Did Dreadnoughtus Really Have Air Sacs?
Beloved sauropod Dreadnoughtus is featured in the Apple TV+ show PREHISTORIC PLANET, episode 2 "Deserts." Paleontologist Dr. Kenneth Lacovara discusses their presentation and how accurate the dinosaurs were depicted.
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00:00 was quite a long scene of Dreadnoughtus. Here they are.
00:04 >> A fight scene. >> It was a fight scene in this territorial
00:10 battle between males. And I think this was actually kind of based on our science, because
00:17 what we found with the two Dreadnoughtus individuals is that the much larger one, the 65-ton one,
00:24 was osteologically, that means its bones, was osteologically quite young. You might
00:29 even think of it as a teenager who was growing rapidly at the time of its death. Whereas
00:34 the one that we found that was one-third smaller osteologically was much, much older. And so
00:41 where do you find this in animals today, where you find older, smaller individuals and younger,
00:46 bigger individuals? That's in species where you have sexual dimorphism, where the two
00:52 sexes are of different sizes. And usually that happens where you have male-dominated
00:58 sexual selection, which means that two alpha males are going to compete with each other
01:02 to control a territory or a group of females. There's also female-dominated sexual selection.
01:09 That's where you see the males showing off with all kinds of colors and doing fancy tricks
01:13 and buying Corvettes and things like that. And so with Dreadnoughtus, we have just a
01:19 hint that we have sexual dimorphism, and then kind of a hint, based on a hint, that maybe
01:27 it was male-dominated sexual selection. And that's what you are seeing here.
01:32 And then-
01:33 These air sacs, we got to talk about these air sacs.
01:35 Yeah, let's talk about the air sacs. What do you think about that?
01:37 Well, the air sacs are kind of hard to miss. I have to tell you that there is zero evidence
01:43 that Dreadnoughtus had air sacs. These are pneumatic goulard pouches like a grouse would
01:49 have today. Is it impossible? No, it's not impossible, but we don't have any evidence
01:56 that they do have that. Now, I was told by the consultant on the show that they wanted
02:03 to find a way to illustrate the fact that extinct animals must have had amazing soft
02:10 tissue structures that will never be preserved in the fossil record, which is certainly true.
02:15 If we only knew elephants from their skeletons, I probably wouldn't really know what an elephant
02:20 looked like. So this is an example of a hypothetical feature that maybe we're missing completely
02:28 in the fossil record that could have existed. Did they specifically have this? Probably
02:34 not. Is it impossible that they had this? No, it's also not, but we don't have any evidence
02:39 of it. What we do have though, is we have their cervical vertebrae, cervical vertebrae.
02:45 And the cervical vertebrae are very pneumatic, meaning that they have a system of air tubes
02:51 and air bladders that invade the bone over the lifetime of the animal. So the bone becomes
02:57 more honeycombed with air over time, making it very light, but still retaining most of
03:02 the strength. Because if you have a 40 foot long neck, right, a 40 foot long lever, you
03:07 don't want to put a lot of weight at the end of that lever. So they have these very lightly
03:12 built pneumatic necks, which I guess gave them the idea, okay, there's air in the neck.
03:17 There's a lot of air in the neck. Why not something like male grouses in the breeding
03:22 season that have these pneumatic cooler pouches that pop out like that?
03:27 Thinking of a story of Dreadnoughtus. I know it's always interesting to draw inspiration
03:34 from modern creatures. There he goes. I guess we'll have to hold out for any more fossil
03:41 or soft tissue preservation. Yeah. There's certain things that we're just
03:45 never going to know and we kind of have to live with that disappointment. But there are
03:50 a lot of soft tissue features that extinct creatures have that we're just never going
03:54 to find. We can make inferences about them. Sometimes we can do that from molecular work
04:00 with modern creatures. We can look at the DNA from groups of related creatures and kind
04:06 of figure out where that trait must have started. Occasionally you get soft tissue structures
04:14 preserved if you have very clay deposits that can preserve that kind of resolution, but
04:21 that's very rare. And I don't see that scenario happening for big things like sauropods. That
04:24 happens for little things like birds. And then there's always the promise of molecular
04:30 paleontology where we routinely recover blood vessels and blood cells and proteins from
04:38 dinosaurs and other extinct creatures. A few DNA bases have been recovered. Is it possible
04:44 we'll have a genome of a dinosaur, a non-avian dinosaur in the future? I don't know. It's
04:50 a pretty high mountain to climb, but I can't say that it's impossible.