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Dinosaur tracks from Cretaceous of Alaska



From: Ben Creisler
bcreisler@gmail.com

A new online paper:


Anthony R. Fiorillo, Thomas L. Adams & Yoshitsugu Kobayashi (2012)
Cretaceous Research (advance online publication)
http://dx.doi.org/10.1016/j.cretres.2012.04.013
http://www.sciencedirect.com/science/article/pii/S0195667112000869



An unnamed nonmarine sedimentary package of rocks in southeastern
Alaska in Wrangell-St. Elias National Park and Preserve has provided
the first evidence of dinosaurs for this vast region. The rock unit is
contained within the Wrangellia Terrane and exposures are of limited
geographic extent. The rock unit is considered to be latest Cretaceous
age. Sections are overwhelmingly dominated by extraformational
conglomerates. Fine- to medium-grained light coloured sandstones are
common and medium grey shales occur as minor components of the
sections. Megafloral specimens indicate an abundance of horsetails,
ferns and gymnosperm wood. Rather than two-dimensional impressions,
most ferns are preserved in three dimensions, suggesting rapid burial.
The abundance of charcoal in these rocks suggests that this area
during deposition was also prone to ecological disturbance. Field
parties found evidence of a small theropod and ornithopods. A single
theropod pes impression is approximately 9 cm long and 7 cm wide.
Attribution to the Theropoda was based on the sinusoidal shape of the
impression of the middle digit. An ornithopod impression, identified
by clearly blunt and rounded digit impressions, is approximately 22 cm
long and 26 cm wide. All impressions are under tracks.