Summary: LATE CRETACEOUS MAMMALIAN FAUNA FROM THE HELL CREEK
FORMATION, SOUTHEASTERN MONTANA
Yue Zhang and J. David Archibald, Department of Biology, San Diego State University,
San Diego, California 92181-4614, U.S.A.
The richest known Late Cretaceous mammalian fauna from the Hell Creek Formation
was discovered in southeastern Montana in the 1980's. Although a faunal list was
included in a paleobiogeographic study, the taxa have never been described. This study
describes and compares this important fauna to other Late Cretaceous mammalian faunas.
There are some 20 mammal producing localities, but the richest are the four localities
composing Claw Butte Anthills local fauna and the single richest locality composing the
Spigot-Bottle local fauna. Over 1000 mammal specimens have been recovered by screen
washed from an in situ channel fill composed of silty sand. The Hell Creek Formation is
quite thick in this area, reaching 150m, with the two local faunas ranging from 65 to 61 m
below the formational contact. Based on faunal content the two local faunas are not
different. Spigot-Bottle local fauna includes the multituberculates Mesodma formosa, M.
hensleighi, M. thompsoni, Cimolodon nitidus, Cimolomys gracilis, Meniscoessus
robustus; the metatherians Protalphadon lulli, Alphadon marshi, A. wilsoni, Pediomys
cooki, P. elegans, P. florencae, P. hatcheri, P. krejcii, Turgidodon rhaister, Didelphodon
vorax; and the eutherians, Batodon tenuis, Cimolestes incisus, C. propalaeoryctes, C.
stirtoni, Gypsonictops sp., cf. Paranyctoides sp. In addition, from the Claw Butte local