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Troodontidae (Theropoda) from Upper Cretaceous of Uzbekistan
A new paper:
Alexander Averianov & Hans-Dieter Sues (2016) [2015)
Troodontidae (Dinosauria: Theropoda) from the Upper Cretaceous of Uzbekistan.
Cretaceous Research 59: 98-110
To date three taxa of troodontid theropod dinosaurs have been
recognized from Upper Cretaceous strata in two regions of the Kyzylkum
Desert in Uzbekistan. The Cenomanian Khodzhakul Formation in the
southwestern Kyzylkum Desert has yielded isolated serrated teeth and
some postcranial bones of an indeterminate troodontid. In the central
Kyzylkum Desert troodontids are known from the Cenomanian Dzharakuduk
Formation (Urbacodon itemirensis) and the Turonian Bissekty Formation
(Urbacodon sp.). Urbacodon itemirensis is known from a single dentary
whereas Urbacodon sp. is represented by isolated teeth, maxilla and
dentary fragments, a partial braincase, and some postcranial bones.
The troodontid affinities of Urbacodon are supported by several
synapomorphies: presence of a subotic recess; reduced basal tubera
placed directly under the occipital condyle; maxilla participating in
the margin of the external naris; nutrient foramina on dentary
situated within a deep lateral groove; dentary without distinct
interdental plates; large number of small dentary and maxillary teeth;
teeth constricted between root and crown; anterior dentary teeth
smaller, more numerous, more closely spaced than those in the middle
of the tooth row, and implanted in a groove; posterior dorsal
vertebrae with tall and posterodorsally tapering neural spines; and
presence of a midline sulcus on the neural arches of distal caudals.
Among Troodontidae, Urbacodon resembles Byronosaurus, Gobivenator, and
Xixiasaurus in the absence of serrations on the tooth crowns and
having premaxillary teeth that are D-shaped in cross-section. However,
phylogenetic analysis did not recover a clade of Asiatic troodontids
with unserrated teeth.