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Study traces dinosaur evolution into early birds



By SETH BORENSTEIN

WASHINGTON (AP) - Scientists have mapped how a group of fearsome, massive dinosaurs evolved and shrank to the likes of robins and hummingbirds.

Comparing fossils of 120 different species and 1,500 skeletal features, especially thigh bones, researchers constructed a detailed family tree for the class of two-legged meat-eaters called theropods. That suborder of dinos survives to this day as birds, however unrecognizable and improbable it sounds.

The steady downsizing and elegant evolution of the theropods is detailed in the journal Science on Thursday.

"They just kept on shrinking and shrinking and shrinking for about 50 million years," said study author Michael S. Y. Lee of the University of Adelaide in Australia. He called them "shape-shifters."

Lee and colleagues created a dinosaur version of the iconic ape-to-man drawing of human evolution. In this version, the lumbering large dinos shrink, getting more feathery and big-chested, until they are the earliest version of birds.

For a couple decades scientists have linked birds to this family of dinosaurs because they shared hollow bones, wishbones, feathers and other characteristics. But the Lee study gives the best picture of how steady and unusual theropod evolution was. The skeletons of theropods changed four times faster than other types of dinosaurs, the study said.

A few members of that dino family did not shrink, including T. rex, which is more of a distant cousin to birds than a direct ancestor, Lee said.

He said he and colleagues were surprised by just how consistently the theropods shrank over evolutionary time, while other types of dinosaurs showed ups and downs in body size.

The first theropods were large, weighing around 600 pounds. They roamed about 220 million to 230 million years ago. Then about 200 million years ago, when some of the creatures weighed about 360 pounds, the shrinking became faster and more prolonged, the study said. In just 25 million years, the beasts were slimmed down to barely 100 pounds. By 167 million years ago, 6-pound paravians, more direct ancestor of birds, were around.

And 163 million years ago the first birds, weighing less than two pounds, probably came on the scene, the study said

Paul Sereno, a dinosaur researcher at the University of Chicago who wasn't part of this study, praised Lee's work as innovative.

The steady size reduction shows "something very strange going on," Sereno said. "This is key to what went on at the origin of birds."

People may think bigger is better, but sometimes when it comes to evolution smaller can be better because bigger creatures are more likely to go extinct, Sereno said.

And when the theropods started shrinking there weren't many other small species that would compete with them, Lee said.

"The dinosaur ancestors of birds found a new niche and a new way of life," Lee said.

Sereno added, "When you are small, it's a totally different ball game. You can fly and glide and I think that's what drove it."

Join the discussion

1000|Char. 1000  Char.
apaverman August 02 2014 at 7:37 AM

im 60yrs old and new this 50 yrs ago

Flag Reply +22 rate up
11 replies
boricuainmotion August 02 2014 at 9:07 AM

The claim that an animal changed from one species into another over a period of millions of years is unscientific and unobservable according to science
standards.It has never been observed anywhere. Just another excuse to avoid accountability to their CREATOR!

Flag Reply +17 rate up
32 replies
IBruzEZ August 02 2014 at 9:27 AM

Not science at all, just more mumbo-jumbo evolution imagination.!! 1) take any given species 2)make up a bunch of nonsense drawings 3) claim it is "proven fact". LOL.... !!!

Flag Reply +14 rate up
12 replies
thorrsman August 02 2014 at 7:14 AM

HP once again dumbs down a scientific article to the point of uselessness.

Flag Reply +13 rate up
3 replies
mflmarlton August 02 2014 at 2:18 PM

You Creationist just don't get it. How many ape's and monkeys are alive today? How many different types do you think have lived and died over the last 50 million years or so? Is it so hard to grasp that significant changes have accured within all species that survived the many changes that the earth has seen over the millennia. Why is it that Creationist seem that when human evolution is talked about they assume scientist are speaking that we're directly evolved from modern day gorillas or chimpanzees? Oh, sorry. You probably couldn't get by the 50 million years? According to the thumpers you believe the earth is only 6,000 years old and Fred Flintstone really did drive a dinosaur to work.

Flag Reply +9 rate up
8 replies
Mr. Alan August 02 2014 at 8:39 AM

Almost funny. Science finally catches up with the science fiction of Jurassic Park.

Flag Reply +9 rate up
2 replies
cbza3600 Mr. Alan August 02 2014 at 10:11 AM

the best science fiction has always been the most prophetic

Flag Reply 0 rate up
powermetal38 Mr. Alan August 02 2014 at 10:14 AM

Ya think...they are close to making another mammoth...then I think we will have you science fiction !

Flag Reply 0 rate up
Bob August 02 2014 at 9:40 AM

Yea, just yesterday while walking down the street I saw a Priest turn into a Bar.

Flag Reply +8 rate up
3 replies
Jeremiah August 02 2014 at 9:47 AM

Tell us something we didn't know.

Flag Reply +6 rate up
2 replies
powermetal38 Jeremiah August 02 2014 at 10:15 AM

What ?

Flag Reply 0 rate up
1 reply
thezestyitalian1 powermetal38 August 02 2014 at 2:15 PM

Like what happened before the big bang

Flag 0 rate up
Joesph Jeremiah August 02 2014 at 8:10 PM

Old McDonald was a terrible speller

Flag Reply 0 rate up
Denny August 02 2014 at 9:01 AM

This is not new...just more AOL trash!

Flag Reply +5 rate up
1 reply
traysteph23 Denny August 02 2014 at 4:29 PM

Didn't claim to be new. It clearly states that this information is not new. It is talking about this particular study and how it is the best one to show how the changes from dinosaurs to birds have occurred. Did you read it at all??

Flag Reply 0 rate up
3 replies
CHUCK August 02 2014 at 12:17 PM

Scientist have been saying this since I can remember. A very long time. This is nothing new.

Flag Reply +4 rate up
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