What Lies Beneath

Cradled in a bed of felt and fiberglass in the basement of Carnegie Museum of Natural History is the fossilized jawbone of the first thing in history to ever be called Tyrannosaurus rex.

The 66-million-year-old carnivore’s jawbone still bears the serrated, banana-sized teeth that were used to rip through the flesh of its prey.

When this fossil was discovered in Montana in 1902, it was a revelation. What is today one of the most recognizable dinosaurs was then completely unknown. The find was but one piece of the puzzle that would become the T. rex holotype, or the name-bearing specimen upon which the entire species is based.

The museum purchased the fossilized T. rex skeleton from the American Museum of Natural History in 1941, and it continues to thrill visitors in Pittsburgh as part of the Dinosaurs in Their Time exhibition. But the head on display is a reproduction. The real fossil skull bones are too heavy, fragile, and scientifically significant to be on public view.

Instead, they reside in one of two underground rooms referred to by museum staff as the “Big Bone Room” and the “Little Bone Room,” where the bulk of the museum’s vertebrate paleontology collection is kept and cared for.

The collection’s size, breadth, and scientific significance distinguish it as one of the finest in the world, containing specimens—including the T. rex holotype—that continue to shape humanity’s understanding of the history of life on Earth.

“These rooms hold one of the world’s great vertebrate paleontology collections,” says Matt Lamanna, the museum’s Mary R. Dawson Curator  of Vertebrate Paleontology.

Into the Bone Zone

Vertebrate paleontology is the study of prehistoric animals with backbones, and their fossils are carefully stored in nearly every square inch of the “bone rooms.”

The Big Bone Room (which, like its smaller counterpart, is named for the size of the space, not the size of its specimens) is larger than a basketball court, with low, whitewashed ceilings and dozens of shelves holding fossils, some still wrapped in protective materials.

Photo: John Schisler

The Little Bone Room is a short jaunt down a hallway, where the polished concrete floors are still veined with tracks that were once used to move heavy specimens via rail cart into the museum’s basement over a century ago.

Like the Big Bone Room, the space boasts rows of movable shelves and drawers that date back to the early 20th century. All told, the collection contains about 120,000 specimens, approximately 500 of which are holotypes. They range in age from 450 million years old to 500 years old and come from every continent, including Antarctica.

Since Andrew Carnegie started it in the 1890s, the collection has produced groundbreaking discoveries. This includes the first 50-million-year-old mammals ever found in the Arctic—a find made in the 1970s by paleontology pioneer and former head of the museum’s vertebrate paleontology program Mary Dawson. It also boasts the holotype skeleton of Anzu wyliei, a 7-foot-tall feathered dinosaur that received its name from Lamanna and three colleagues in 2014.

The contents of the bone rooms draw researchers from around the world. The museum’s fossils of the gigantic, long-necked herbivorous dinosaurs known as sauropods are among the most scientifically important on the planet.

“More information about sauropods has been derived from our collection than maybe any other,” says Lamanna.

“The Carnegie paleontology collections—you just can’t beat them,” adds paleontologist and evolutionary biologist Sarah Davis. “Especially for large dinosaurs.”

The bone rooms are Davis’ domain. She’s the museum’s collection manager of paleobiology, a position she took in April 2024 following the retirement of longtime collection manager Amy Henrici.

Davis cares for a staggeringly diverse assemblage of fossils, most of which are not on display.

Some are smaller than the head of a pin. That includes the holotype specimen—a tooth—of the 56-million-year-old Teilhardina magnoliana, one of the geologically oldest primates ever discovered in North America. In life, the tree-dwelling, marmoset-like creature weighed less than an ounce. Dental fossils are often the only surviving evidence that these tiny animals existed.

Other specimens are comparatively huge. One is the fossilized skeleton of a mastodon, an elephant-like animal that roamed North America until about 12,000 years ago. Even in pieces, the specimen is stunning, with a church-bell-sized skull.

Photo: John Schisler

Believed to be among the largest mastodon skeletons ever found, it was one of Andrew Carnegie’s first acquisitions for the museum and was on display until 2013, when the museum removed it to restore some of its bones. That conservation work was completed last year, and the mastodon now rests where Davis can keep an eye on it until it is ready for exhibition again. Lamanna hopes that day will come soon, especially after the museum’s recent $25 million dollar gift from longtime patrons Dan and Carole Kamin, part of which will be used to renovate the dinosaur exhibition and neighboring galleries.

Davis’ job is to ensure that each fossil is kept in the best shape possible—this includes checking that they are correctly identified, recorded in the museum’s database, and safely stored. Davis also helps other scientists use the collection, from fielding data requests to overseeing the use of a forklift to access large specimens.

Some of those large fossils are on a shelf near the mastodon. They are the manhole-cover-sized vertebrae of a dinosaur species whose initial discovery helped put Carnegie Museum of Natural History on the map: Diplodocus carnegii.

The first fossils of this sauropod were unearthed in an 1899 expedition funded by Andrew Carnegie. Later nicknamed “Dippy,” the famous dinosaur spawned casts that have been distributed around the world, and the original is still on display in the museum.

The Diplodocus fossils kept in the Big Bone Room, however, mostly don’t belong to that first find. Instead, they’re part of a second Diplodocus that was discovered in the same quarry the following year and used to fill in some missing parts of the specimen on display. That doesn’t mean they are any less significant.

“You could absolutely make a case that science has learned more from the second specimen of Diplodocus carnegii than it has from the first,” says Lamanna. That’s why a collection like this is so vital.

“It’s super important to have real fossils on display, but there’s a trade-off,” the museum’s longtime paleontologist continues. “Doing so tends to decrease access to the fossil for research. When we have specimens down in the collection, they can be studied, measured, photographed, and 3D-scanned from all angles. And that’s often how knowledge of paleontology advances.”

Dinosaur Color Theory

A drive for discovery is what brought Davis to the museum.

The Arizona native grew up the child of two scientists—an engineer and a pharmacist. She was drawn to paleontology as an undergraduate at the University of Arizona, where she pursued research projects on dinosaur appearance and color chemistry that she later built upon for her PhD thesis at the University of Texas at Austin.

“The research I did was into this pigment system called carotenoids, which are involved in the expression of pink, red, yellow, and orange, among other colors,” says Davis. “They are very tricky because they are unlikely to fossilize. What we find in the fossil record are melanin-based colors, which are black, brown, and gray.”

Photo: John Schisler

Davis turned to birds—descendants of dinosaurs—to examine how color may have been expressed in prehistory. Alongside her graduate adviser at UT Austin, Julia Clarke, Davis evaluated colors of more than 4,000 living bird species, as well as dinosaurs’ distant relatives, crocodiles and turtles, to determine the likelihood of carotenoid colors appearing in their extinct cousins.

She found that it’s possible that dinosaurs sported yellow, orange, or red skin features.

Lamanna was eager to learn more about Davis’ research after Clarke introduced the two of them. They worked together on Antarctic fossils, and Lamanna was impressed by her intelligence and enthusiasm.  

When the collection manager position opened, Lamanna thought of Davis right away. He figured the museum’s ornithological and paleontological collections would be an ideal professional home for her.

She agreed.

“This work is super rewarding,” says Davis. “I love being surrounded by fossils all day, and then also getting to do my own research.”

In With the Old and New

The collection manager job is a big one, and not just because of the size of its specimens. Davis is a steward to over a century of paleontological work, evidenced by the original tea-colored, cursive-written field notes still associated with many fossils.

Some notes are from a dig in Utah that helped build the foundation of the collection.

That excavation, begun in 1909, was led by Carnegie Museum paleontologist Earl Douglass. He was unearthing what would turn out to be the fossilized skeleton of a giant Apatosaurus when his team came upon the bones of another dinosaur, then another, and another.

Over 14 years, they collected 350 tons of prehistoric bones from that single locality, which today is known as Carnegie Quarry at Dinosaur National Monument.

“Much of what was there ended up here,” Lamanna says. “By most estimations, it’s the greatest single locality of Jurassic-age dinosaurs that’s ever been discovered anywhere in the world. It rocketed our museum into the stratosphere.”

The vertebrate paleontology collection continued to grow in size and scientific significance over the decades. More fossils came from digs around the world, including those in Egypt and Antarctica led by Lamanna.

Despite the allure of fresh-from-the-dirt discoveries, the oldest specimens can still yield great things.

Lamanna recalls a find made in the mid-1980s by Davis’ predecessor, Henrici. She was a preparator at the time, working on a hunk of rock from Dinosaur National Monument. It wasn’t believed to contain anything significant. But as Henrici chipped away the rock, she discovered one of the only lower jawbones of a Stegosaurus ever found.

“That’s why we hang on to this stuff,” says Lamanna. “New eyes come along, new technologies come along, new viewpoints and expertise. You learn new things from old stuff.”

Even a closer look at a well-known specimen can yield exciting findings.

Below the terrifying teeth of the T. rex holotype jaw are two or three gouges on its chin.

“We think this animal was nipped by another
T. rex at some point in his or her life,” says Lamanna. He points out how the surrounding bone shows signs of healing, indicating that the Cretaceous-era conflict occurred long before the dinosaur’s death.

“What’s awesome to me is that these show us evidence of two different animals and an interaction between them,” he continues. “It’s a literal moment  in time, captured for us to learn from 66 million
years later.”

Through that framing, the museum’s bone rooms are a trove of prehistoric stories, some told already, some still waiting to be discovered.

“This place is a library of the history of life on Earth,” says Davis. “The specimens are incredible on their own, but so are the people that built this collection. It’s amazing to be part of that history now, and to keep taking care of it for generations to come.”