Happy 70th, Coelophysis!

by AMNH on Jun 22, 2017 2:54 pm

Seventy years ago today, Museum paleontologists led by Edwin Colbert working at New Mexico’s Ghost Ranch site turned up an amazing find—a bone bed containing numerous stunningly preserved specimens of Coelophysis bauri.

A Western Union telegram dated June 30, 1947 to Carl Sorensen from Simpson Colberg beginning "Struck rich at quarry need extra help."

An excited telegram from the Museum's team in the field at Ghost Ranch to the Paleontology Department on June 30, 1947.
©AMNH

At about 8-feet-long and running on two feet, one of these predators would have looked like a miniature T. rex.

Colorful artistic rendering of a Coelophysis bauri dinosaur with fuzzy skin, short claw-like arms and colorful spots.

Artist's rendering of a living Coelophysis bauri.
Courtesy of National Park Service/J. Martz

If you’re visiting the Museum, you can come to the Hall of Saurischian Dinosaurs to see the “death assemblage” of Coelophsyis fossils. You can also get a feel for the specimen in the 81st Street subway station that serves the Museum—the Coelophysis assemblage is one of the fossils replicated in bronze along the station’s walls.

Bronze cast of a Coelophysis bauri fossil on display on the wall of the 81st Street subway station.

The bronze cast of Coelophysis bauri in the 81st Street subway station.
© AMNH/M. Shanley

And if you can’t visit, don’t worry. You can still learn all about Coelophysis and the many other fossils that have been discovered at Ghost Ranch courtesy of the Museum’s web series, Shelf Life.

STERLING NESBITT (Research Associate, Division of Paleontology): Ghost Ranch is kind of the idealistic Old Western set. There are these beautiful red cliffs that are surrounding the ranch itself. But down in the basin, just below Ghost Ranch, you get red, and purple, and green, and white Badlands. And those are the places that are really good to find fossils. It’s definitely the best place to find early carnivorous dinosaurs in the world.

I’m Sterling Nesbitt. I am a research associate of the American Museum.

[SHELF LIFE TITLE SEQUENCE]

NESBITT: So, starting in 1881, there’ve been a number of paleontologists that have searched these beds.

MARK NORRELL (Macauley Curator, Division of Paleontology): It really wasn’t until the 1940s, right after World War II that one of my predecessors, Ned Colbert, began excavating at Ghost Ranch. When Ned Colbert, his assistant George Whitaker first discovered the quarry they thought it was probably just one or two little dinosaurs sticking out of the side of the cliff. But it is one of the world’s great deposits of dinosaurs of any kind.

My name’s Mark Norell and I’m the Macauley Curator of Paleontology at the American Museum of Natural History.

It’s really unusual to find mass assemblages of dinosaurs. Occasionally we find things called bone beds, where we find lots of different species and we find single individual bones, but the thing that makes Ghost Ranch so special is so many of the entire skeletons are there – just piled on top of one another.

NESBITT: Most of what Colbert saw were these delicate bones of a carnivorous dinosaur named Coelophysis bauri.

When dinosaurs first appear, they weren’t the big animals on the block yet. They didn’t dominate ecosystems anywhere in the world. They were all pretty small. And when people think of dinosaurs, they usually think of T. rex or giant sauropods like Apatosaurus, but this is what probably all early dinosaurs looked like. And then later they grew into the gigantic monsters in movies and in dinosaur halls.

DANNY BARTA (PhD Student, Richard Gilder Graduate School): Ghost Ranch preserves our most detailed picture of late Triassic, that is about 200 million years ago, ecosystems in North America. Having all the Coelophysis specimens together in one bone bed like this, it’s the closest we as paleontologists can ever come to really, truly finding an equivalent of a living population.

I’m Danny Barta. I’m a PhD student in the Richard Gilder Graduate School at the American Museum of Natural History.

I’m interested in the growth and development of dinosaurs, particularly Coelophysis because Coelophysis sort of set the standard for this body plan that we saw later carried to extremes in Tyrannosaurus and then Velociraptor. And this is the group that gave rise to birds.

NESBITT: We have an okay handle on the anatomy, but we don’t know lots of details. So, even though thousands of skeletons may have been preserved, only a few dozen really are prepared and out of those, only a few are really prepared well.

These bones are really delicate, and once you expose some of these bones in the field, or you have uncontrolled conditions, they just break. And you can’t get the pieces back together.

So, instead of taking each bone out individually, Colbert took out these big blocks of rock and bone and everything else, wrapped them in plaster, and brought them here.

NORRELL: One of the things I think people don’t understand about collecting fossils is we go out on an expedition, it’s hard work, but what really takes the time is the preparation that we have to do to be able to expose these things.

So, when you look around a room like this, you look around the rooms that we have with the unopened blocks – these are really just libraries of objects. And it’s like if someone goes to the Vatican archives and they find, you know, something that was either penned by Leonardo or a Mozart manuscript.

That’s what we have here, and while it might take a while for it to be discovered at least it’s safe here and it’s amenable to using new technology on, and it allows a whole future generation of scientists to be able to look at these things almost in their original contexts.

BARTA: So, with the specimens here, I will be making very thin sections of the long bones of Coelophysis, usually about 50 or 30 microns. We have to be able to pass light through them. When we look at them under a microscope, we often see growth rings, analogous to tree rings. And so, we can count, you know, essentially one growth ring for every year. And this gives us an idea of how old all of the individuals in a population were when they died.

Coelophysis is really in some ways kind of a model dinosaur for understanding dinosaur growth. By studying, you know, what Coelophysis growth rate and metabolism may have been like, this will give us more detailed insight into how some of the evolutionary innovations we typically think of as occurring in birds—you know, high metabolism, warm-bloodedness—when exactly all of those things evolved.

These historic collections that were collected almost 70 years ago have so much to teach us. By applying, you know, techniques that have really only been developed in the last 30 years or so, like CT scanning and bone histology, we’re able to gather a lot more data than we would have ever thought possible back when Coelophysis was first discovered.

NORRELL: One of the real interesting things about Ghost Ranch is that it’s come back into a real place of prominence in paleontology right now.

NESBITT: This is our tenth field season out there. And we’re working in the formation just below where the Coelophysis quarry was found. So, it’s a bit older. We don’t know how much older— maybe five to seven million years older— but what we have are relatives of dinosaurs. And we have some earlier carnivorous dinosaurs that are unlike anything else found anywhere else in the world.

NORRELL: It’s not just the place where dinosaurs were found 75 years ago. It’s the place where dinosaurs are found today.