Argentine paleontologists recently discovered the first clear evidence that a group of theropod dinosaurs have hollow bones that can hold air sacs. study Published in PLOS 1.
This finding adds to an increasing number of studies that revealed that all theropods and sauropods may have bones with air sacs.
“This is one of the features they inherited. [from a common ancestor]says Guillermo Windholtz, a paleontologist at Argentina’s National Council on Science and Technology Research (Conicet) and National University of Rio Negro. “This is why actual birds fly – it’s a really crazy feature.”
Hollow bone dinosaur
Alvarezauride was a group of theropod dinosaurs that lived primarily in late Cretaceous Argentina about 86 million years ago, 83 million years ago. They were not big – the smallest of them was almost chicken size, while the largest found were about 10 to 13 feet long from nose to tail.
It is unknown what these creatures ate, but based on their teeth, they were carnivorous, says Windholtz.
Birds today have hollow bones, providing space for the air sacs of soft tissues connected to the lungs. These functions help brighten the bird’s body. It’s especially important for flight.
Pterosaurs and some dinosaurs also have hollow bones, but it is not entirely clear that these functions allowed for air sac space. A study published in 2022 Some of the oldest known Abemetatalusals, birds, pterosaurus and dinosaurs discovered that there were no traces of air sacs. Nor were Oriccisians, one of three major groups of dinosaurs along with theropods and sauropods. However, all Sauricians investigated so far had these functions.
read more: As meat-eating hunters with strong jaws, theropods ruled the Mesozoic Era
Examining hollow bones with a CT scan
Most dinosaur bones are simply being examined on the outside. You need to open them to determine whether they are hollow or not. So, although some are considered hollow, many dinosaur bones have not been thoroughly examined sufficiently to prove that the cavity within the vertebrae is somehow connected to the lungs. This means it is difficult to determine whether these cavities contain air sacs similar to birds today.
However, techniques like CT scans allowed us to investigate the interior of the fossil more thoroughly.
In a recent study, Windholtz and his colleagues did exactly that, scanning 11 vertebrae from various things Bonapartenykus Ultimate Specimen.
The CT scan revealed: B. Ultimate The spine was actually hollow – it was not a surprise as most other theropods and sauropods had hollow bones. However, not all vertebrae are pneumatic. Some theropods have a caudal vertebrae that is not filled with air, says Windholtz.
However, the scan allowed Windholz and his colleagues to confirm that these hollow cavities within the vertebrate were connected outwardly through cortical openings called Foramina. Essentially, these are passageways that may have moved from the lungs of a dinosaur to the medial spine and the medial back.
Why do dinosaurs have hollow bones?
Windholz’s recent work has helped to improve paleontologists’ knowledge of the use of these hollow cavity in theropods. At least in Alvarezsaurs, the cavity has been confirmed to have been used in the air sac.
It is more difficult to determine why these creatures needed hollow bones and air sacs in their vertebrae. For fast-moving theropods, hollow bones may have helped to increase speed by reducing loading.
But if this is true, why do large sauropods have hollow bones? Perhaps these big creatures, roaming around with four hard legs, weren’t about to fly, after all. Some scientists speculate that it may have helped brighten their finest masses when the hollow bones were moving around, but there is not necessarily a consensus on this, Windholtz says.
A 2022 study suggested that sauropods, pterosaurs, and theropods may evolve their air sacs in their bones independently of each other. However, this may be because vertebrae from a more recent common ancestor of Abemetatalusals who have evidence of air sacs have not yet been examined or found.
If there is a common ancestor, it is also possible that the hollow bones are relics from these dinosaurs, Windholtz says. For example, what was useful in the Saurysians may have been inherently useless in sauropods and theropods.
At least the birds and their direct ancestors came and flew with these air-filled bones.
read more: About 120 million years ago, a giant clawed theropod may have ruled Australia
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Joshua Rapp Learn is an award-winning DC-based science writer. As an expatriate Albertan, he has contributed to many scientific publications such as National Geographic, The New York Times, The Guardian, New Scientist, Hakai and more.
