Clarification of the taxonomic relationship of the extant and extinct ovibovids, Ovibos, Praeovibos, Euceratherium and Bootherium Paula F. Campos a, * , Andrei Sher b,1 , Jim I. Mead c , Alexei Tikhonov d , Michael Buckley e , Matthew Collins e , Eske Willerslev a , M. Thomas P. Gilbert a a Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Østervoldgade 5-7, DK 1350 Copenhagen, Denmark b Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, 33 Leninsky Prospect, Moscow 119071, Russia c Department of Geosciences, Neogene Vertebrate Paleontology Laboratory, and Center for Excellence in Paleontology, East Tennessee State University, Johnson City, TN 37614, USA d Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, St. Petersburg 199034, Russia e BioArCh, University of York, Heslington, York YO10 5DD, UK article info Article history: Received 25 January 2009 Received in revised form 3 May 2010 Accepted 7 May 2010 abstract During the late Pleistocene, a large number of species colonized North America from Eurasia through the Bering Land Bridge. At least four different genera within the tribe Ovibovini are known from this time, the holarctically distributed Ovibos moschatus (the extant musk ox) and Praeovibos, and the nearctically distributed Bootherium and Euceratherium. Questions about the taxonomic relationships of the four North American musk oxen arose soon after their description and continue to be unresolved at the present. In this study we present the first DNA and protein analyses, of the four mentioned genera. Phylogenetic analysis at the mitochondrial level indicates that Praeovibos falls within the diversity of modern Ovibos, which might indicate that Praeovibos is simply an earlier morphotype of the extant species O. moschatus. In contrast Euceratherium and Bootherium are clearly distinct genera, in agreement with the findings of previous morphological studies. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction A number of mammalian megafaunal species crossed from Eurasia into North America during the late Pleistocene through the Bering Isthmus. One such species is the modern musk ox (Ovibos moschatus; Bovidae, Caprinae, Ovibovini). Although represented by a single taxon today, various genera of extinct musk oxen are reported from Pleistocene deposits in North America including Ovibos, Praeovibos and Soergelia (with their Holarctic distribution), Bootherium and Euceratherium (with their endemic Nearctic distribution), and Symbos, which some authors believe is synony- mous to Bootherium (McDonald and Ray, 1989). Euceratherium (shrub ox), is the oldest ovibovid from the Americas, with evidence of its presence there during the early Irvingtonian Land Mammal Age (around 1.1 Mya, Kurtén and Anderson, 1980; this record from California is now in question, personal communication to Mead from Lyn Murray). Late Pleisto- cene (Rancholabrean Land Mammal Age) shrub ox remains have been found from northern California to central Mexico (Fig. 1). Plant remains recovered from dried dung suggests that members of the species were browsers, and preferred hilly to mountainous land- scapes (Kropf et al., 2007). Radiocarbon dates taken on Eucer- atherium dung pellets from the Colorado Plateau indicate extinction as late as 11,500C 14 ybp (Mead and Agenbroad, 1992; Kropf et al., 2007). Thus given that at Burnet Cave, New Mexico, bones of this genus were found in association with human artefacts (Kurtén and Anderson, 1980), it is plausible that they represented a prey species for the first Native American peoples. The second endemic genus to the Americas, Bootherium (helmeted musk ox), was the dominant and most widespread musk ox of the Western Hemisphere roaming from Alaska to Texas, and from the Pacific coast to the Atlantic continental shelf (McDonald and Ray, 1989). It is commonly accepted that Bootherium evolved in broad, intermontane valleys in eastern Beringia, having dispersed to lower plains during the coldest periods of the Illinoian (possibly 200,000 or more years ago) and Wisconsinan (about 90,000e10,000 years ago) glaciations. Habitat preferences of Bootherium are unclear, although fossils representative of the species have been recovered from a variety of grasslands, alpine meadows and woodland sites, suggesting it was adapted to less severe climates than O. moschatus. Questions about the relationship between Symbos and Bootherium arose soon after their description * Corresponding author. Tel.: þ45 35321210; fax: þ45 35321300. E-mail address: paulafcampos@hotmail.com (P.F. Campos). 1 Deceased. Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev 0277-3791/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2010.05.006 Quaternary Science Reviews 29 (2010) 2123e2130