A Probable Neoceratopsian Manus Track from the Nanushuk Formation (Albian, Northern Alaska)

Abstract

We report a likely neoceratopsian manus track from an exposure of the Nanushuk Formation along the Colville River in northern Alaska. The track described here contains the impressions of five digits, arranged as an arc, which identify this specimen as a manus. Details of the impression suggest that it is neoceratopsian rather than ankylosaurian. The length of the chord of the arc of the track is approximately 25 cm, which is half the size of manus tracks found west of Denver, Colorado, USA attributed to the 10 m long Maastrichtian Triceratops.The Nanushuk Formation is a succession of complexly intertonguing marine and nonmarine strata interpreted as shelf, deltaic, strandplain, fluvial, and alluvial overbank deposits. Deposited in the foreland basin north of the Brooks Range, the rock unit is present throughout most of the northern foothills belt and subsurface of the central and western North Slope coastal plain. Fossil and radiometric data place this outcrop within the Albian. If the identification of this track is correct, this is one of the earliest occurrences of neoceratopsians from North America. The occurrence of this track in Alaska substantiates the biogeographic model of faunal exchange between Asia and North America through a Cretaceous land bridge known as Beringia.

New Dinosaur Ichnological, Sedimentological, and Geochemical Data from a Cretaceous High-Latitude Terrestrial Greenhouse Ecosystem, Nanushuk Formation, North Slope, Alaska

“…Finally, tectonic reconstructions suggest that the formation of the land bridge connection between Asia and North America occurred by the Albian [94] and was used by neoceratopsians at this time [11]. The track diversity shown in this study demonstrates some level of more advanced ecological complexity by vertebrates regarding niche separation and resource use just a few million years later.…”

“…Additional three-toed tracks in the Nanushuk Fm. have been photographed and presented as sedimentologic oddities elsewhere in the literature [21], while a four-toed track attributed to a neoceratopsian has also been reported from this rock unit [11]. Though the record of fossil bones from the Nanushuk Formation is far from robust, the dinosaur bones found thus far can be attributed to members of the Ornithopoda [52].…”

“…The Albian-Cenomanian time was the earliest episode of faunal exchange between Beringia and Asia, e.g., [11]. This route between the North American and Asian continents has repeatedly been key to the dispersal of organisms starting during the time represented by the Nanushuk Formation up to the more recent Pleistocene faunal exchanges.…”

Beauty or brains? The braincase ofPachyrhinosaurus perotorumand its utility for species-level distinction in the centrosaurine ceratopsidPachyrhinosaurus

“…Whereas the region now known as Alaska has been considered the gateway for faunal communication between Asia and North America (Russell 1993; Sereno 2000; Fiorillo 2008a; Zanno 2010; Fiorillo & Adams 2012), and this gateway was probably established at least 108 Ma (Fiorillo et al . 2010b), the Prince Creek Formation records this exchange in the greatest detail.…”

“…The fossil localities in this rock unit are compelling because not only are they at high latitudes today, but given the rotation of specific tectonic plates and the assembling of eastern Asia and northwestern North America, the Prince Creek Formation was deposited at latitudes similar to, or higher than the current geographic position (Witte et al 1987;Lawver et al 2002). Whereas the region now known as Alaska has been considered the gateway for faunal communication between Asia and North America (Russell 1993;Sereno 2000;Fiorillo 2008a;Zanno 2010;Fiorillo & Adams 2012), and this gateway was probably established at least 108 Ma (Fiorillo et al 2010b), the Prince Creek Formation records this exchange in the greatest detail.…”