Oct
13
2005

New fossil strengthens link between dinos and birds

Scientists at The Field Museum in Chicago have discovered
a new type of dinosaur,
called Buitreraptor (BWEE-tray-RAP-ter). About the size of a turkey, it was probably covered with feathers and lived in Argentina some 90 million years ago.

Buitreraptor

Buiteraptor is a type of dinosaur known as a dromeosaur., which also includes the famous Velociraptor. Their skeletons are very similar to birds'. In fact, scientists have used them as evidence that birds evolved from dinosaurs-quite possibly from dromeosaurs.

However, there has always been an inconsistency. The earliest known bird is about 150 million years old. The earliest dromeosaurs appeared about 125 million years ago. Kind of hard to be an ancestor if you're younger than your descendents.

But the new fossil changes all that. It's from South America. All previous dromeosaurs had been from North America (or Asia). North and South America split apart some 145 million years ago. So, in order for there to be dromeosuars on both continents, the group must have appeared at least that long ago-which puts them right in the ballpark to be, if not the direct ancesors of birds, then at least very close relatives.

Your Comments, Thoughts, Questions, Ideas

Tom Stephan's picture
Tom Stephan says:

Did buitreraptor have an avian coracoid sternal complex? If so, wouldnt'there have been a more basal dino/ bird?
Beautiful work, congratulations on the person(s) that found it!
Tom Stephan, falconer

posted on Tue, 11/22/2005 - 10:56pm
Gene's picture
Gene says:

Oh, there is definitely a more basal bird. Buitreraptor may look like a bird, but it's actually a dromeosaur, a type of dinosaur. Birds split off from dinosaurs about 150 million years ago. Buitreraptor is only about 90 million years old. So it is not the ancestor of birds.

However, it provides intriguing evidence that some earlier dromeosaur was the ancestor of birds. The reasoning goes like this:

  • The earliest birds are about 150 million years old.
  • The southern continents split away from the northern continents 145 million years ago.
  • The earliest known dromeosaurs are about 125 million years old. (There may be older ones; we just haven't found them yet.) All previous dromeosaur fossils were found in northern continents.

Based on this evidence, some scientists had concluded that dromeosaurs could not have been the ancestors of birds. Their fossils are too young, and the fact that all the finds had been in the northern hemisphere implied that the group evolved after the continents split -- which meant after birds had already appeared.

But this new fossil changes that. It's from South America. Even though it's not the oldest dromeosaur known, the fact that it's in the southern hemisphere means dromeousaurs must have evolved before 145 million years ago. This means dromeosaurs as a group are old enough to be the ancestors of birds. Exactly what that ancestor is remains to be discovered.

posted on Wed, 11/23/2005 - 2:43pm
Kristi Curry Rogers's picture
Kristi Curry Rogers says:

I looked into the anatomy of the sternum of Buitreraptor - here's the story. Buitreraptor has a furcula (a bone that is the same as the wishbone of a modern Thanksgiving turkey). It also has a long, curved, straplike shoulder blade (the scapula). The coracoids are enlarged with an expanded blade and large muscle attachments. This new dromeaosaur is really important, not so much for it's similarity to birds (most paleontologists now agree that birds are really just derived theropod dinosaurs), but for what it tells us about the global distribution of dromaeosaurids - something that you would expect if birds and their dromaeosaurid ancestors evolved before the separation of Pangea into northern (Laurasia) and southern (Gondwana) landmasses.

Kristi Curry Rogers, Ph. D.
Curator of Paleontology
Science Museum of Minnesota

posted on Wed, 11/30/2005 - 2:03pm
Alex Eldridge's picture
Alex Eldridge says:

I am interested in science and I think this is neat.

posted on Tue, 01/31/2006 - 7:08pm
Sawyer stoos's picture
Sawyer stoos says:

The science museum is very helpful.

posted on Thu, 04/05/2007 - 12:46pm
DaMatriX's picture
DaMatriX says:

What about the possibility that birds did not descent from dromaeosaurs, but actually the other way around (e.g. domaeosaurs are birds)? The similarity between Archaeopteryx and primitive dromaeosaurs like Microraptor and Rahonavis may be the result from the fact that primitive dromaeosaurs are actually more derived than Archaeopteryx, which is traditionally seen as the earliest (known) bird. So, according to the cladistic view, dromaeosaurs are members of the class Aves and later forms like Velociraptor and Deinonychus are secondary flightless. In other words: the "mean monster" from Jurassic Park (Velociraptor) may actually may a bad-ass ostrich ;)

posted on Wed, 11/28/2007 - 5:41pm
Gene's picture
Gene says:

That still leaves unresolved the question of where birds came from. And the numerous similarities between dromeosaurs and other dinosaurs indicates a close kinship.

For this alternate theory to be correct, birds would have to have evolved from some other group of dinosaurs which they did not resemble as much, and then evolve back into a form -- dromeosaurs -- that resembles dinosaurs more closely. Evolution doesn't work like that.

posted on Fri, 11/30/2007 - 11:27am

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