(Intro)

So we're here in oversized geology surrounded by dinosaurs and pretty much any other prehistoric life that is too big to go anywhere else in the museum, and we're here with Joyce Havstad, who quite possibly has a job title almost as great as mine, what is your role here at The Field Museum?

Joyce: People around here call me the Philosopher in Residence.  

All knowledge must come through the senses.  

Emily: At The Field Museum, what are some of the concepts or ideas that you've pursued in your post-doc residency here?

Joyce: Holotypes.  Holotypes are the individual physical specimens that bears the name for and acts as the exemplar of a species as a whole.

Emily: It's the basis, it's the gold standard for--

Joyce:  Yeah, it's the universal standard.  It's the yardstick that you sort of measure up other organisms that you think might belong to that species, you see whether they match or not.

Emily: So it seems to make a lot of sense and it would be really easy with a massive library of millions of comparable specimens if you find something existing today, but what do you do in the case of the fossil record where you might not have a complete skeleton of something, how do you know if it's a new species or not?

Joyce: Do you know about the meter bar?  Back when science was just getting off the ground, the guys doing science realized we needed a universal standard of measurement.  We needed like, a distance that we could all agree on, and that was the meter, and they argued about how long a meter should be, and eventually they decided it was gonna be like, one ten-millionth of the distance between the equator and the North Pole, but so then they had to figure out how long that distance was, right, what's one ten-millionth of the distance between the equator and the North Pole?  So they sent some guys out who spent almost ten years measuring the distance between this belfry in Dunkirk and a castle in Catalonia, but eventually, everyone realized that we needed, like, an official bar--

Emily: Yeah.

Joyce: --that was like, the prototype meter.  In 1889, they made a bar of like, 90% platinum and 10% iridium and they put two lines on it, and they keep it at the temperature of melting ice, and the distance between those two lines on the bars at that temperature is a meter.  

Okay, but so you asked about paleontology, right.  Now, imagine if when a scientist, you know, wanted to know how long is a meter and someone was like, "Okay, well, it's right there."  They only had the bits and pieces of the meter stick, it had been like, chunked up and it was missing and had been thrown all over the room, right?  That's the kind of situation that paleontologists are dealing with when they're trying to, you know, point to and figure out what's the specimen that represents an entire species like Brachiosaurus.  

We're standing in the holotype of Brachiosaurus.  It was declared the largest dinosaur known when it was discovered on the 4th of July in 1900 by Elmer Riggs, Field Museum scientist.  So Brachiosaurus, what do we have of it?  We have seven vertebrae, the sacrum, two caudals, four dorsal ribs, a coracoid, humerus, ilium, and a femur.

Emily: And this is the femur.

Joyce: This is the femur.  

Emily: So what is that, like, about 14 bones of the Brachiosaurus?  
Joyce: It's about 20%

Emily: About 20%

Joyce: --of the whole skeleton.  It's still the most complete Brachiosaurus specimen that we have.  

Emily Can you imagine what Elmer Riggs was thinking when he uncovered this sort of thing?  Is his first thought being like, "I've discovered a new species", like, what do you think went through his head and then afterwards, how did he determine that this was the holotype of a brand new species?

Joyce: One of the things about the Brachiosaurus that's really interesting and that was definitive for Riggs in, you know, thinking that this was a unique sauropod, a huge gigantic unique sauropod, is a bit of information that we get from the fact, actually, that we have the femur and the humerus.  So look at this femur right, it's huge and it's long.

Emily: Yeah.  Right.

Joyce: But guess what?  The humerus is even longer than the femur.  

Emily: Really?

Joyce: The humerus is longer.  

Emily: So it kind of had a like, it was a little short in the back?

Joyce: Yes.  Now, think about what other animals that looks like.

Emily: That's a great question.

Joyce: With the shorter legs and the longer arms?  That would tilt you up, right?  

Emily: Yeah.

Joyce: So like, normal sauropods with the--

Emily: Like a giraffe.  Like a giraffe!

Joyce: Like a giraffe.  The other species, the most closely related species to Brachiosaurus are actually they're named after a giraffe.  It showed that this wasn't the leg evenly balanced, it was the tilted up, long-neck, I mean, that tells us about ecology as well, right?  So, likely to be feeding on foliage from trees and not necessarily grazing on grass, right?  There's just so much we can learn from the ratio between the femur and the humerus.

Emily: Oh, that's exciting.  Oh, okay, no, that's really--I'm impressed with how I drew that conclusion.  Ah, I was right.  Not that I accomplished anything, I just--I think that's a really exciting way to look at just a little bit of information and being able to infer as much as possible by critically looking at the small bits and pieces that you have.

Joyce: That's what's going on.  It's the sort of detective work that paleontologists are doing with even just the partial skeletons and in working with these holotypes, and that's the kind of characteristic feature that would, you know, make someone have a good solid argument like Riggs, give him a good argument for thinking, "Look, this is its own--this is its own unique species.  This is a holotype."

Emily: Awesome.

Joyce: "I've discovered a new species, and it's the largest dinosaur ever."

Emily: I bet he felt pretty good at the end of that day.

Joyce: Yeah, he was pretty psyched, I think.

(Credits)

Emily: It still has brains on it.