Multituberculate and other mammal hair recovered from Palaeogene excreta.

Evidence of hair from several extinct mammals has been recovered from a rich accumulation of fossil excrement from the Late Palaeocene beds of Inner Mongolia, China. This highly unusual and previously undocumented depositional occurrence consists of hundreds of mammalian carnivore coprolites (fossil faeces) and a lesser number of probably raptorial bird regurgitalites (fossil pellets). The fossil hair occurs as impressions and natural casts in the extremely fine-grained, calcareous matrix that cements the skeletal remains within these faecal structures and preserves even the cuticular scale pattern on individual hair. Hair from at least four mammalian taxa, most notably the multituberculate Lambdopsalis bulla, has been identified. This record constitutes the first tangible evidence that, along with monotremes and therian mammals, multituberculates were hirsuite, and lends support for the presence of this mammalian feature in the most recent common ancestor of these three groups.