Briefing chat: Spinosaurs with salt glands could have lived in marine environments

**Benjamin Thompson** (0:04)
Hi, listeners, Benjamin here, welcome to the briefing show, the Friday podcast, where we talk about a few stories we've read about in the Nature Briefing, which is, of course, Nature's daily email roundup of the latest science news. We've got a couple of stories to talk about today. And joining me to do so is the one and only Marin Hantzberger. Marin, how are you doing?

**Maren Hunsberger** (0:23)
Hello, hello, I'm doing great. I'm really excited to talk to you today about dinosaurs.

**Benjamin Thompson** (0:27)
Have at it then, let's go, dinosaurs. What's going on with them?

**Maren Hunsberger** (0:30)
This story is about a particularly charismatic looking dinosaur. It's called the Spinosaurus, Ben. And it's called a Spinosaurus because it has these elongated vertebrae on its back, which support this big membrane. So it has this thing protruding off its back that makes it look like a big sail. And Spinosauruses typically tended to live in more coastal areas. And there's been a lot of debate amongst paleontologists throughout the years, just how much of their lives exactly they spent aquatically versus on land. And now, there's paper out in Historical Biology. I read an article about this in Science. And that has some new evidence shedding a little bit more light on where these Spinosauruses may have actually lived.

**Benjamin Thompson** (1:08)
Oh, right. Because I guess it's really hard to work out what an animal's behavior was like from its bones. So how have they gone about working out whereabouts it may have paddled, I suppose?

**Maren Hunsberger** (1:21)
Exactly. Well, it's very tricky to piece things together like that from the fossil record. But there are certain parts of its anatomy that indicate that it might have had these big paddle-like fins to swim around with. But this new evidence is about something called the supra-orbitally placed salt gland, Ben, or more catchily known as the SSG.

**Benjamin Thompson** (1:41)
Oh, the SSG. Right. You've said orbital there. I'm guessing this isn't to do with space. What is this?

**Maren Hunsberger** (1:46)
Correct. Eyeballs, Ben. So there's lots of evolutionary considerations that come with living in a salty environment. If something's coastal, that means that you're by the sea, therefore that comes with salt. And obviously our bodies have to maintain a really careful balance of salt in order to remain functional. All of our cells rely on osmotic balance, fluid flowing from one area to another to maintain the ideal ratio of salt. So animals that live in coastal environments and that eat a lot of fish, maybe have to work really hard to maintain their body's osmotic balance. Animals today that have to contend with this are things like crocodiles that often live in marshy, brackish areas. They have a specialized gland that allows them to excrete excess salt. Marine iguanas also have these. Fun fact, alligators don't have this gland, which is why they actually have to return periodically to freshwater so they can maintain their osmotic balance. And marine birds also have this specialized gland. So in this new paper, the researchers found evidence that at least some spinosauruses also had these supraorbitally placed salt glands, which indicates that they had to have a way to excrete excess salt, which means they were living in a salty area, which means we might now have more evidence for the aquatic side of the argument than we had before.

**Benjamin Thompson** (3:05)
Right. I mean, I guess certainly when it comes to thinking about birds, there is a through line between our avian friends and the dinosaurs.

**Maren Hunsberger** (3:15)
Yes, exactly. And actually one of my favorite lines from this paper is the first one from the abstract, which is, despite their exceptional diversification on land, non-avian dinosaurs barely exploited the marine realm, which seems like a little bit of a dunk on the dinosaurs. But this paper posits that potentially that was because of this specialized cranial anatomy that is required to excrete excess salt. Birds could do it, so they were able to diversify into more marine environments, but fewer dinosaurs were able to exploit this more amphibious area between land and the ocean.

**Benjamin Thompson** (3:49)
Except the spinosaurus, then, which evidence suggests was getting it done. Obviously anything to do with fossils is difficult because you're making inferences. What did the researchers do in this instance to lead them to think that there was this gland?

**Maren Hunsberger** (4:01)
Yeah, it's absolutely incredible. As a non-paleontologist, I'm looking at the pictures in the paper, and I'm like, I don't know what you guys are seeing, but obviously, they are so familiar with dinosaur anatomy and how that's evidenced in the bones that they find that they can tell which divots are actually anatomically included in the fossil versus just weathering or due to the way it was dug out of the ground. And I think a great quote that reflects this is a paleontologist at Queen Mary University, David Hone, who wasn't involved in the research, puts it perfectly when he says it's impressive that these researchers were able to draw out this data from very limited fossil remains. So even the most subtle, tiny indentations and divots in dinosaur fossils can tell us so much about how they may have lived their lives.