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Bill Stanley tells us all about the weird and wonderful Hero Shrew, and reveals his latest discovery!

Read more about Thor's Hero Shrew (Scutisorex thori) :


The Brain Scoop is written and hosted by:
Emily Graslie

Created By:
Hank Green

Directed, Edited, Animated, and Scored by:
Michael Aranda

Huge thanks to Bill Stanley for helping to make this episode possible!

Filmed on Location and Supported by:
The Field Museum in Chicago, IL

Closed captions by Luca Vittone, TBSkyen, Alexander Austin, Tony Chu, Mariano Cepeda, Míchaela Medková, Anne-Sophie Caron, Seth Bergenholtz. and Marie-Elsa Beaudon. Thanks a million!

Bill Stanley: There were two explorers that were in eastern Congo that noticed a shrew that was the size of a small rat and was very furry. In all other ways, it looked like a shrew. It had a pointed nose and black coloring.

Emily: That seems kinda big for a shrew. Rat size?... Okay.

B: It is- it was a big. And small rat size, which is huge for a shrew,

E: Yeah.

B: This was a big shrew, and so these guys said, "That's a pretty interesting shrew," and the local residents said, "watch this," and they took a living shrew, and they put it on the ground and a full grown man stood on it for five minutes, and then stepped off, and this animal walked away. And, if it had been any other- a rodent that size or another shrew that size, it would have been squashed flat. So these folks collected a series of specimens and decided, "Let's dissect one and see what the vertebral column looks like."

E: It looks like a Triscuit.

B: Let me show you what the next largest shrew would look like. Just like you and I, there are five lumbar vertebrae, and there are processes, just one or two, that stick out on either side, and then a dorsal process. This is a hero shrew, and there are ten to eleven lumbar vertebrae and each vertebrae has ten to twenty processes sticking out the side, and they are interlocked. So, you and I have, uh, lumbar vertebrae that a quite a bit bigger than the lumbar vertebrae of this shrew, but for the most part, look the same. A camel, a bat. All of these animals have lumbar vertebrae that look relatively the same. The Scutisorex is the most bizarre mammalian backbone within the entire group of mammals because of this morphology, and it actually stretches even into the thoracic region there, you can see it. That's expanded as well.

E: Yeah. Why? Why?

B: We didn't know, and in fact, we may still not know, but that's part of this story. For over 100 years since its discovery, the hero shrew has been known by only one species. And all the other shrews have a backbone that looks like this.

E: Yeah.

B: Many people think of evolution, uh. You could take this form here, and the form at the beginning and the two would look completely different from one another, but you have these transformational forms in between that show the gradual change.

E: The missing links.

B: Exactly.

E: Okay.

B: There were no links in this- from this to that. Some people suggested well, perhaps this change went directly from this form to that form. Two years ago in the Congo, we found another species of hero shrew, which is here. And you can see, that first of all, there are less lumbar vertebrae. There are eight in this form. There are ten to eleven here.

E: Mhmm.

B: And you can also see that the processes on this one are less, and they're bigger than here.

E: Ohhhh.

B: So, uh, we have a form that may, and I say 'may' because this may not be the case, but this very well could represent an intermediate form between this guy and that guy.

E: The missing link.

B: The missing link. Now, th- the aspect of this story that I think is the most intriguing is what benefit does this backbone provide this animal?

E: Mhmm.

B: I remembered a conversation I had at the American Society of Mammalogists meetings in Missouri, about 15 years ago with Lynn Robbins. He said, "When I was in the Congo, I was asking local residents about where I could find hero shrews and they said, 'Oh, come with us when we go to the palm trees to harvest beetle grubs, 'cause we always see them running around the base of the palm trees." And Lynn thought to himself, these people are pulling the bracts of the palm trees away from the trunk to access these huge beetle grubs. Maybe Scutisorex is inserting itself in between the trunk and the leaf base and bending its back and able to pry the leaf base away and then access these concentrated sources of food that would be inaccessible to any other predator.

E: So it has a built-in crowbar.

B: So when I realized we had a new species of hero shrew, I called him up. I hadn't talked to him since the meetings.

E: Yeah.

B: I said, "Lynn! You gotta join us on this," and this is the perfect place to publish this hypothesis.

E: Mhmm.

B: Because we'd- neither of us have seen Scutisorex do this, so that's all this is, is it's a hypothesis.

E: Mhmm.

B: But that's how science works.

E: Yeah.

B: You get the idea out there and other scientists uh, subsequently, will make observations and see if, in fact, that happens or not.

E: How many of these do we have here?

B: We probably have twenty.

E: Twenty? Oh, that seems like a lot. I was-

B: Yeah.

E: How many of- How many of these exist? One. This one.

B: This one.

E: This is-

B: This is the holotype.

E: This is the only one in any museum. In the world.

B: In the world.

E: And you're holding it right there.

B: Right there. In my left hand.

E: This is so exciting!

B: Oh yeah, its-

E: I feel kind of honored to, like, be talking to you right now, knowing that-

B: You can hold it.

E: I ca- Oh my gosh. This is- This is it. This is the only one. This is so exciting. This is science.


E: It still has brains on it.