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Allosaurus lucasi, new species of theropod from Morrison Formation, Colorado (free pdf)

Ben Creisler

A new paper in open access:

Sebastian G. Dalman (2014)
Osteology of a large allosauroid theropod from the Upper Jurassic
(Tithonian) Morrison Formation of Colorado, USA.
Volumina Jurassica 12 (2): 159-180
DOI : 10.5604/17313708 .1130

Two partial skeletons of allosaurid theropods belonging to an adult
and a juvenile from the Upper Jurassic (Tithonian) Morrison Formation
of McElmo Canyon in Montezuma County, southwestern Colorado, were
discovered in 1953 by the late Joseph T. Gregory and David Techter.
The adult specimen consists of several isolated cranial and
postcranial skeletal elements that are exceptionally well-preserved
and include the left premaxilla, maxilla, dentary, teeth,
quadratojugal, two caudal vertebrae, pubic peduncle, ischium, proximal
tibia, a nearly complete left foot, and several isolated teeth,
whereas the juvenile specimen is represented by the distal portion of
the right dentary and a fragmentary splenial. The specimens represent
a new species of Allosaurus, here named Allosaurus lucasi, which
differs from Allosaurus fragilis by having a relatively short
premaxilla and robust quadratojugal with short jugal process and a
short quadrate process of the quadratojugal that is at the same level
as the rostral quadratojugal ramus. The presence of a new species of
Allosaurus in the Tithonian of North America provides further evidence
of the taxonomic and morphological diversity of the Allosauridae clade
and their continuous evolutionary success, which extended to the