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Re: [dinosaur] Latenivenatrix, new troodontid from Dinosaur Park Formation, Alberta (validity of Troodon)



In the 2nd edition of my field guide I provisionally revived Stenonychosaurus inequalis in part because of my policy of not including taxa founded on teeth that have not been officially transferred to skeletal remains (as per Iguanodon). What is cool about this paper is that they pin down S. inequalis to the lower DinoPark formation (for some reason I had it high in the formation), and note it may be the same as the Two Medicine material. 

Paul


-----Original Message-----
From: Ben Creisler <bcreisler@gmail.com>
To: dinosaur-l <dinosaur-l@usc.edu>
Sent: Tue, Aug 8, 2017 12:02 pm
Subject: [dinosaur] Latenivenatrix, new troodontid from Dinosaur Park Formation, Alberta (validity of Troodon)




Ben Creisler


A new paper:


Latenivenatrix mcmasterae gen. nov. & spec. nov.

Stenonychosaurus inequalis valid

Troodon formosus nomen dubium?


Aaron J. van der Reest & Philip J. Currie (2017)
Troodontids (Theropoda) from the Dinosaur Park Formation, Alberta, with a description of a unique new taxon: implications for deinonychosaur diversity in North America.
Canadian Journal of Earth Sciences (advance online publication)




Troodontids are known from Asia and North America, with the most complete specimens from the Jurassic of China and the Cretaceous of Mongolia. North American troodontids are poorly known, and specimens that have been described are isolated elements or partial skeletons with limited material. A new troodontid from the upper Dinosaur Park Formation (upper Campanian) is based on partial skulls, several vertebrae, ribs, gastralia, chevrons, a sacrum, partial pelvis, and partial fore and hind limbs. It is the largest troodontid known, with an estimated height of 180 cm and length of 350 cm. Like other troodontids, it possesses an elongated ambiens process and has a horizontal ventral margin of the postacetabular process. It differs from all other derived troodontids in that the slightly retroverted pubis has a shaft that curves anteroventrally. Some specimens from the Dinosaur Park Formation previously assigned to Troodon are reassigned to the new taxon, including multiple partial crania, an associated dentary and metatarsus, and a partial skeleton. Previously undescribed elements from the lower part of the Dinosaur Park Formation are assigned to the resurrected Stenonychosaurus inequalis. Distinct stratigraphic separation of Stenonychosaurus inequalis and the new taxon indicates a replacement in troodontid fauna, similar to the turnover of large ornithischians in the same formation. The new taxon is phylogenetically more closely related to Mongolian taxa, indicating the replacement of Stenonychosaurus may have been from an earlier Asian form immigrating into North America.


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