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On the Origin of Birds

The discovery of a new bird-like fossil challenges longstanding theories about which species of dinosaur gave rise to the avian lineage.

By | July 27, 2011

Xiaotingia zhengi skeletonXU ET AL. NATURE

This year marks the 150th anniversary of the discovery of one of the most iconic dinosaur fossils of all time: Archaeopteryx. Unearthed in 1861 in southern Germany, it has long been considered the missing link between dinosaurs and birds: it has the skeleton of a reptile—including a long bony tail and teeth—combined with what are considered hallmarks of modern birds—feathers and a wishbone.

But the discovery of a new bird-like dinosaur, Xiaotingia zhengi, in China threatens to dethrone Archaeopteryx as the most primitive of birds.

The inclusion of the new fossil in a comprehensive phylogenetic analysis of dinosaurs and early birds, published today (July 27) in Nature, resulted in a rearrangement of evolutionary relationships—removing Archaeopteryx from the avian family and placing it in a closely related family of non-avian dinosaurs.

“For the past 150 years, Archaeopteryx has been this filter through which we’ve run every idea about the early evolution of birds,” said Lawrence Witmer, a paleontologist at Ohio University who was not involved with the study. The new fossil will force researchers to re-evaluate avian origins from a different perspective, he added.

Roughly the size of a chicken, Xiaotingia zhengi is morphologically very similar to Archaeopteryx, sporting long arms and (most likely) four wings. Like Archaeopteryx, it also walked, or possibly glided, across the Earth during the Late Jurassic Period around 150 million years ago—right at the genesis of birds.

“It’s an amazing fossil,” said lead author Xing Xu, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology in China. “The information recovered from this fossil will have a tremendous impact on our understanding of bird origins.”

Artist’s impression of Xiaotingia zhengi
Artist’s impression of Xiaotingia zhengi
XING LIDA AMD LIU YA

Xu first stumbled upon this new specimen in 2009 during a visit to the Shandong Tianyu Museum of Nature, where it was mistakenly classified as another bird-like dinosaur species, Anchiornis (first described by Xu a few years earlier). But Xu immediately realized this one was different, and represented yet another feathered dinosaur from the Jurassic Period.

A phylogenetic analysis of 374 morphological characters from 89 species of dinosaurs and primitive birds, including Xiaotingia, revealed that Xiaotingia, Archaeopteryx, and Anchiornis all belonged to a small family right at the base of the Deinonychosauria lineage—a group of non-avian, yet bird-like dinosaurs that includes the famous velociraptor featured in the 1993 movie Jurassic Park. When the researchers repeated the analysis excluding Xiaotingia from the dataset, however, Archaeopteryx reverted right back to the avian group, as previous analyses had predicted.

“We are so close to the evolutionary origin of all of these different groups that one fossil can tip the balance,” Witmer said. “These results suggest that Xiaotingia is the linchpin.”

The new phylogeny could have several implications about avian evolution, including what ancient birds may have eaten. While recent studies have suggested that early birds were herbivores, the skull of Archaeopteryx was more suited for a meat-eating diet, leading scientists to believe that birds had started out as meat-eaters and then evolved an herbivorous diet. But removing Archaeopteryx as a direct ancestor of the group suggests that the first birds could have in fact been plant-eaters.

This is not the first time Archaeopteryx’s place at the base of the avian family tree has come under fire. Over the past two decades, scientists have discovered a new crop of dinosaur skeletons with bird-like features that have called into question Archaeopteryx’s missing link status. “A lot of the uniquely avian features that Archaeopteryx has have turned out to be not so unique after all,” Witmer said. As he wrote in Nature’s accompanying editorial, “perhaps the time has come to finally accept that Archaeopteryx was just another small, feathered, bird-like theropod fluttering around in the Jurassic.

Of course, a new fossil may rearrange the evolutionary relationships once again, he added. “In some respects the major story here is just how tangled the knot near the origin of birds and bird-like dinosaurs really was.”

X. Xu et. al., "An Archaeopteryx-like theropod from China and the origin of Avialae," Nature, doi:10.1038/nature10288, 2011.

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Avatar of: Chalcedon

Chalcedon

Posts: 4

July 28, 2011

Arrrggghhhh............the R word repltile/reptilian was used. They were not reptiles they were dinosaurs, an important distinction as there is overwhelming evidence they were warm blooded (endothermic) just like mammals and the birds derived from them through evolution.

Avatar of:

Posts: 0

July 28, 2011

Arrrggghhhh............the R word repltile/reptilian was used. They were not reptiles they were dinosaurs, an important distinction as there is overwhelming evidence they were warm blooded (endothermic) just like mammals and the birds derived from them through evolution.

Avatar of: Bill Th

Anonymous

July 28, 2011

What makes Archaeopteryx "non-avian" if it has feathers?  Don't feathers imply flight, and therefore avian status?

Avatar of:

Posts: 0

July 28, 2011

What makes Archaeopteryx "non-avian" if it has feathers?  Don't feathers imply flight, and therefore avian status?

Avatar of:

Posts: 0

July 28, 2011

Arrrggghhhh............the R word repltile/reptilian was used. They were not reptiles they were dinosaurs, an important distinction as there is overwhelming evidence they were warm blooded (endothermic) just like mammals and the birds derived from them through evolution.

Avatar of:

Posts: 0

July 28, 2011

What makes Archaeopteryx "non-avian" if it has feathers?  Don't feathers imply flight, and therefore avian status?

Avatar of:

Posts: 0

July 29, 2011

A lot of dinosaurs had feathers but were dinosaurs not birds. Birds have a distinct keel on their strenum and a well developed 'wishbone'. Without the keel for muscle attachments you would expect only gliding flight for the very early 'birds' as opposed to flapping flight. It seems that aerodynamic feathers may predate actual flapping flight but may have developed initially for gliding.

Avatar of:

Posts: 0

July 29, 2011

the right word is "homeothermic", I think endothermic is restricted to heat absorbing chemical reaction! is not it.
I welcome comments to rectify me, if i am wrong.

Avatar of:

Posts: 0

July 29, 2011

from the
Encyclopædia Britannica

Get involved
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<script

src="http://adserver.adtechus.com/a..."></script>
endotherm, so-called warm-blooded animals; that is, those that maintain a constant body temperature independent of the environment. The endotherms primarily include the birds and mammals;
however, some fish are also endothermic. If heat loss exceeds heat
generation, metabolism increases to make up the loss or the animal
shivers to raise its body temperature. If heat generation exceeds the
heat loss, mechanisms such as panting or perspiring increase heat loss.
Unlike ectotherms, endotherms can be active and survive at quite low external temperatures, but because they must produce heat continuously, they require high quantities of “fuelâ€쳌 (i.e., food).

Avatar of:

Posts: 0

July 29, 2011

I did post a reply from the Encyclopaedia Brittanica which says I used the term endotherm correctly but this site has a problem with it probably owing to links within it.

Avatar of:

Posts: 0

July 29, 2011

Archaeopteryx may not after all be the first bird but it was the first bird-like animal to be found in the fossil record, and its discovery helped establish an evolutionary link between dinosaurs and modern birds. Furthermore, the timimg was propitious - within 2 years of publication of Darwin's Origin of Species. Archaeopteryx is iconic, and always will be, regardless of where it ends up in the tree of life.

Avatar of:

Posts: 0

July 29, 2011

A lot of dinosaurs had feathers but were dinosaurs not birds. Birds have a distinct keel on their strenum and a well developed 'wishbone'. Without the keel for muscle attachments you would expect only gliding flight for the very early 'birds' as opposed to flapping flight. It seems that aerodynamic feathers may predate actual flapping flight but may have developed initially for gliding.

Avatar of: Chalcedon

Chalcedon

Posts: 4

July 29, 2011

A lot of dinosaurs had feathers but were dinosaurs not birds. Birds have a distinct keel on their strenum and a well developed 'wishbone'. Without the keel for muscle attachments you would expect only gliding flight for the very early 'birds' as opposed to flapping flight. It seems that aerodynamic feathers may predate actual flapping flight but may have developed initially for gliding.

Avatar of:

Posts: 0

July 29, 2011

the right word is "homeothermic", I think endothermic is restricted to heat absorbing chemical reaction! is not it.
I welcome comments to rectify me, if i am wrong.

Avatar of:

Posts: 0

July 29, 2011

from the
Encyclopædia Britannica

Get involved
Share

<script

src="http://adserver.adtechus.com/a..."></script>
endotherm, so-called warm-blooded animals; that is, those that maintain a constant body temperature independent of the environment. The endotherms primarily include the birds and mammals;
however, some fish are also endothermic. If heat loss exceeds heat
generation, metabolism increases to make up the loss or the animal
shivers to raise its body temperature. If heat generation exceeds the
heat loss, mechanisms such as panting or perspiring increase heat loss.
Unlike ectotherms, endotherms can be active and survive at quite low external temperatures, but because they must produce heat continuously, they require high quantities of “fuelâ€쳌 (i.e., food).

Avatar of:

Posts: 0

July 29, 2011

I did post a reply from the Encyclopaedia Brittanica which says I used the term endotherm correctly but this site has a problem with it probably owing to links within it.

Avatar of:

Posts: 0

July 29, 2011

Archaeopteryx may not after all be the first bird but it was the first bird-like animal to be found in the fossil record, and its discovery helped establish an evolutionary link between dinosaurs and modern birds. Furthermore, the timimg was propitious - within 2 years of publication of Darwin's Origin of Species. Archaeopteryx is iconic, and always will be, regardless of where it ends up in the tree of life.

Avatar of: C S Mukhopadhyay

Anonymous

July 29, 2011

the right word is "homeothermic", I think endothermic is restricted to heat absorbing chemical reaction! is not it.
I welcome comments to rectify me, if i am wrong.

Avatar of: Chalcedon

Chalcedon

Posts: 4

July 29, 2011

from the
Encyclopædia Britannica

Get involved
Share

<script

src="http://adserver.adtechus.com/a..."></script>
endotherm, so-called warm-blooded animals; that is, those that maintain a constant body temperature independent of the environment. The endotherms primarily include the birds and mammals;
however, some fish are also endothermic. If heat loss exceeds heat
generation, metabolism increases to make up the loss or the animal
shivers to raise its body temperature. If heat generation exceeds the
heat loss, mechanisms such as panting or perspiring increase heat loss.
Unlike ectotherms, endotherms can be active and survive at quite low external temperatures, but because they must produce heat continuously, they require high quantities of “fuelâ€쳌 (i.e., food).

Avatar of: Chalcedon

Chalcedon

Posts: 4

July 29, 2011

I did post a reply from the Encyclopaedia Brittanica which says I used the term endotherm correctly but this site has a problem with it probably owing to links within it.

Avatar of: Michael Morris

Anonymous

July 29, 2011

Archaeopteryx may not after all be the first bird but it was the first bird-like animal to be found in the fossil record, and its discovery helped establish an evolutionary link between dinosaurs and modern birds. Furthermore, the timimg was propitious - within 2 years of publication of Darwin's Origin of Species. Archaeopteryx is iconic, and always will be, regardless of where it ends up in the tree of life.

Avatar of: Alexandru Boris Cosciug

Anonymous

July 31, 2011

Disappearance
missing links in EVOLUTION to go a long way until homo sapiens (wise man)

Charles Robert Darwin
was the first "wise man"
that starts the scientific explanation of the life evolution.

What a pity that the
Bibles performers do not comprehend the Bible!

*Four huge beasts came up out of the ocean, each one different from the
others. The first one looked like a lion, but had wings like eagle. While I was
watching, the wings were torn off. The beast was lifted up and made to stand like
a man. And then a human mind was given to it.* (Daniel 7. 3-4)

But, before *the end of the world, meanwhile, many people
will waste the efforts trying to understand what is happening.* (Daniel
12.4)

*We honour God for what he conceals; we honour kings for what they
explain.* (Solomon's Proverbs - 25.2)

What a chance the *TheScientist* exist and many *kings can scientifically explain the life evolution*!

 

Avatar of:

Posts: 0

July 31, 2011

Disappearance
missing links in EVOLUTION to go a long way until homo sapiens (wise man)

Charles Robert Darwin
was the first "wise man"
that starts the scientific explanation of the life evolution.

What a pity that the
Bibles performers do not comprehend the Bible!

*Four huge beasts came up out of the ocean, each one different from the
others. The first one looked like a lion, but had wings like eagle. While I was
watching, the wings were torn off. The beast was lifted up and made to stand like
a man. And then a human mind was given to it.* (Daniel 7. 3-4)

But, before *the end of the world, meanwhile, many people
will waste the efforts trying to understand what is happening.* (Daniel
12.4)

*We honour God for what he conceals; we honour kings for what they
explain.* (Solomon's Proverbs - 25.2)

What a chance the *TheScientist* exist and many *kings can scientifically explain the life evolution*!

 

Avatar of:

Posts: 0

July 31, 2011

Disappearance
missing links in EVOLUTION to go a long way until homo sapiens (wise man)

Charles Robert Darwin
was the first "wise man"
that starts the scientific explanation of the life evolution.

What a pity that the
Bibles performers do not comprehend the Bible!

*Four huge beasts came up out of the ocean, each one different from the
others. The first one looked like a lion, but had wings like eagle. While I was
watching, the wings were torn off. The beast was lifted up and made to stand like
a man. And then a human mind was given to it.* (Daniel 7. 3-4)

But, before *the end of the world, meanwhile, many people
will waste the efforts trying to understand what is happening.* (Daniel
12.4)

*We honour God for what he conceals; we honour kings for what they
explain.* (Solomon's Proverbs - 25.2)

What a chance the *TheScientist* exist and many *kings can scientifically explain the life evolution*!

 

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