It is becoming increasingly clear that birds are nothing more than feathered dinosaurs. Not only the plumage, with which so many monsters of the Mesozoic adorned themselves, points to this. The dinosaurs may have already developed the highly effective lungs of today's birds.
Whether imperial eagle, nightingale or simply a vulgar pigeon - almost 10,000 different bird species delight the heart of every ornithologist. What many bird lovers might not be aware of is that their feathered friends are descendants of creatures that once ruled the earth: dinosaurs.
The close relationship between birds and dinosaurs became clear as early as 1861 with the discovery of the primeval bird Archeopteryx. In the meantime, more and more remains of the "Terrible Lizards" have turned up, proving that the feather is not an invention of modern birds. T. rex and co could probably not fly with it yet, but feathers may have been helpful as a warming insulating layer as early as the Mesozoic. And some fossil finds even indicate that the animals, notorious as brutal killing machines, also turned out to be caring parents who protected their young like mother hens.
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But one achievement that even modern mammals envy has not been denied to birds: their respiratory system. Because in contrast to mammals with their rather inefficiently working lungs - not to mention reptiles - birds have a sophisticated technology at their disposal: In addition to the actual respiratory organ, they have a complex system of parallel and consecutive air sacs, which sit as bellows throughout the body and even penetrate the bones to the tips of the wings.
When a bird breathes in, the air first gets into the rear air sacs, while the front air sacs suck used air out of the lungs. When you exhale, the rear air sacs press the gas into the lungs, while the front ones empty. As a result, the lungs are perfused in one direction, but twice - both when inhaling and when exhaling. With each breath, the system completely exchanges the air in the lungs and can thus make maximum use of the oxygen content.
The pulmonary system of carnivorous dinosaurs is similar in many ways to that of modern birds
(Leon Claessens) The bird lung with its air sacs is one of the most effective respiratory systems that nature has to offer. Since it penetrates the entire bird's body, it also serves as an air conditioner, with which the heat from the flight muscles can be dissipated. And the air-filled bones ensure a lightweight construction that is optimal in terms of flight technology.
It seemed hard to imagine that dinosaurs also had this modern design. They were only granted a similarly primitive structure, as is also the case in today's crocodiles. Patrick O'Connor wasn't so sure about that, though. The Ohio University biologist toured with Leon Claessens, browsing the zoological and paleontological collections in New York, Berkeley, Chicago, Pittsburgh, Washington, London and Berlin.
Here they could compare modern bird architecture with ancient dinosaur bones. The researchers also had the remains of Majungatholus atopus, a 67-million-year-old predatory dinosaur up to 30 feet tall that O'Connor unearthed in Madagascar in 1996.
And here parallels between modern birds and the extinct giant lizards actually showed up. In the spine in particular, but also in the ribs of the predatory dinosaurs, the researchers were able to identify structures reminiscent of the air-filled cavities of birds.
"The pulmonary system of carnivorous dinosaurs like T. rex is indeed structurally similar in many respects to that of modern birds, which technically have the most efficient respiratory system of any terrestrial or aquatic vertebrate," Claessens points out.
One question remains unanswered: Were the dinosaurs warm-blooded like today's birds? O'Connor and Claessens don't want to commit themselves here, but a number of their colleagues are convinced of it. The monsters of the Mesozoic would have fulfilled the technical requirements. In view of its formidable ancestors, at least even the smallest sparrow deserves a little respect.