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Tyrannosaurus rex from Lance Formation of Wyoming

From: Ben Creisler

A new paper:

Sebastian G. Dalman (2013)
New Examples of Tyrannosaurus rex from the Lance Formation of Wyoming,
United States.
Bulletin of the Peabody Museum of Natural History 54(2):241-254. 2013
doi: http://dx.doi.org/10.3374/014.054.0202

The dinosaur remains from the Upper Cretaceous Lance Formation of
Wyoming, USA, have been known since 1870. Most of the fossils that are
attributed to theropod dinosaurs are fragmentary skeletons consisting
of cranial, axial and appendicular elements, and many isolated teeth
are also known. The largest known theropod of the Lance Formation
dinosaur fauna is Tyrannosaurus rex. Numerous specimens of this taxon
are known from the Maastrichtian strata of the northwestern United
States and southwestern Canada. In 1890 and 1892, two pedal phalanges
of the left foot and several isolated teeth identified here as
belonging to Tyrannosaurus were discovered near Lusk, Wyoming, by John
Bell Hatcher and the prospecting party from Yale University's Peabody
Museum of Natural History in New Haven, Connecticut, USA. The
discovery of these fossils is significant. One of the first
discoveries of Tyrannosaurus from Wyoming, it predates all other
discoveries and naming of this taxon in the coeval Hell Creek
Formation of Montana, North Dakota and South Dakota, USA, and the
Willow Creek and Scollard formations of the province of Alberta,
Canada. Additionally, a well-preserved anterior end of the right
dentary with teeth discovered in 1947 of a large Tyrannosaurus from
the Lance Formation of the Bighorn basin, Wyoming, is described. The
discovery of this specimen is also significant, because it is the
first occurrence of Tyrannosaurus in the upper coastal plain
paleoenvironments located farther inland away from the coastline of
the Western Interior Seaway. Previous discoveries of Tyrannosaurus
fossil remains from the Lance Formation were from strata deposited
near the coastline of the Western Interior Seaway. The discovery of
these specimens and their lack of significant morphologic divergence
from other specimens of T. rex suggest that this taxon is the only
large-bodied theropod that is currently known from the Upper
Cretaceous (late Maastrichtian) of northwestern North America.