How birds got their wings

Frank Robert · Feb 24, 2023

A branch of the tree of life that includes the time when the propatagium, vital to flight in future birds, came about.

"Modern birds capable of flight all have a specialized wing structure called the propatagium without which they could not fly. The evolutionary origin of this structure has remained a mystery, but new research suggests it evolved in nonavian dinosaurs. The finding comes from statistical analyses of arm joints preserved in fossils and helps fill some gaps in knowledge about the origin of bird flight.

For a long time now, we have known modern birds evolved from certain lineages of dinosaurs that lived millions of years ago. This has led researchers to look to dinosaurs to explain some of the features unique to birds, for example, feathers, bone structure and so on. But there's something special about the wings of birds in particular that piqued the interest of researchers at the University of Tokyo's Department of Earth and Planetary Science."

"At the leading edge of a bird's wing is a structure called the propatagium, which contains a muscle connecting the shoulder and wrist that helps the wing flapping and makes bird flight possible," said Associate Professor Tatsuya Hirasawa.

"It's not found in other vertebrates, and it's also found to have disappeared or lost its function in flightless birds, one of the reasons we know it's essential for flight. So, in order to understand how flight evolved in birds, we must know how the propatagium evolved. This is what prompted us to explore some distant ancestors of modern birds, theropod dinosaurs."

Read more...

AV1611VET · Feb 25, 2023

Only on paper.

Frank Robert · Feb 25, 2023

AV1611VET said:
Only on paper.

You must have missed the physical evidence connecting propatagium in fossils of certain dionsaurs and wing joints of all birds except those who have lost the ability for flight. You can falsify the theory by finding flying birds w/o a propatagium.

Ophiolite · Feb 26, 2023

Frank Robert said:
You can falsify the theory by finding flying birds w/o a propatagium.

They're out there Frank. I've seen 'em. Trouble is when I creep up on them the pesky rascals just fly away! What more proof do you need?

The Barbarian · May 25, 2025

Frank Robert said:
"Modern birds capable of flight all have a specialized wing structure called the propatagium without which they could not fly.

The killer question for those denying that birds are dinosaurs is "What feature found in birds, is not also found in at least some dinosaurs?" And now, it seem that this feature isn't going to be the magic bullet, either.

The Barbarian · May 27, 2025

It seems that the propatagium was preadapted to flight, having evolved before flying dinosaurs evolved. What Gould referred to as a "spandrel", a phenotypic feature that is a byproduct of the evolution of some other characteristic, rather than a direct product of adaptive selection.

Our analyses support the hypothesis that the preserved propatagium-like soft tissues in non-avian theropod dinosaurs (oviraptorosaurian Caudipteryx and dromaeosaurian Microraptor) are homologous with the avian propatagium, and indicate that all maniraptoran dinosaurs likely possessed the propatagium even before the origin of flight. On the other hand, the preserved angles of wrist joints in non-avian theropods are significantly greater than those in birds, suggesting that the avian interlocking wing-folding mechanism involving the ulna and radius had not fully evolved in non-avian theropods. Our study underscores that the avian wing was acquired through modifications of preexisting structures including the feather and propatagium.

Origin of the propatagium in non-avian dinosaurs - Zoological Letters

Avian wings as organs for aerial locomotion are furnished with a highly specialized musculoskeletal system compared with the forelimbs of other tetrapod vertebrates. Among the specializations, the propatagium, which accompanies a skeletal muscle spanning between the shoulder and wrist on the...

zoologicalletters.biomedcentral.com

AACJ · Wednesday at 4:30 AM

Frank Robert said:
View attachment 328403
A branch of the tree of life that includes the time when the propatagium, vital to flight in future birds, came about.

"Modern birds capable of flight all have a specialized wing structure called the propatagium without which they could not fly. The evolutionary origin of this structure has remained a mystery, but new research suggests it evolved in nonavian dinosaurs. The finding comes from statistical analyses of arm joints preserved in fossils and helps fill some gaps in knowledge about the origin of bird flight.

For a long time now, we have known modern birds evolved from certain lineages of dinosaurs that lived millions of years ago. This has led researchers to look to dinosaurs to explain some of the features unique to birds, for example, feathers, bone structure and so on. But there's something special about the wings of birds in particular that piqued the interest of researchers at the University of Tokyo's Department of Earth and Planetary Science."

"At the leading edge of a bird's wing is a structure called the propatagium, which contains a muscle connecting the shoulder and wrist that helps the wing flapping and makes bird flight possible," said Associate Professor Tatsuya Hirasawa.

"It's not found in other vertebrates, and it's also found to have disappeared or lost its function in flightless birds, one of the reasons we know it's essential for flight. So, in order to understand how flight evolved in birds, we must know how the propatagium evolved. This is what prompted us to explore some distant ancestors of modern birds, theropod dinosaurs."

Read more...

The claim that the propatagium evolved in non-avian dinosaurs is built on inference, not on direct evidence. There are no transitional fossils that show a gradual development of the propatagium; rather, the structure appears fully formed in birds, with no functional intermediates documented (Ostrom, "Archaeopteryx and the Origin of Flight"; Feduccia, "Riddle of the Feathered Dragons"). Also, soft tissue like the propatagium rarely fossilizes, which makes such evolutionary claims speculative at best (Benton, "Vertebrate Paleontology").

The sudden appearance of birds capable of flight in the fossil record remains unexplained by gradualistic evolution.

References:

John H. Ostrom, "Archaeopteryx and the Origin of Flight"

Alan Feduccia, "Riddle of the Feathered Dragons: Expeditions on the Trail of Prehistoric Birds"

Michael J. Benton, "Vertebrate Paleontology"

Ophiolite · Wednesday at 5:52 AM

AACJ said:
The claim that the propatagium evolved in non-avian dinosaurs is built on inference, not on direct evidence.

What would you consider to be direct evidence?

What, precisely, is your objection to the use of inference in developing a hypothesis? (I'm a simple minded chap, with no post graduate degrees. Please keep the epistemological jargon to a minimum in your reply.)

Larniavc · Wednesday at 7:02 AM

AACJ said:
The claim that the propatagium evolved in non-avian dinosaurs is built on inference, not on direct evidence. There are no transitional fossils that show a gradual development of the propatagium; rather, the structure appears fully formed in birds, with no functional intermediates documented (Ostrom, "Archaeopteryx and the Origin of Flight"; Feduccia, "Riddle of the Feathered Dragons"). Also, soft tissue like the propatagium rarely fossilizes, which makes such evolutionary claims speculative at best (Benton, "Vertebrate Paleontology").

The sudden appearance of birds capable of flight in the fossil record remains unexplained by gradualistic evolution.

References:

John H. Ostrom, "Archaeopteryx and the Origin of Flight"

Alan Feduccia, "Riddle of the Feathered Dragons: Expeditions on the Trail of Prehistoric Birds"

Michael J. Benton, "Vertebrate Paleontology"

Archaeopteryx and the origin of birds
JOHN H. OSTROM

First published: June 1976

"All available evidence indicates unequivocally that Archaeopteryx evolved from a small coelurosaurian dinosaur and that modern birds are surviving dinosaurian descendants. Stated simply, avian phylogeny was: Pseudosuchia Coelurosauria Archaeopteryx higher birds."

The Barbarian · Wednesday at 8:00 AM

AACJ said:
The claim that the propatagium evolved in non-avian dinosaurs is built on inference, not on direct evidence.

The evidence that exists, as you learned, points to the evolution of ot propatagium in pre-avian dinosaurs. The key is where flapping motion began. Maniraptoran dinosaurs were running bipedal animals, mostly predators. And there is considerable evidence for the sort of folding that would require a propatiagium:

Proceedings of the Royal Society 03 March 2010

The asymmetry of the carpal joint and the evolution of wing folding in maniraptoran theropod dinosaurs

Abstract

In extant birds, the hand is permanently abducted towards the ulna, and the wrist joint can bend extensively in this direction to fold the wing when not in use. Anatomically, this asymmetric mobility of the wrist results from the wedge-like shape of one carpal bone, the radiale, and from the well-developed convexity of the trochlea at the proximal end of the carpometacarpus. Among the theropod precursors of birds, a strongly convex trochlea is characteristic of Coelurosauria, a clade including the highly derived Maniraptora in addition to tyrannosaurs and compsognathids. The shape of the radiale can be quantified using a ‘radiale angle’ between the proximal and distal articular surfaces. Measurement of the radiale angle and reconstruction of ancestral states using squared-change parsimony shows that the angle was small (15°) in primitive coelurosaurs but considerably larger (25°) in primitive maniraptorans, indicating that the radiale was more wedge-shaped and the carpal joint more asymmetric. The radiale angle progressively increased still further within Maniraptora, with concurrent elongation of the forelimb feathers and the forelimb itself. Carpal asymmetry would have permitted avian-like folding of the forelimb in order to protect the plumage, an early advantage of the flexible, asymmetric wrist inherited by birds.

It probably seemed like a lucky break for YECs that there wasn't an example of soft tissue fossilizing in this case. YECs probably never realized that there isn't direct fossil evidence for the propataium in fossil birds, either. They stacked all their hopes on something that's not there, never realizing that hard tissues that do fossilize, provide evidence for it, in non-avian maniraptoran dinosaurs. Absence of evidence is not evidence of absence.

AACJ said:
The sudden appearance of birds capable of flight in the fossil record remains unexplained by gradualistic evolution.

Fact is, there were non-avian dinosaurs like Archaeopteryx, which were capable of flight. It's not a sudden appearance.

Archaeopteryx, though definitely bird-like, falls outside the modern bird group.
“Although you can’t unambiguously call Archaeopteryx a bird, it is unambiguously a dinosaur,” says Daniel.
“As it had some features that we see in modern birds, but others that were much more dinosaur-like, I’m uneasy about calling Archaeopteryx a bird. But it’s getting close!”

What were the first birds like? | Natural History Museum

Find out when the first birds appeared, what they looked like and how they behaved. Learn about the wonderchicken, as well as the earliest bird-like animals such as Archaeopteryx and Anchiornis.

www.nhm.ac.uk

AACJ said:
The sudden appearance of birds capable of flight in the fossil record remains unexplained by gradualistic evolution.

Looks rather gradual when you see the evidence displayed.

How birds got their wings

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Archaeopteryx and the origin of birds JOHN H. OSTROM​

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Proceedings of the Royal Society 03 March 2010​

The asymmetry of the carpal joint and the evolution of wing folding in maniraptoran theropod dinosaurs​

Abstract​

Similar threads

Archaeopteryx and the origin of birds
JOHN H. OSTROM

Proceedings of the Royal Society 03 March 2010

The asymmetry of the carpal joint and the evolution of wing folding in maniraptoran theropod dinosaurs

Abstract