RT Journal Article
SR Electronic
T1 A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight
JF Science
JO Science
FD American Association for the Advancement of Science
SP 1378
OP 1381
DO 10.1126/science.1144066
VO 317
IS 5843
A1 Turner, Alan H.
A1 Pol, Diego
A1 Clarke, Julia A.
A1 Erickson, Gregory M.
A1 Norell, Mark A.
YR 2007
UL http://science.sciencemag.org/content/317/5843/1378.abstract
AB Fossil evidence for changes in dinosaurs near the lineage leading to birds and the origin of flight has been sparse. A dinosaur from Mongolia represents the basal divergence within Dromaeosauridae. The taxon's small body size and phylogenetic position imply that extreme miniaturization was ancestral for Paraves (the clade including Avialae, Troodontidae, and Dromaeosauridae), phylogenetically earlier than where flight evolution is strongly inferred. In contrast to the sustained small body sizes among avialans throughout the Cretaceous Period, the two dinosaurian lineages most closely related to birds, dromaeosaurids and troodontids, underwent four independent events of gigantism, and in some lineages size increased by nearly three orders of magnitude. Thus, change in theropod body size leading to flight's origin was not unidirectional.