Photo 27 Feb 507 notes Giant Prehistoric Bird Crushed Seeds, Not Little Horses

While not so huge as the largest non-avian dinosaurs, Gastornis was nevertheless a giant in its Paleocene and Eocene heyday between 55 and 40 million years ago. In Europe the bird towered over the mammals who inhabited the same forests – the largest herbivores and carnivores of the day were about the size of a German shepherd, with many being considerably smaller. (In North America, where Gastornis fossils were previously labeled “Diatryma“, some of the contemporary herbivorous mammals grew to bigger sizes, but there were still many smaller beasts running about.) So it seemed only natural that the monstrous bird would have preyed on the scurrying mammals, pouncing on “dawn horses” and cleaving lemur-like primates in two with it’s powerful beak. In museums and documentaries, Gastornis marked the last gasp of dinosaur dominance before mammals took over the world.
But recent research has found that Gastornis wasn’t so terrifying, after all. While a 1991 paper concluded that the bird’s beak could have made short work of many small mammals, other publications pointed out that such a beak would have been just as well-suited to cracking seeds and crunching tough fruit. More recently, tracks of Gastornis – née “Diatryma” – found in Washington show that the bird had blunted toes rather than vicious talons, and a preliminary study of dietary clues preserved in the bones of a German specimen of the bird suggested a menu of plants rather than flesh. And now paleontologist Delphine Angst and colleagues have added another line of evidence that Gastornis probably wasn’t a rapacious mammal-muncher.
Chemical signatures in the extinct bird’s bones are at the center of the Naturwissenschaften study. Angst and coauthors studied carbon isotope (δ13C) traces in the bones of Gastornis, small herbivorous mammals the bird lived alongside, and modern hawks and ostriches. This isotope acts as a proxy for diet. Generated inside plants, the carbon isotope becomes preserved in the tissues of herbivores that eat those greens and, further down the line, in the tissues of the carnivores that consume those herbivores. Locked in bones and teeth, this carbon isotope allows paleontologists to outline what individual animals were consuming and how they may have split up resources in the same habitat….
When Angst and coauthors looked at the carbon isotope through the lens of Gastornis being an herbivore, however, the signature was a better match and was comparable to those of herbivorous mammals living at the same time. The bird’s carbon isotope profile was that of an avian that crushed seeds and crunched thick-skinned fruit.
And the researchers went a step further. Through dissections of modern birds ranging from Darwin’s finches to Eurasian sparrowhawks, Angst and colleagues studied the anatomy and connection points of the external adductor muscle in modern herbivorous and carnivorous birds. This is a major muscle that powers bird bites, and the herbivorous, seed-cracking birds typically had wider muscles with increased space for attachment on the lower jaw. That fits they way they feed. Much more power is needed to bust open hard fruits than to tear soft flesh.
The actual muscles of Gastornis rotted away over 40 million years ago, but the bird’s lower jaw shows a wide space for the external adductor muscle to attach. Taken together, the bird’s beak, feet, reconstructed musculature, and chemical signature best fit a large herbivore that snacked on plants rather than the mammals that lived underfoot.

(Read more at Phenomena: Laelaps)

Giant Prehistoric Bird Crushed Seeds, Not Little Horses

While not so huge as the largest non-avian dinosaurs, Gastornis was nevertheless a giant in its Paleocene and Eocene heyday between 55 and 40 million years ago. In Europe the bird towered over the mammals who inhabited the same forests – the largest herbivores and carnivores of the day were about the size of a German shepherd, with many being considerably smaller. (In North America, where Gastornis fossils were previously labeled “Diatryma“, some of the contemporary herbivorous mammals grew to bigger sizes, but there were still many smaller beasts running about.) So it seemed only natural that the monstrous bird would have preyed on the scurrying mammals, pouncing on “dawn horses” and cleaving lemur-like primates in two with it’s powerful beak. In museums and documentaries, Gastornis marked the last gasp of dinosaur dominance before mammals took over the world.

But recent research has found that Gastornis wasn’t so terrifying, after all. While a 1991 paper concluded that the bird’s beak could have made short work of many small mammals, other publications pointed out that such a beak would have been just as well-suited to cracking seeds and crunching tough fruit. More recently, tracks of Gastornis – née “Diatryma” – found in Washington show that the bird had blunted toes rather than vicious talons, and a preliminary study of dietary clues preserved in the bones of a German specimen of the bird suggested a menu of plants rather than flesh. And now paleontologist Delphine Angst and colleagues have added another line of evidence that Gastornis probably wasn’t a rapacious mammal-muncher.

Chemical signatures in the extinct bird’s bones are at the center of the Naturwissenschaften study. Angst and coauthors studied carbon isotope (δ13C) traces in the bones of Gastornis, small herbivorous mammals the bird lived alongside, and modern hawks and ostriches. This isotope acts as a proxy for diet. Generated inside plants, the carbon isotope becomes preserved in the tissues of herbivores that eat those greens and, further down the line, in the tissues of the carnivores that consume those herbivores. Locked in bones and teeth, this carbon isotope allows paleontologists to outline what individual animals were consuming and how they may have split up resources in the same habitat….

When Angst and coauthors looked at the carbon isotope through the lens of Gastornis being an herbivore, however, the signature was a better match and was comparable to those of herbivorous mammals living at the same time. The bird’s carbon isotope profile was that of an avian that crushed seeds and crunched thick-skinned fruit.

And the researchers went a step further. Through dissections of modern birds ranging from Darwin’s finches to Eurasian sparrowhawks, Angst and colleagues studied the anatomy and connection points of the external adductor muscle in modern herbivorous and carnivorous birds. This is a major muscle that powers bird bites, and the herbivorous, seed-cracking birds typically had wider muscles with increased space for attachment on the lower jaw. That fits they way they feed. Much more power is needed to bust open hard fruits than to tear soft flesh.

The actual muscles of Gastornis rotted away over 40 million years ago, but the bird’s lower jaw shows a wide space for the external adductor muscle to attach. Taken together, the bird’s beak, feet, reconstructed musculature, and chemical signature best fit a large herbivore that snacked on plants rather than the mammals that lived underfoot.

(Read more at Phenomena: Laelaps)

#paleontology #extinct birds #terror bird #Gastornis #Gastornithidae #Anseriformes #Galloanserae #Aves #birds #Paleocene #Eocene #ornithology #zoology #biochemistry

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  13. bringmeknitting reblogged this from pfowolf and added:
    Dammit. Gastornis was badass as a carnivore. Hey-ho.
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    http://en.wikipedia.org/wiki/Gastornis
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    Now that’s pretty interesting. Cheer up, little Eohippus! No more fear of dawn horse-crushing big birds!
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