[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

An alvarezsaurid from the beginning of the Late Jurassic



As I just mentioned...

Jonah Choiniere, James Clark, Xu Xing & Han Fenglu (2009): A new basal alvarezsaur from the Shishugou Formation, online-only supplement to JVP 29(3), 77A & 78A

>>
The Alvarezsauridae are a Cretaceous clade of theropod dinosaurs with highly modified forelimbs. The phylogenetic position of the Alvarezsauridae has been uncertain, with inital systematic research positing them as basal avialians, other analyses finding a sister-group relationship between Ornithomimosauria and Alvarezsauridae, and some recent analyses placing the family at the base of Maniraptora. The latter phylogenetic hypothesis implies that a ghost lineage of over 60 million years exists between the Alvarezsauridae and the oldest-known maniraptorans (Scansoriopterygidae). We report here on a complete specimen of a new basal alvarezsaur from the Shishugou Formation in Xinjiang, China. Extensive radiometric dating of Shishugou volcanic tuffs constrains the age of the specimen to between 158.7 +/- 0.3 mya and 161.2 +/- 0.2 mya, approximately at the beginning of the Late Jurassic. This new taxon extends the stratigraphic range of the Alvarezsauridae by 60 million years, provides new information about alvarezsaur morphological evolution, confirms a basal position for the Alvarezsauridae within the Maniraptora rather than within Avialae or sister to Ornithomimosauria, and indicates that the earliest members of the family were not
Gondwanan, as previous studies have suggested.
<<

Another paper to wait for. :-)

I think I can say that the poster showed a fairly complete and very well-preserved skeleton.