Talos sampsoni, a new troodontid from Utah

After the Chinese Linhevenator, yet, another troodontid, Talos sampsoni, has just been described in the current issue of PLoS ONE. This one is from the distinct and quite specific fauna of the Kaiparowits formation of Utah, which included the unique ceratopsians Kosmoceratops, Utahceratops and Nasutuceratops, the tyrannosaurid Teratophoneus, the hadrosaur Gryposaurus and the Oviraptosaur Hagryphus. Talos is essentially known from remains of the hindlimbs plus a few other bits such as some  vertebrae, and a left ulna. It was probably similar in shape to the other derived troodonts with short forelimbs, long legs and had a sickle claw on each foot.

 

References:
Lindsay E. Zanno, David J. Varricchio, Patrick M. O'Connor, Alan L. Titus and Michael J. Knell. 2011. A new troodontid theropod, Talos sampsoni gen. et sp. nov., from the Upper Cretaceous Western Interior Basin of North America. PLoS ONE 9 (6): e24487.

Linhevenator tani, a new troodontid from China

Fig 1.- Reconstruction of Linhevenator tani.

Troodontids are a family of very bird-like small theropods with long legs and enlarged braincases.  Phylogenetically, they are placed alongside the dromaeosaurs (Velociraptor, Deinonychus and friends) among the Deinonychosaurians, a sister group to the birds. Fossils of troodonts were found in Asia, Europe and North America in sediments dating from the Upper Jurassic to the Upper Cretaceous periods. Some of the better known troodonts include the Early Cretaceous Mei long (the shortest name given to a dinosaur, and meaning “sleeping dragon” because its exceptionally preserved articulated skeleton has been found in a sleeping position) and the Late Cretaceous Troodon formosus from North America, which was originally described on the basis of a single characteristic serrated tooth, but which is now known from multiple fragmentary specimens (previously referred as "Stenonychosaurus").

Fig 2.- The holotype (LH V0021) of Linhevenator tani (Xu et al., 2011). Licensed under CC 2.5. Scale bar is 2 cm.

Xing Xu and colleagues are reporting in the September 2011 issue of the open access journal PLoS ONE, a new troodontid from the Late Cretaceous Wulansuhai Formation of Bayan Mandahu, Inner Mongolia. The Wulansuhai Formation is equivalent to the famous Mongolian dinosaur bearing Djadokhta Formation of Campanian age. This new species, Linhevenator tani is known from a partly articulated skeleton that includes the skull, several vertebrae, pelvic girdle and limb elements. Although badly weathered, the remains are of particular interest are they are to date the most complete ones from a Late Cretaceous Troodontid and therefore likely to shed new lights on the more derived members of this family. Linhevenator was a rather large species (around 2-3 meters in length) characterized by rather short arms (the humeri measured only 40% of the length of the femur) and with a sickle clawed second digit on each foot similar to those of the dromaeosaurs, although these may be in fact common traits to all derived troodontids such as Troodon and Saurornithoides.

References:
Xing Xu, Qingwei Tan, Corwin Sullivan, Fenglu Han and Dong Xiao. 2011. A Short-Armed Troodontid Dinosaur from the Upper Cretaceous of Inner Mongolia and its Implications for Troodontid Evolution. PLoS ONE 6 (9): e22916

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