Feathers Came First Then Birds Evolved

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Feathers Came First Then Birds Evolved

With the discovery of the amazing feathered dinosaur fossils from China, scientists have had to re-think their views about the appearance of dinosaurs, but the story of the evolution of the feather goes more than just skin deep.  In a follow up, to an earlier scientific paper published late last year that examined the evidence for four different types of feather in the Pterosauria, a team of researchers have concluded that the feather arose around 80 million years earlier than the first bird.  Furthermore, the study, led by scientists at the University of Bristol proposes that feathers played a significant role in helping to shape modern terrestrial ecosystems.

Not Just a Flight of Fancy – Feathers Change the Way We Look at Archosaurs

A fossilised feather from the Crato Formation

Numerous isolated feathers have been preserved indicating the presence of Avialae – primitive birds and theropod dinosaurs closely related to birds.  In addition, feather-like structures have been identified in pterosaurs.

Picture Credit: Museu Nacional

Changing Our Understanding of Feathers, Their Function and Role in Evolution

Writing in the academic journal “Trends in Ecology and Evolution”, the researchers develop the work undertaken last year that looked at evidence for feathers in flying reptile fossils from China and utilises techniques deployed in molecular biology to plot the development of integumentary producing genes within the Archosauria.  If feathers did evolve in the Pterosauria as well as the Dinosauria, then this suggests that their common ancestor may have been feathered to.  Feather-like structures probably arose relatively early in the evolution of the Archosaurs.

Lead author of the paper, Professor Mike Benton (Bristol University), commented:

“The oldest bird is still Archaeopteryx first found in the Late Jurassic of southern Germany in 1861, although some species from China are a little older.  Those fossils all show a diversity of feathers – down feathers over the body and long, vaned feathers on the wings.  But, since 1994, palaeontologists have been contending with the perturbing discovery, based on hundreds of amazing specimens from China, that many dinosaurs also had feathers.”

Archaeopteryx – An Early Bird But Not The First Creature to Have Feathers

An illustration of Archaeopteryx.

The first bird – “Urvogel”, the Archaeopteryx but not the first animal to have feathers.

Picture Credit: Carl Buell

Links Between Fish Teeth, Scales, Feathers and Mammalian Hair

Feathers are modified epidermal appendages that consist mainly of horn-like proteins (β-proteins).  Research has identified links at the genetic level between structures in vertebrates associated with shark teeth, dermal scales in teleost fishes, reptilian scales, feathers and mammalian body hair.  The discovery that genes specific to the production of feathers evolved at the base of the Archosauria clade rather than in association with stem members of the Avialae (birds), is supported by fossil evidence in the form of numerous examples of feathered dinosaurs including examples of feathers in Ornithischian dinosaurs as well as the Theropoda.  Many of the authors of this new paper also worked on the study into feathers in pterosaurs published in December last year.

A Genetic Link Between Dermal Coverings in Tetrapods and Teleost Fish Scales

Looking at the orgins of feathers, a link established between integumentary coverings and fish scales.

Fish scales linked to feathers in genome analysis.

Picture Credit: Everything Dinosaur

If feathers evolved before the evolution of flight, they probably arose first as simple monofilament structures most likely to aid the retention of body heat in the archosaurian ancestors of birds and dinosaurs, perhaps first appearing sometime in the Early Triassic, a time after the Permian mass extinction which had led to a massive terrestrial faunal turnover and the evolution of more active animals with upright, erect gaits.

Co-author of the study, Baoyu Jiang from the University of Nanjing (China), added:

“At first, the dinosaurs with feathers were close to the origin of birds in the evolutionary tree.  This was not so hard to believe.  So, the origin of feathers was pushed back at least to the origin of those bird-like dinosaurs, maybe 200 million years ago.  In fact, we have shown that the same genome regulatory network drives the development of reptile scales, bird feathers, and mammal hairs.  Feathers could have evolved very early.”

Pterosaurs Had Feathers

The breakthrough for the research team occurred when two new types of pterosaur from China were studied.  Their pycnofibres showed branching, they did not have monofilaments but tufts and downy-like feathers, this led to the conclusion that members of the Pterosauria had feathers too.

Baoyu Jiang continued: “The breakthrough came when we were studying two new pterosaurs from China.

Professor Benton postulated that this area of research indicates the origins of feathers some 250 million years ago.

The professor explained:

“The point of origin of pterosaurs, dinosaurs and their relatives.  The Early Triassic world then was recovering from the most devastating mass extinction ever, and life on land had come back from near-total wipe-out.  Palaeontologists had already noted that the new reptiles walked upright instead of sprawling, that their bone structure suggested fast growth and maybe even warm-bloodedness, and the mammal ancestors probably had hair by then.  So, the dinosaurs, pterosaurs and their ancestors had feathers too.  Feathers then probably arose to aid this speeding up of physiology and ecology, purely for insulation.  The other functions of feathers, for display and of course for flight, came much later.”

The Importance of Kulindadromeus

Co-author Dr Maria McNamara (University College Cork, Ireland), explained that the discovery of a feathered dinosaur not thought to be closely related to birds has changed the way some palaeontologists view the evolution of feathers.  In 2014, a formal paper was published on a small, bird-hipped dinosaur that was named Kulindadromeus.  Fossils of this small, Siberian herbivore showed that it had skin covered with scales on the legs and tail, but strange, feathery filaments over much of the rest of its body.

The article announcing the discovery of feathers on an Ornithischian dinosaur: Did All Dinosaurs Have Feathers?

A Scale Model of the Feathered Ornithischian Dinosaur Kulindadromeus (K. zabaikalicus)

A scale model of the feathered dinosaur Kulindadromeus.

A 1:1 scale model of Kulindadromeus (Kulindadromeus zabaikalicus)

Picture Credit: T. Hubin/RBINS

Dr McNamara commented:

“What surprised people was that this was a dinosaur that was as far from birds in the evolutionary tree as could be imagined.  Perhaps feathers were present in the very first dinosaurs.”

Fellow co-author Danielle Dhouailly (University of Grenoble, France), studies the development of feathers in baby birds, especially their genomic control.  Her research has demonstrated that modern birds such as chickens often have scales on their legs or necks, these are in fact evidence of reversal, what had once been feathers had reverted to their more ancient form, that of reptilian scales.

This research supports the idea that gene regulatory networks show that the development of scales, feathers and hairs are co-ordinated by a similar set of genes.  Feathers and body hair probably evolved in the Early Triassic with the ancestors of mammals and birds, at a time when synapsids (the lineage of tetrapods that led to mammals) and archosaurs (dinosaurs and birds), show independent evidence of higher metabolic rates.  It was the mass extinction event at the end of the Permian that re-set the evolutionary clock and permitted the evolution of more active land animals, setting terrestrial lifeforms on a course that would ultimately lead to the rise of the dinosaur, volant flight in the Dinosauria and of course the evolution of modern mammals including ourselves.

The scientific paper: “The Early Origin of Feathers” by M. J. Benton, D. Dhouailly, B. Jiang and M. McNamara published in Trends in Ecology & Evolution.

To read our earlier article (December 2018) that examined the evidence for four different kinds of feather-like structures associated with pterosaur fossils: Are the Feathers About to Fly in the Pterosauria?

To read an article from 2015 setting out a counter argument concluding that the majority of the Dinosauria probably did not have feathers: Most Dinosaurs Were Probably Scaly.