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New Pachyrhinosaurus bonebed in Alberta, Canada



Ben Creisler
bcreisler@gmail.com

A new online paper:

Federico Fanti, Philip John Currie & Michael E. Burns (2015)
Taphonomy, age, and paleoecological implication of a new
Pachyrhinosaurus (Dinosauria: Ceratopsidae) bonebed from the Upper
Cretaceous (Campanian) Wapiti Formation of Alberta, Canada.
Canadian Journal of Earth Sciences (advance online publication)
doi: 10.1139/cjes-2014-0197
http://www.nrcresearchpress.com/doi/abs/10.1139/cjes-2014-0197?src=recsys#.VQ9eJfnF_To


The Grande Prairie region (Alberta, Canada) includes some of the
richest Cretaceous fossil sites in North America, including the
recently described bonebed of Pachyrhinosaurus lakustai at the
Pipestone Creek locality. Here we describe a new multi-taxa,
ceratopsian-dominated bonebed from the region, integrating taphonomic,
radioisotopic and paleoecological data. The bonebed can be traced for
107 m and has been excavated over an area of 40 m2 with an average
bone density is 30-50 elements/m2. The new bonebed occurs within Unit
4 of the upper Campanian Wapiti Formation, and 40Ar/39Ar dating
provides an age of 71.89±0.14 Ma, thus making the site equivalent in
age to the upper Drumheller Member of the lower Horseshoe Canyon
Formation of central Alberta. About 88% of vertebrate remains are
ceratopsian, and dromaeosaurid, hadrosaurid, troodontid, and
tyrannosaurid remains have also been identified. Juvenile material,
although scarce, indicates an assemblage of individuals of different
ages. Specimens showed no strong preferred two-dimensional orientation
but are clearly sorted vertically. Taphonomic and sedimentological
interpretation support a complex pre-burial history of preserved
elements as well as a depositional setting characterized by persistent
waterlogged conditions as those typical of large oxbow-lakes or
marshy/swampy areas, as well as lacustrine settings within an alluvial
plain. Being located more than 450 km inland from the paleo-coastline,
the new bonebed represents one of the farthest-known inland occurrence
of centrosaurines in North America, further supporting the presence of
large aggregations of ceratopsian far from the coastal lowlands of the
Western Interior Seaway.