First Geology Fact of the Day
- kmmbober
- Apr 14, 2021
- 2 min read
Welcome to Day 1 of Geology Fact of the Day!
For our first topic, let's discuss paleontology. In particular, dinosaurs.
The specific topic will be, "How did they breathe?"
"Well, didn't they breathe like other terrestrial animals?" I hear you cry.
Yes, but which ones?
One of the most well-known dinosaur clades, thanks to media like "Jurassic Park," is the subgroup known as the sauropods.
You know, the long-necked things with long tails. The ones you always see in any dinosaur play-set.
It's still a mystery to paleontologists how they lived.
Paleontologists are still wondering how they managed to get as many nutrients as their bodies would have required, given their neck length.
"So sauropods breathed like every other terrestrial animal, though, right?"
No, because not all terrestrial animals breathe the same way.
"Okay, so which ones breathe differently, and how do they?"
Birds have a different mechanism in place for breathing. They rely on air pockets within their bones to act as bellows to pump air through their lungs.
They lack diaphragms, so they rely on air pockets.
Reptiles, on the other hand, breathe much the same way we do, using their lungs to suck in air and push that oxygen through their bodies.
Their scales actually prevent them from breathing through their skin, as amphibians can.
The trade-off is that they have a greater surface area in their lungs than do amphibians.
"... What does this have to do with dinosaurs?"
Everything. Particularly in the case of the sauropods' breathing mechanism.
You might believe that, because sauropods and other dinosaurs so closely resemble modern reptiles, that they would breathe the same way.
This is not correct.
You might also think that sauropods, because of their size, were extremely heavy.
Not as heavy as you think.
Sauropods had holes in their bones. I mean, more holes than you would expect in a skeleton of a human or crocodile. These are no ordinary holes. They are, in fact, spaces for air sacs. This is why sauropods were lighter in density than one would expect.
But what else?
Not all sauropods had the same quantity and location of air sacs, but they were still there, helping sauropods to push oxygen through their lungs.
In this way, they breathed like birds. The quality of having bones with air pockets is known as pneumatization.
“But how do we know there were air sacs in there?”
Good point: air sacs were of a more fleshy consistency than the bones encasing them, and were easily decomposed. We can’t see them in dinosaur fossils today.
But certain paleontologists knew how air sacs developed in birds.
Birds typically develop their air sacs in the front first, followed by air sacs in the back. These air sacs invade the bones, spreading up and down the vertebral column until they meet in the middle.
Sometimes, due to a developmental error, they never meet in the middle.
This leaves the bird with certain vertebrae which are never "hollowed" or filled out with air sacs.
There was evidence in papers from the early 1900s, in which sauropods' middle vertebrae were described as solid, but the fore and rear vertebrae were pneumatized.
Thank you for joining us for the first geology fact of the day!
I hope you learned something, and will continue to learn through your own native curiosity.
Sources:
Museum of the Rockies, July 2020 visit.
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