Dinosaur-bird missing link possibly found

<body leftmargin="0" bgcolor="#000060" text="#FFFFFF" link="#FFFF00" vlink="#FF9900"> <b> <p class="MsoNormal"><font face="Arial" size="4">Dinosaur-bird missing link possibly found</font></p> </b> <p class="MsoNormal"><font face="Arial" size="1">Posted Feb. 16, 2005<br> Special to  World Science</font> <b> <font size="2" face="Arial"><br> <br> Researchers say they’ve discovered a partial fossil of a feather-footed creature possibly similar to the species of dinosaur that evolved into birds. <br> <br> </font></b> </p> <p class="MsoNormal"><b> <font size="2" face="Arial">While not the first bird-like dinosaur fossil found, this one may be more closely related to the direct dinosaur ancestor of birds than any other yet unearthed, the researchers said. That’s because previous findings involved dinosaurs that lived at the same time as primitive birds, rather than before them, and thus might have been “irrelevant” to the dinosaur-bird transition, the researchers said.<br> <br> The new finding thus goes further than any previous one towards confirming a theory—believed by most, but not all, paleontologists—that birds descend from dinosaurs, the researchers said. It could also reveal more about how bird flight originated and precisely which type of dinosaur gave rise to the bird lineage, they added.<br> <br> For one thing, they asserted, the finding suggests birds originated in Laurasia, a ancient super-continent composed of present-day Eurasia, North America and Greenland. The available evidence “perhaps tentatively supports an Asian origin” of birds, wrote the researchers in a paper on their findings, published in the Feb. 1 issue of the journal Natural Sciences.<br> <br> The specimen, from a fossil-rich bed of rock near the village of Daohugou, China, is of an animal apparently slightly shorter than 1 meter (about 1 yard) long, said the researchers. The fossil shows only a leg with long, lush, bird-like feathers.<br> <br> The rock beds, called the Daohugou beds, seem, based on the fossils in them, to have formed during the middle or later part of the Jurassic period, the researchers said. The Jurassic is a period between 208 million and 146 million years ago, when birds and flowering plants are believed to have evolved, and when many dinosaurs flourished.<br> <br> The Jurassic period is of course the time period referred to in the Steven Spielberg movie Jurassic Park. Birds are in fact believed to be closely related to one of the dinosaur stars of that movie, the fleet-footed Velociraptor. <br> <br> Velociraptor—which looks something like a little <i> Tyrannosaurus Rex</i> that may have made up in zippiness what it lacked in size—was a member of a family of smart, vicious dinosaurs called dromaeosaurs. The previous findings of bird-like dinosaur fossils, announced in 2003, were identified as particularly small representatives of this group. They were most remarkable in that they had four wings. Both their front and hind limbs had each developed into a pair of wings.<br> <br> These microraptors were dated at about 126 million years old, some 25 million years younger than the oldest known bird, Archaeopteryx. Thus, lived to late to have been bird ancestors.<br> <br> The new finding doesn’t have that drawback, according to the researchers who made both discoveries, Xing Xu and Fucheng Zhang of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, Beijing.<br> <br> They said the newly discovered creature, dubbed <i> Pedopenna daohugouensis</i> (“the feather-footed one from Daohugou”) is a primitive member of a family of dinosaurs called eumaniraptora, the researchers said. <br> <br> This group, they added, is both larger and older than the dromaeosaurs, but includes and gave rise to both them and the birds. Eumaniraptora also includes the troodontids, a family of long-legged, fast dinosaurs thought to have had large brains and excellent sight, hearing and hand coordination.<br> <br> If this picture is correct, then, birds would have evolved from a creature similar the common ancestor of all the eumaniraptora, an animal not unlike <i> P. daohugouensis</i>. <br> <br> Moreover, the finding adds to a trend: the most primitive examples of the various members of eumaniraptora and their relatives come from eastern Asia, the researchers wrote. This is what suggests, to them, that birds originated in this area, which at the time was part of the supercontinent of Laurasia.<br> <br> The discovery also adds to evidence, which also appeared with the 2003 findings, that birds’ dinosaur ancestors had feathers both on their front and hind limbs, according to the researchers. Since this feather arrangement forms a structure ideal for gliding, the way flying squirrels move among trees, it supports a hypothesis that the most primitive birds learned to fly this way, the researchers added. <br> <br> However, <i> P. daohugouensis</i> has shorter leg feathers than the previously described specimens, the researchers said. Thus it might represent an evolutionary stage in which the birds’ ancestors were already losing their leg feathers and shifting to an arrangement in which only the front limbs handled the task of flying.</font> </p> </b> </body>