New large-clawed Jurassic dinosaur sheds light on elusive lineage

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A new alvarezsauroid dinosaur is being published in the Journal Science tommorrow.The 160 MYA specimen is named Haplocheirus sollers ("simple, skillful hand").

This is an important discovery as its age means that it is 63 million years older than its nearest known relatives, and also lived a full 15 million years before Archaeopteryx. The discovery removes any remaining doubt about the positioning of Alvarezsaurs in the therapod family.

http://www.scientificamerican.com/blog/post.cfm?id=new-large-clawed-jurassic-dinosaur-2010-01-28

"What Haplocheirus definitively shows," said Choiniere, "is that alvarezsauroids aren't birds. They're theropod dinosaurs, so they're closely related to birds, but they aren't actually an offshoot of birds themselves."

The ancient age of Haplocheirus "really extends our fossil records," Choiniere said in the interview with Science. As he noted in a prepared statement, "Haplocheirus is a transitional fossil because it shows an early evolutionary step in how the bizarre hands of later alvarezsaurs evolved from earlier predatory dinosaurs." By 160 million years ago, the new genus already had the short arms and long middle claw typical of later alvarezsauroids, but its arms are longer and the claw is a little shorter than the later, Cretaceous species.