‘Dinosaurs Among Us’ Retraces an Evolutionary Path

Mar 30, 2016

Photo credit: Zhao Chuang/Peking Natural Science Organization

By John Noble Wilford

At a preview of the new American Museum of Natural History exhibition “Dinosaurs Among Us,” scientists gave a tip of the hat to Thomas Henry Huxley, the man who proposed in the 1860s that dinosaurs never really vanished from Earth. Most did go extinct, but their evolutionary legacy lives all around us. They are birds, all 18,000 species of them.

While Charles Darwin’s book of books, “On the Origin of Species by Means of Natural Selection,” was still in print in 1859, Huxley, a lecturer in paleontology and natural history in London, wrote a favorable review and became a convert to Darwin’s theory. In a debate the next year, Huxley got the better of the bishop of Oxford, and became known thereafter as Darwin’s bulldog. He was also the first in a long line of Huxleys who distinguished themselves in science and the arts.

A few years later, Huxley enlisted Archaeopteryx, a fossil specimen found in a Bavarian limestone quarry, in his defense of Darwin. He was struck by the specimen’s many reptilian features; but for a feather in the fossil, it would probably have been misidentified as a reptile. In a report in 1867, Huxley established the evolutionary relationship of birds and reptiles, citing 14 anatomical features that occur in birds and reptiles alike, but not in mammals.

Archaeopteryx was one of those “missing links” in the fossil record that Darwin worried was a weakness in this theory of evolution. Huxley called attention to the feathers and wishbone of this early bird and the long bony tail of a reptile. This was a species in transition.

Why has it taken so long to recognize that Huxley had almost certainly been right about the origin of birds from some meat-eating theropod dinosaurs?

Mark A. Norell, the chairman of the division of paleontology at A.M.N.H. and curator of the exhibition, had long been a staunch proponent of a dinosaur-bird link. A lot of evidence amassed over the last two decades, especially the numbers of feathered dinosaurs found in China, moved paleontologists to organize the exhibition as a kind of victory lap.

“I think this is really going to shake up the way people think of dinosaurs,” Dr. Norell said.


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9 comments on “‘Dinosaurs Among Us’ Retraces an Evolutionary Path

  • @OP – Mark A. Norell, the chairman of the division of paleontology at A.M.N.H. and curator of the exhibition, had long been a staunch proponent of a dinosaur-bird link. A lot of evidence amassed over the last two decades, especially the numbers of feathered dinosaurs found in China, moved paleontologists to organize the exhibition as a kind of victory lap.

    There has certainly been a clear view of this relationship among palaeontologists and biologists for a long time.

    This national geographic link has been posted on RDFS before.

    http://ngm.nationalgeographic.com/2011/02/feathers/zimmer-text

    “I think this is really going to shake up the way people think of dinosaurs,” Dr. Norell said.

    There are still many members of the wider public, who need educating to understand this evolutionary connection.



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  • I have a question about the evolution of long feathers on the birds wing.

    When primitives birds start to fly was their wing covered with short feathers or long feather ?

    I mean is it possible that the feather didn’t play any role in flying of the primitive birds and they were flying like bats without having any long feather on their wing ?

    Then evolution kicks in an gives advantage to longer feather on the birds wings because longer feather can maintain the surface area of wing with less flesh and skin. And with less flesh and skin and longer feathers they could save some energy during flight. Because live tissue consumes more energy comparing to feather that is mainly maid of dead tissue.

    Is there any evidence that confirms or rejects this theory ?



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  • peyman #3
    Apr 2, 2016 at 5:25 pm

    I have a question about the evolution of long feathers on the birds wing.

    When primitives birds start to fly was their wing covered with short feathers or long feather ?

    The evidence is that bird ancestors had feathers and feathers on limbs, long before they evolved the ability to glide and then to fly.
    These appear to be for display, helping balance, protection from the weather etc.

    I mean is it possible that the feather didn’t play any role in flying of the primitive birds and they were flying like bats without having any long feather on their wing ?

    There is no evidence that bird ancestors flew like bats with naked wing membranes.
    Pterosaurs did, but they were not bird ancestors.

    My National geographic link @#1 has some details, with other information on this link.

    http://evolution.berkeley.edu/evolibrary/article/evograms_06

    The early feathers were placodes, simple downy feathers, and feathers with central stalks. The specialist flight feathers only evolved later, as gliding and flight developed.



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  • There’s an even more astonishing possibility. The closest living
    relatives of birds, dinosaurs, and pterosaurs are crocodilians.
    Although these scaly beasts obviously do not have feathers today, the
    discovery of the same gene in alligators that is involved in building
    feathers in birds suggests that perhaps their ancestors did, 250
    million years ago, before the lineages diverged. So perhaps the
    question to ask, say some scientists, is not how birds got their
    feathers, but how alligators lost theirs

    http://ngm.nationalgeographic.com/print/2011/02/feathers/zimmer-text
    .



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  • @ Alan

    This might answer the question posed in my post #5.

    But even though we think of them as ‘cold-blooded’, ectothermic
    animals can still have warm blood. And the bigger they are, the more
    likely they are to be able to maintain a warm body temperature.

    Smaller animals will need a way of keeping in the heat whether ectothermic or endothermic. The display qualities being part of the process with warm bodies better to incubate eggs in cold whether as we see with the Emperor penguins whose eggs will freeze in seconds if left alone.



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  • Olgun #7
    Apr 2, 2016 at 7:36 pm

    Smaller animals will need a way of keeping in the heat whether ectothermic or endothermic.

    There is also the factor that if the body becomes chilled and torpid, a flying bird hitting a patch of cold air, will drop out of the sky!

    Also following the KT extinction, the climate flip-flopped about with some very cold periods.



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  • There is a hypothesis here on why birds survived the KT extinction.

    http://www.bbc.co.uk/news/science-environment-36102018

    Modern birds owe their survival to ancestors who were able to peck on seeds after the meteor that wiped out most dinosaurs, say scientists.

    Bird-like dinosaurs with toothless beaks survived the “nuclear winter” that followed the meteor strike, because of their diet, a study says.

    The impact altered the climate of the Earth and blotted out sunlight.

    The loss of vegetation would have deprived plant-eating dinosaurs of food. In turn, meat-eaters suffered.

    But seeds still in the ground may have sustained small toothless bird ancestors until the planet began to recover.

    The theory, outlined in the journal Current Biology, could explain why no modern bird has a beak lined with teeth.

    “After this meteor, you’re left with essentially a nuclear winter where really not much is growing, the plants aren’t able to grow to provide nourishment for plant-eaters and then meat-eaters aren’t able to access plant-eaters if they’ve all perished,” said lead researcher Derek Larson, from the University of Toronto.

    “We think that the survival of birds had something to do with the presence of their beak.”

    The researchers studied more than 3,000 fossilised teeth from bird-like dinosaurs known as maniraptorans.

    These dinosaurs are some of the closest relatives of modern birds – but, at the end of the Cretaceous period, many disappeared, including the toothed birds.

    The team suspected diet might have played a part in the survival of the ancestors of modern birds.

    “We came up with a hypothesis that it had something to do with diet,” Mr Larson said.

    “Looking at the diet of modern birds, we were able to reconstruct a hypothetical ancestral bird and what its likely diet would have been,” he told the BBC’s Science in Action programme.

    “What we’re envisaging is a seed-eating bird, so you’d have a relatively short and robust strong beak, which would be able to crush these seeds.”

    Mr Larson said most of today’s birds would not be around if it were not for their seed-eating ancestors, although a handful of other birds might have survived the impact, perhaps through eating insects.

    “We might be looking at a very different picture of bird diversity had certain groups not evolved the ability to eat seed material,” he said.

    The dust in the atmosphere from the strike of the huge comet or asteroid would have obscured sunlight and blocked photosynthesis.

    However, seeds that had already built up in the ground would have still been available as a food source for anything with a beak capable of eating them.



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