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Dinosaur Biostratigraphy of the Edmonton Group, Alberta, Canada:



From: Ben Creisler
bcreisler@gmail.com

A new online paper:

David A. Eberth, David C Evans, Donald Brinkman, Francois Therrien,
Darren H.T. Tanke & Loris S. Russell (2013)
Dinosaur Biostratigraphy of the Edmonton Group (Upper Cretaceous),
Alberta, Canada: Evidence for Climate Influence.
Canadian Journal of Earth Sciences,
doi:10.1139/cjes-2012-0185
http://www.nrcresearchpress.com/doi/abs/10.1139/cjes-2012-0185#.UTTShaKHuaY


A high-resolution biostratigraphic analysis of 287 dinosaurian
macrofossils and 138 bonebeds in the Edmonton Group (Upper Cretaceous)
of southern Alberta provides evidence for at least three dinosaurian
assemblage zones in the Horseshoe Canyon Formation (HCFm). From bottom
to top the zones comprise unique assemblages of ornithischians and are
named as follows: 1) Edmontosaurus regalis-Pachyrhinosaurus canadensis
(lower zone); 2) Hypacrosaurus altispinus-Saurolophus osborni (middle
zone); and 3) Eotriceratops xerinsularis (upper zone). Whereas the
lower and middle zones are well-defined and based on abundant
specimens, the validity of the uppermost zone (E. xerinsularis) is
tentative because it is based on a single specimen and the absence of
dinosaur taxa from lower in section. The transition from the lower to
the middle zone coincides with the replacement of a warm-and-wet
saturated deltaic setting by a cooler, coastal-plain landscape,
characterized by seasonal rainfall and better-drained substrates.
Whereas changes in rainfall and substrate drainage appear to have
influenced the faunal change, changes in mean annual temperature and
proximity to shoreline appear to have had little influence on faunal
change. We speculate that the faunal change between the middle and
upper zones also resulted from a change in climate, with ornithischian
dinosaurs responding to the re-establishment of wetter-and-warmer
climates and poorly-drained substrates. Compared with the
shorter-duration and climatically-consistent dinosaurian assemblage
zones in the older Dinosaur Park Formation of southern Alberta, HCFm
assemblage zones record long-term morphological stasis in dinosaurs.
Furthermore, the coincidence of faunal and paleoenvironmental changes
in the HCFm suggest climate-change-driven dinosaur migrations into and
out of the region.