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Osteology of Linhenykus


Osteology of the alvarezsauroid Linhenykus monodactylus from the Upper 
Cretaceous Wulansuhai Formation of Inner Mongolia, China, and comments on 
alvarezsauroid biogeography.

Xing Xu, Paul Upchurch, Qingyu Ma, Michael Pittman, Jonah Choiniere, Corwin 
Sullivan, David W. E. Hone, Qingwei Tan, Lin Tan, Dong Xiao, and Fenglu Han

Acta Palaeontologica Polonica in press
available online 13 Dec 2011 doi:10.4202/app.2011.0083

The alvarezsauroid Linhenykus monodactylus from the Upper Cretaceous of Inner 
Mongolia, China is the first known monodactyl non-avian dinosaur, providing 
important information on the complex patterns of manual evolution seen in 
alvarezsauroids. Here we  provide a detailed description of the osteology of 
this taxon.  Linhenykus shows a number of features that are transitional 
between parvicursorine and non-parvicursorine alvarezsauroids, but detailed 
comparisons also reveal that some characters had a more complex distribution. 
We also use event-based tree-fitting to perform a quantitative analysis of 
alvarezsauroid biogeography incorporating several recently discovered taxa. The 
results suggest that there is no statistical support for previous biogeographic 
hypotheses that favour pure vicariance or pure dispersal scenarios as 
explanations for the distributions of alvarezsauroids across South America, 
North America and Asia. Instead, statistically
 significant biogeographic reconstructions suggest a dominant role for 
sympatric (or ‘within area’) events, combined with a mix of vicariance, 
dispersal and regional extinction. At present the alvarezsauroid data set is 
too small to completely resolve the biogeographic history of this group: future 
studies will need to create larger data sets that encompass additional clades.