable to small ungulates in size, zhelestids occupied a massive variety of ecological guilds.

In contrast to their dietary divergence, the few available limb remains suggest that they weren't very specialised locomotion wise, in contrast to some other basal eutherians like for instance Zalambdalestes, which was long-limbed and had several adaptations for cursoriality and hopping.

There is evidence that zhelestids were in direct competition with another clade of Mesozoic herbivorous mammals, the multituberculates, being rarer in places where these were most common and vice versa.[8] However, multituberculates eventually outlived zhelestids, surviving the KT-mass extinctions everywhere but Asia, where the niches taken by both clades in the Cretaceous would be taken by early rodents.[9]