Thursday, February 04, 2010

Haplocheirus sollers

A Basal Alvarezsauroid Theropod from the Early Late Jurassic of Xinjiang, China. 2010. J. N. Choiniere, et al. Science 327: 571 – 574.

Skull of Haplocheirus IVPP V15988 in dorsal view.
The discovery of Haplocheirus sollers (meaning simple, skillful hand) extends the fossil record of the family Alvarezsauridae – a bizarre group of bird-like dinosaurs with a large claw on the hand and very short, powerful arms – back 63 million years, further distancing the group from birds on the evolutionary tree. Until now, there was no direct evidence that dinosaurs of this type lived during the Late Jurassic, approximately 160 million years ago.

The new species shows some of the earliest evolutionary stages in the development of a short, powerful arm with a single functional claw that may have been used for digging termites.

Haplocheirus IVPP V15988 holotype specimen in right lateral view after skull was removed.
"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," said Mr. Choiniere. "The fossil also confirms our predictions that Alvarezsauridae should have been evolving in the Late Jurassic time period." link