Cretaceous Mammals from Montana

Abstract

A series of Cretaceous mammal faunas, beginning with standard late Cretaceous faunas and continuing with three of Paleocene aspect, are summarized. Four families (Eucosmodontidae, Taeniolabididae, Leptictidae, Arctocyonidae) and one order (Condylarthra) of Tertiary mammals are extended into the Cretaceous. New genera Cimexomys, Stygimys, Procerberus, and Protungulatum are described, as is a small species of Catopsalis. The skeleton of a multituberculate is restored and multituberculate classification is revised.

Mammalian distal humerus fossils from eastern Montana, USA with implications for the Cretaceous-Paleogene mass extinction and the adaptive radiation of placentals

“…We acknowledge the challenges of using isolated and fragmentary postcranial elements for this purpose: (i) taxonomic attributions are inherently tentative; (ii) locomotor inferences are blind to conflicting functional signals across elements (e.g., Chen and Wilson, 2015;Fabre et al, 2015); and (iii) the ability to discriminate among functionally similar locomotor modes (e.g., fossorial vs. semi-aquatic modes) let alone locomotor sub-modes (e.g., different methods of burrowing; Hopkins and Davis, 2009;Chen and Wilson, 2015;Fabre et al, 2015) is weaker than in analyses of more complete skeletons. However, the postcranial record of Late Cretaceous and early Paleogene mammals mostly consists of isolated and fragmentary elements (e.g., Deischl, 1964;Sloan and Van Valen, 1965;Szalay and Decker, 1974;Clemens, 2002;DeBey and Wilson, 2014); thus, we emphasize that the discussion points presented above, which follow from the results of our analyses of the limited postcranial fossil data (DeBey and ; this study), should be considered working hypotheses to be more robustly tested in future studies with better samples. To this end, we urge researchers to redouble their efforts to amass larger samples of KPg postcranial fossils by revisiting existing museum collections and investing in more intensive field efforts, particularly in undersampled depositional environments that might preserve more complete, associated postcranial remains of mammals (Wilson and Varricchio, 2014).…”

“…As such, the rationale is unclear for why so many specimens that resemble EuC were attributed to ?Protungulatum rather than some combination of these five archaic ungulate species (Rigby, 1981). It might point to identification bias that stemmed from one or more factors: (1) Protungulatum was the first genus of archaic ungulate named from the early Puercan (Sloan and Van Valen, 1965), whereas Mimatuta and Oxyprimus were named over a decade later (Van Valen, 1978); (2) many institutions contain older collections from Pu1 assemblages in which specimens were attributed to Protungulatum, and (3) Protungulatum, on the basis of dental material, was the most abundant of these three taxa (Wilson, 2004). Until a humerus is found in association with dental specimens of one of these five taxa, we recommend that isolated humeri referable to the EuC morphotype be attributed to archaic ungulate indet.…”

“…Others have commonly referred specimens matching this morphotype to Procerberus, perhaps because (i) Procerberus sp. was the first "insectivoran" named from the study area (Sloan and Van Valen, 1965); (ii) humeri specimens were attributed to this taxon in museum collections and the attributions were propagated by subsequent researchers; and (iii) Procerberus, on the basis of dental evidence, was the most abundant mammal in Pu1 assemblages . Nevertheless, given the multiple candidate taxa for this morphotype and the lack of associated skeletal and dental material of Procerberus (Rigby, 1981), we do not assign EuD to a particular taxon.…”

“…Research to date on K-Pg mammalian postcrania has mostly focused on a narrow taxonomic scope (i.e., multituberculates, plesiadapiform primates; Deischl, 1964;Krause and Jenkins, 1983;Szalay, 1994;Borths and Hunter, 2008;Chester et al, 2015) or on a single assemblage (e.g., the Bug Creek Anthills; Deischl, 1964;Sloan and Van Valen, 1965;Szalay and Decker, 1975). More temporally and taxonomically comprehensive research has been limited by low sample sizes of postcranial fossils, which is likely a function of the rarity of these elements (and extreme rarity of skeletons) relative to the thousands of mammalian teeth known from these deposits (e.g., Sloan and Van Valen, 1965;Archibald, 1982;Lofgren, 1995;Clemens, 2002;DeBey and Wilson, 2014;.…”

“…More temporally and taxonomically comprehensive research has been limited by low sample sizes of postcranial fossils, which is likely a function of the rarity of these elements (and extreme rarity of skeletons) relative to the thousands of mammalian teeth known from these deposits (e.g., Sloan and Van Valen, 1965;Archibald, 1982;Lofgren, 1995;Clemens, 2002;DeBey and Wilson, 2014;. Despite small sample sizes, our recent study of fossil femora from eastern Montana (DeBey and Wilson, 2014) shows that isolated postcranial elements provide patterns of change in taxonomic richness, body size, and locomotor ecology across the K-Pg boundary that supplement patterns from dental data (Wilson, 2013.…”