This dinosaur not only helps piece together an evolutionary puzzle, but also answers the age old question, "Which came first, the finger or the claw?"
Portia Sloan
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THE GIST:
- A new dinosaur sheds light on the evolutionary link between dinosaurs and birds.
- The stubby-armed, toothy dino had a huge middle finger.
- This finger likely represented an early evolutionary stage for a massive claw found in later dinos.
The extended bird family tree just gained a new and distinctive member, according to an international team of scientists.
They have found a long-legged, toothy, stubby-armed, three-fingered dinosaur that was an important early member of the lineage that includes birds and their closest dino relatives.
The 160-million-year-old dinosaur, Haplocheirus sollers , is about 10 million years older than what is believed to be the world's first known bird, Archaeopteryx . It exhibits characteristics associated with both dinos and birds, but the new dinosaur was not a very close relative to birds, as some researchers had previously thought.
Nevertheless, the new species helps to fill in the fossil record and cement the long-held view that birds did indeed emerge out of the Maniraptora "hand snatcher" clade.
"Many dinosaurs are very bird-like and early birds are dinosaur-like," co-author Xing Xu told Discovery News, adding that there is still debate over the exact moment when birds first emerged.
"It is more or less depending on what you call a bird a bird, which is somewhat an arbitrary procedure," said Xu, a professor in the Institute of Vertebrate Paleontology & Paleoanthropology at the Chinese Academy of Sciences. "For example, Epidexipteryx (a small, feathered "dinosaur") could be considered to be the earliest representative of the avian lineage."
For the study, published in the latest issue of Science , Xu and his colleagues, led by Jonah Choiniere of The Washington University, analyzed the new dinosaur, discovered in orange mudstone beds at Junggar Basin in Xinjiang, China. According to Xu, the researchers determined it was "a relatively small carnivorous dinosaur" about 6.5 feet long with a slender head and "numerous small teeth."
The "hand snatcher" description seems quite appropriate in this case, since the dinosaur's hands had three strong fingers, with the first finger being "much more robust than the others."
" 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 Choiniere. "The fossil also confirms our predictions that Alvarezsauridae should have been evolving in the Late Jurassic time period."
The unusual hands of later alvarezsaurs possessed a single, massive claw that was probably used for digging. The impressive first finger on the recently excavated dinosaur likely represented an early evolutionary stage for this claw.
The new dinosaur, which was big for a bird but small for a dino, shows that both alvarezsauroids and birds shrunk, but independent of each other.
H. sollers is the world's largest and oldest known alvarezsauroid -- 63 million years older than other known members of this group.
A second important dinosaur study this week, published in Nature and again co-authored by Xu, shows how another bird trademark -- feathers -- originated. Scientists previously wondered if they were first used for flight, insulation or display.
"We now know that feathers came before wings, so feathers did not originate as flight structures," said Mike Benton, a professor of paleontology at the University of Bristol who worked on the Nature study. "We therefore suggest that feathers first arose as agents for color display and only later in their evolutionary history did they become useful for flight and insulation."
By analyzing color-bearing organelles buried in the fossils of bird-like dinosaurs and early birds, Benton and his team were even able to reconstruct the color of these prehistoric animals. The dinosaur Sinosauropteryx , for example, sported orange and white rings down its tail. The early bird Confuciusornis , on the other hand, had patches of white, black and orange-brown coloring.
"These discoveries open up a whole new area of research," said Benton, "allowing us to explore aspects of the life and behavior of dinosaurs and early birds that lived over 100 million years ago."