National Geographic News
An illustration of a theropod dinosaur.

An artist's conception of Aurornis xui, a new early avian theropod from the Middle/Late Jurassic of China.

Illustration courtesy Masato Hattori

Brian Switek

for National Geographic

Published May 30, 2013

For over a century and a half, the prehistoric Archaeopteryx has been celebrated as nature's earliest bird.

The iconic Jurassic creature was covered in feathers yet retained the teeth, claws, and bony tail from its dinosaurian ancestry, known from at least 11 specimens that have been chipped from limestone quarries in Germany. (Related: “Feathered Dinosaur Had Black Wings?”)

But was Archaeopteryx truly an early bird, or just one of many sorts of plumage-coated, non-avian dinosaurs? An archaic bird known as Aurornis xui, described this week in the journal Nature by paleontologist Pascal Godefroit and colleagues, is the latest entry in the debate over which animal qualifies as the first bird and how birds evolved.

The delicately preserved specimen, which includes fossil remnants of feathers, was discovered in the roughly 160-million-year-old rock of China's Tiaojishan Formation. While Aurornis lived about ten million years earlier than Archaeopteryx, and very far from the prehistoric European archipelago that Archaeopteryx inhabited, the new study found that the two plumage-covered creatures were close relatives at the very base of bird evolution.

"It's among the earliest birds, being it's both older and apparently less 'birdlike' than Archaeopteryx along the 'bird branch,'" says study co-author Andrea Cau of Italy's Museo Geologico.

Bird Fights

The close ancestral proximity described in the new paper runs counter to another Nature study, published two years ago, which argued that Archaeopteryx and related dinosaurs were further removed from bird ancestry.

In 2011, paleontologist Xing Xu and colleagues described a similar feathery dinosaur, found in the same formation, that they named Xiaotingia zhengi. This animal also appeared to be a close relative of Archaeopteryx.

But there was a twist in that study: The researchers theorized that Archaeopteryx, Xiaotingia, and yet another similar animal called Anchiornis actually fell outside the bird line and were closer to a branch of non-bird dinosaurs called deinonychosaurs.

That group includes feathery, switchblade-clawed dinosaurs such as Velociraptor and Troodon.

Feathers alone don't make a bird, and the rapid discovery of so many birdlike dinosaurs has spurred debate over how to distinguish between the creatures that truly were early birds and those that merely look like good candidates for archaic avians.

So maybe Archaeopteryx was not an early bird, after all. More than that, Xu and collaborators proposed, maybe the first birds weren't descendents of the deinonychosaurs—as has often been suggested—but instead evolved from poorly known dinosaurs similar to the bucktoothed Epidexipteryx.

Any evolutionary tree is a hypothesis that can change with new evidence and investigation. No wonder, then, that not everyone agreed with the tree that Xu and colleagues proposed.

A quick response using different methods, by Michael Lee and Trevor Worthy, reaffirmed the status of Archaeopteryx as an archaic bird. The new Aurornis paper supports this hypothesis, even as it introduces Aurornis as a candidate for an even older bird.

What's a Bird, Anyway?

The problem for Archaeopteryx, Aurornis, and their relatives, says University of Maryland paleontologist Thomas Holtz, Jr., is that "by being so primitive there is no definite way to place them as stem-birds, stem-deinonychosaurs," or members of another group.

The animals are so close to the base of their lineages that it's difficult to tell exactly where they fit.

Natural History Museum of Los Angeles paleontologist Luis Chiappe agrees, noting that Aurornis is close to bird ancestry but may not actually fall within the actual bird group defined by the last common ancestor of Archaeopteryx and modern birds.

"The problem we are facing these days is that all these animals are anatomically very similar, and our definition of birds—arbitrary as it is—sets a line between what is and what isn't called a bird," Chiappe says.

The sheer number of feathery fossils complicates matters further.

"What the trees—and the new fossils—are telling us is that back in the Jurassic, 150 to 160 million years ago, many different types of dinosaurs were experimenting with 'birdness,'" Chiappe notes. "And it is from this 'birdness soup' that true birds originated."

As frustrating as the identities of Aurornis, Anchiornis, Archaeopteryx, Xiaotingia, Eosinopteryx, and other birdlike dinosaurs are to draw out, the confusion has made a positive contribution to paleontology: The explosion of feathered dinosaur finds and research has left no doubt that birds are dinosaurs.

While Holtz expects that Archaeopteryx, Aurornis, and their relatives "are going to bop back and forth in the early positions on the tree" in future studies, he says that "in the end, it doesn't matter which ones are stem-deinonychosaurs and which stem-birds. Together they show us that the ancestors of pigeons and Velociraptor were small, probably flying, animals that look like these."

Still, figuring out the early bird evolutionary tree does matter in coming up with expectations about how the first avians evolved, particularly the origin of flight. Which one deserves the title of "First Bird," and how that find will shape our understanding of one of the most magnificent evolutionary transformations of all time, will be investigated and debated for many years to come.

12 comments
Charles Weber
Charles Weber

The Cretaceous ocean predators were very large. I suspect that the productivity implied by this was caused by a flow of phosphorus toward the ocean from the savannas (seasonal rainfall areas) permitted by erosion of phosphorus rich runways of plant smothering termites in the Amitermitinae starting in late Jurassic in Australia where the first ocean phosphorite deposits occurred. Anoxic conditions in the oceans were also probably caused by this. This anoxic bottom condition probably helped reduce the ammonites also, in addition to competition from phosphorus enhanced vertebrates. The savanna herbivore dinosaurs declined in armor, teeth, and quite a bit in bony structure across the Cretaceous outside of South America, especially in southeast Asia. Many even lost teeth. I suggest it was due to this same phosphorus famine created by erosion of the soil of the runways of plant smothering termites. Pterosaurs and birds probably lost teeth primarily because of the young eating iron oxide and bauxite in the flying reproductive soil borne termites’ guts, which bound the phosphates. You may see this discussed in more detail starting inhttp://www.angelfire.com/nc/isoptera/termites.htmland its links, which links explore the possible affect that ant evolution had upon them. By the time the Cretaceous ended the world ended up with tiny savanna vertebrates, most of them mammals, which were able to give their young phosphorus in milk at that critical stage. They were a far cry from the massive, well boned Stegosaurs, etc., which roamed around the Jurassic, and had diminished tooth structure at first. They were a long time starting to increase in size (several million years).

        You may see the affects on soil discussed in more detail in http://www.angelfire.com/nc/isoptera/soil.html .

                                     Sincerely, Charles Weber

PSIt is conceivable that you would also find interesting a hypothesis of my son explaining the Decca (or Deccan) lava flows as disruption of the crust by the disruption of the crust at the antipode (opposite side of a sphere) by a huge meteorite impact. You may see my version in http://charles_w.tripod.com/antipode.html .

Sincerely, Charles Weber

Penelope Cooke
Penelope Cooke

why is this item listed under archaeology and not under science?

Akhmad Sidiqi
Akhmad Sidiqi

Is that any fur in his body besides their body?

Nick Danger3rdeye
Nick Danger3rdeye

Looks, and probably tastes, like angry chicken.

I've heard the creationist argument that there are no midstages between dinosaur and bird, because there are no midstages between flightless and gliding/flight.  But chickens use their feathered wings as 'air oars' to gain speed when running, and to help them hop to a taller roost that would otherwise be unavailable.  (Hard not to sneak in a WKRP joke here.)

Babu Ranganathan
Babu Ranganathan

NOT DINOSAUR FEATHERS!

All this talk of dinosaurs having feathers is nonsense and is not even accepted by most evolutionists. Some evolutionists have a certain interpretation of a fossil and this interpretation becomes extrapolate beyond into imagination and then you have artists giving expression to that imagination, but the media is all for such "news." Please read my popular Internet articles below.

Recently, it was thought they had discovered fossils of dinosaurs with feathers until they found out that many of the so-called feathers were actually scales. The scales took upon a feather-like appearance during the fossilization process. There's strong evidence that other structures interpreted as feathers are woolly plumages and collagen fibers. A few evolutionists (not even most) interpret these structures as proto-feathers and have artists drawing dinosaurs with fancy feathers for magazines and newspapers!


TALES OF FISH LEGS AND DINOSAUR FEATHERS, NO HALF-EVOLVED DINOSAURS, NATURAL LIMITS OF EVOLUTION, WAR AMONG EVOLUTIONISTS (2nd Edition), DOES GOD PARTICLE EXPLAIN UNIVERSE'S ORIGIN?, THE SCIENCE SUPPORTING CREATION, HOW FORENSIC SCIENCE REFUTES ATHEISM, ARE FOSSILS REALLY MILLIONS OF YEARS OLD.

Visit my newest and very popular Internet site: THE SCIENCE SUPPORTING CREATION

Sincerely,
Babu G. Ranganathan*
(B.A. theology/biology)

I am author of the popular Internet article: TRADITIONAL DOCTRINE OF HELL EVOLVED FROM GREEK ROOTS
* I have had the privilege of being recognized in the 24th edition of Marquis "Who's Who in The East" for my writings on religion and science, and I have given very successful lectures (with question and answer time afterwards) before evolutionist science faculty and students at various colleges and universities.

Patrick Whalen
Patrick Whalen

Couldn't we distinguish stem-deinonychosaurs and  stem-birds by the ability to fly? Figuring out which actually flew and didn't is for some one else tho :)

C. Dufour
C. Dufour

@Babu Ranganathan For someone who feels he has enough credentials that he needs to boast about them in his signature, you sure make a lot of spelling mistakes.... not to mention mistakes in understanding basic evolutionary processes.

Matt McDowall
Matt McDowall

@Babu Ranganathan  

You sir are an embarrassment.

Even if your credentials are correct...a bachelor degree of biology with an even laughable theology...

heres a tip - why don't you listen to the professionals, you know the ones with more than a lame bachelor degree, and without a bias (theology - or should I say the study of nothing) and let them educate you.



C. Dufour
C. Dufour

@Patrick Whalen but then it becomes blurry as some branches of flying dinosaurs didn't actually evolve into birds (their branches died out) but some modern birds don't fly either such as ratites. 

I think morphology of the downstroke necessary for powered flight might be the best factor for bird evolution.

Barb Burk
Barb Burk

@Matt McDowall @Babu Ranganathan 

Professionals???

"There is the problem.  Are these dinosaurs with feathers?  The possibility would be they are not dinosaurs; they are very primitive birds...sometimes science needs a headline - Feathered Dinosaur...in order to get attention and in the end to get ...financial support..."
Dr. Peter Wellnhofer; Curator Emieritus , Bavarian State Collection of Paleontology, Munich

"The idea of feathered dinosaurs and the theropod origin of birds is being actively promulgated by a cadre of zealous scientists acting in concert with certain editors at Nature and National Geographic who themselves have become outspoken and highly biased proselytizers of the faith." Stors Olson, Curator of Birds, National Museum of Natural History, Smithsonian Institution.

Want more????  It all depends which side of the fence you're on. 


Share

Feed the World

  • How to Feed Our Growing Planet

    How to Feed Our Growing Planet

    National Geographic explores how we can feed the growing population without overwhelming the planet in our food series.

See blogs, stories, photos, and news »

Latest Photo Galleries

See more photos »

Shop Our Space Collection

  • Be the First to Own <i>Cosmos: A Spacetime Odyssey</i>

    Be the First to Own Cosmos: A Spacetime Odyssey

    The updated companion book to Carl Sagan's Cosmos, featuring a new forward by Neil deGrasse Tyson is now available. Proceeds support our mission programs, which protect species, habitats, and cultures.

Shop Now »