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Drawing of a fossil preparator's hand excavating a juvenile Compsognathus dinosaur from rock, as the little dinosaur comes to life.

These essays about FossiLab projects first appeared as posts on the National Museum of Natural History's blog, National Museum of Natural History Unearthed.

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Planning a Barbecue in the Cretaceous Period
 
Six fossil vertebrae are still connected in a slab of rock.  They are in a paper plate, with a plastic knife and fork and a bottle of hot sauce at the ready.
Although they look a bit like spare ribs, these are fossil vertebrae that probably formed part of the tail of a marine reptile.

We have been thinking a lot about picnics and barbecues lately in FossiLab. Not only is it summer, but also a grill-worthy hunk of fossil marine reptile recently arrived in the lab. As a volunteer chips away at the rock matrix that covers the fossil, it looks as if a butcher’s cut of meat were appearing before our eyes, all ready for barbecue sauce. This South American fossil dates from the Cretaceous, and that got us wondering… if you were time-transported into the Cretaceous, say 130 million years into the past, and wanted to throw a summer party, what kinds of food could you serve?

If your idea of the perfect summer meal is a clam bake or a crab or crawfish boil, then you'd be in luck because shellfish, early lobsters, crabs and crayfish were already on the scene. Grilling would be an option, of course, but the menu would need some tweaking; dinosaurs and the early birds evolving from them might make chicken lovers happy, and there would be plenty of fish, but forget about pork and beef. The fossil record tells us that it wouldn't be possible to make pulled pork sandwiches until pigs evolved during the Oligocene (23-34 million years ago), and you'd have to wait until the Miocene (about 20 million years ago) for the bovids, the group that includes cattle, to appear.

The most serious meal-planning issues, though, would be in figuring out what to serve as side dishes and condiments. Fruits, vegetables, and most of the ingredients in barbecue sauces, salads, and breads all come from flowering plants, but this plant group (the angiosperms) was only just beginning to evolve 130 million years ago. So while your more adventurous friends might enjoy munching on seaweeds, fern fronds and pine nuts, summer essentials like watermelon, tomato salads and corn on the cob could not grace your table.

As for Cretaceous drink options, well, how would you feel about serving warm water? Ice tea, lemonade, beer and wine would be off the menu thanks to that not-yet-evolved-angiosperm problem, and finding ice would be very difficult -- the Cretaceous climate was so much warmer than today that a quick trip out for ice would turn into an expedition to the highest mountains of Antarctica.

In FossiLab, we think it would be awesome to visit the Cretaceous. But if we ever get invited to a Cretaceous barbecue, we will plan to pick up a few things at the market before we go.

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Dental Work, Anyone?  

For the last year and a half, a volunteer in the National Museum of Natural History’s FossiLab has been practicing slow motion dentistry on some amazing teeth. My dentist would be appalled by how long the job is taking, but she has never had to stare down molars this large or clean tartar buildup anywhere near as thick and hard as the rock matrix that’s hugging these monsters.

The teeth belonged to a brontothere, a type of mammal related to horses and rhinoceroses, that went extinct about 35 million years ago. They were preserved along with the upper jaw and part of the skull. The lower jaw is missing, as is most of the rest of the skeleton.

Paleontologists reported the first brontothere fossil discoveries in the 1870s. Since then, thousands of specimens have been collected in North America and Asia, allowing scientists to document the many ways that brontothere species changed over their 20 million years of evolutionary history. Early species were small and lacked horns, but some later species evolved to be as large as elephants and sported horns and other bony protuberances on their snouts that would make a modern rhino proud.

A long layover

Most FossiLab projects support the ongoing research of the Museum’s paleontologists, who explore fossil sites around the world. Even when collected in very remote places, the fossils usually arrive at FossiLab within a few months. The brontothere is unusual; its trip from South Dakota took more than 110 years.

In the early 1880s, Spencer Baird, the Smithsonian’s second Secretary, asked a Yale University professor of paleontology named O. C. Marsh to collect vertebrate fossils for the newly-built United States National Museum. A series of expeditions out west yielded a trove of Jurassic dinosaurs and Eocene mammal fossils that Marsh shipped to Yale for preparation and study. Eventually, a spectacular array of fossils, filling more than seven railroad cars, was sent to Washington. Included were dinosaurs, Stegosaurus, Allosaurus, and Triceratops among them, and more than 150 brontothere skulls. But the block of rock containing the FossiLab brontothere was overlooked and forgotten. So while the dinosaurs have been on display almost continuously since the National Museum of Natural History opened in 1910, and the brontotheres have been available for study in our collections, the FossiLab brontothere lingered in obscurity. The 1990s brought its rediscovery and shipment to Washington. Now, in FossiLab, it is making a slow motion debut.

Rock matrix is removed from the bones and teeth with small picks and a tool called an air scribe - a mini-jackhammer, really. The air scribe’s pointed tip makes high frequency impacts against the hard matrix, causing tiny bits of rock to fly off the chocolate-brown teeth and white bone. This speeds the work, but, still, progress is slow because enormous care is needed to avoid touching the tip to tooth or bone. Fortunately, the patient complains as much about the slow pace of cleaning as it does about the century-long wait for its dental appointment, which is to say, not at all!

A lifelike painting of a brontothere.

This painted reconstruction of a brontothere is from an NMNH mural by Jay Matternes. It is located in the Mammals in the Limelight Hall.

The tips of dark brown brontothere teeth protrude in two rows from a large block of white rock matrix.

The block of rock containing the brontothere skull, as it appeared the day we started work. The skull is upside down and the upper teeth are partly visible.

The brown teeth have largely been uncovered, and a lot of white bone has been exposed.

One and a half years later, the protruding cheekbones have been uncovered on the left and right, more teeth are visible, and the jaw bone is partly exposed below the teeth. Bone toward the back of the skull has been uncovered in many places.

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Fossil Hunting under the Watchful Eyes of Lions  
   

The Museum's fossil preparation facility, FossiLab, recently received a shipment of dinosaur fossils from northern Zimbabwe.  They were collected last year by an international team of scientists, including NMNH Dinosaur Curator Matt Carrano.

The fossils, still largely encased in rock, are of two types of dinosaur.  One, a small, primitive meat eater closely related to Coelophysis, was a member of the dinosaur group that eventually gave rise to huge predators like T. rex.  These fossils were found in a "bone bed," a place where the fossil remains of many individuals are mixed together.  Coelophysis fossils have been found in other bone beds, most famously at Ghost Ranch in New Mexico, and the new discovery may help scientists answer questions such as whether Coelophysis and related species lived in groups, and what events led to the death and burial of so many animals at once.  The other Zimbabwean dinosaur is a prosauropod, a medium-sized plant eater that had a large claw on its thumb, a long neck, and leaf-shaped teeth for chopping plant matter.  They seem to have been quite common at a time when the local environment was desert, and researchers wonder why.

The scientists discovered the fossils in a river canyon.  During the rainy season, water courses through the canyon eroding its rock walls and uncovering fossils.  Then, when the rains stop, the riverbed dries up and becomes a convenient path for scientists prospecting for newly exposed fossils – and for lions and elephants traveling through the bush.

Paleontologists are friendly, as a rule, but prospecting can be solitary work.  Team members often spread out to cover as much territory as possible, and as they walk slowly along searching for fossils, they sometimes become oblivious to everything around them.  Obviously, this is not the smartest behavior when large, possibly dangerous animals are nearby, so the team hired a local wildlife guide to keep them out of trouble.  He coached them on what not to do when charged by lions (run), or elephants (stand still) and kept them bunched together in the relative safety of a "herd" as they prospected in the canyon.

The scientists found the tracks of several big cats as they worked in the riverbed, but, to their relief, they came face to face with only one group of predators -- dinosaurs, all safely fossilized.

An opened field jacket containing many fossil bones

At the Museum, a plaster and burlap field jacket holds a jumble of dinosaur fossils from the bone bed, including a jaw fragment with teeth (center).

Cutting blocks of fossil-containing rock out of the bone bed exposed on the canyon wall

Removing fossils from the canyon wall in Zimbabwe.

leopard tracks in the dry river bed

Leopard tracks in the dry riverbed.

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Tiny Fossils, Big Excitement  
   

Visitors to FossiLab, the fossil preparation laboratory in the ancient life halls of the Museum, see work that normally goes on behind the scenes at museums. They watch specially trained volunteers prepare fossils for scientific study, display, or storage in our enormous collections, and sometimes they witness exciting discoveries.

Most of the fossils we work on in FossiLab were found and excavated by Smithsonian paleobiologists (scientists who study ancient life), whose research takes them to remote places around the world. When the packing crates containing their discoveries arrive in FossiLab, we pull out our tools and get to work. Right now, we are cleaning T. rex foot bones, the skull of a brontothere (an extinct relative of horses and rhinos) embedded in a massive block of rock, and a couple of whale skulls. Removing all the rock from these behemoths is interesting and fun, but we often wish we’d been there when the fossils were discovered -- wouldn’t it be cool to be the first person to see something that had been buried in the earth for millions of years! That’s why we get so excited when we open a crate and find bags containing loose bits of broken-up rock, not "just another" T. rex bone. The lumps of sedimentary rock, or "matrix," offer a chance to make fossil discoveries right here at the Museum!

When scientists go out prospecting for fossils, erosion is their best friend. Most of the “life” of a fossil is spent deep underground, encased in rock, and it is only after erosion slowly breaks apart the rock matrix covering it that a fossil can be discovered. Scientists searching for the fossil remains of big animals walk along eroding hillsides and look for bones protruding from the earth or for telltale bone fragments at the bottom of a slope. If they spot something that looks interesting, they remove the loose matrix and carefully trace the remains back into the hill, hoping to find more bone entombed in the rock.

But paleobiologists don’t always go for the big stuff. All fossils provide important evidence about the history of life, ancient ecosystems and environments, and for some research, finding the fossils of tiny creatures becomes Job #1. Prospecting for small fossils requires enormous patience and keen observation, and some people are really good at spotting bits of tiny bones and teeth eroding from the same outcrops that hold the fossils of larger animals. That is when shovels fill canvas bags with as much broken-up matrix as the scientists can carry, and crates full of matrix make their way to back to the Museum.

In FossiLab, we have time to do a more thorough search of the crumbling matrix. We use a microscope so that we can see even the tiniest bones and teeth, and we don’t have to contend with the dripping sweat, too-bright sunshine, blowing dust, and cramped muscles that make it so difficult to spot small fossils out in the field.

Lately, we have been looking through matrix from Petrified Forest National Park in Arizona, finding the pencil tip-sized teeth of very small reptiles, and even fragments of dinosaur teeth. This matrix was collected last spring by Museum paleobiologist Dr. Kay Behrensmeyer and her colleagues. The goal of their expedition was to find fossils of mouse-sized early mammals and evidence of the environments where they lived during the Late Triassic Period, more than 200 million years ago. Although the area was once wet and green, there is no water there today. The eroded badlands are so rugged, and the fossil-bearing rock outcrops so far from the road, that they had never been explored by paleontologists. Kay’s team solved the challenge of setting up camp near the outcrops by hiring Navajo wranglers from a nearby ranch to transport their gear and water on pack horses and mules. The scientists prospected and collected on the outcrop for nearly a week, and when the wranglers returned to help them pack out, bags of matrix began the journey to FossiLab tied to the saddle of a strong black mustang.

Now, new bits of interesting teeth and bones turn up regularly under the FossiLab microscope, while Museum visitors follow the fossil search in real time on a large TV screen. So far we’ve found no mammal fossils, but the other tiny teeth are providing lots of clues about life in Arizona during the Triassic – and the thrill of discovery at FossiLab.

A man riding a horse leads a pack horse loaded with bags of camping gear across rough terrain.

The fossil sites were in remote and rugged terrain, so the scientists' gear was transported by pack horses and mules.

A student kneels on the ground and peers closely at it, looking for small fossils.

Searching for small fossils in loose matrix.

A FossiLab volunteer uses a microscope to search for tiny fossils in the lab.

In FossiLab, we use a microscope to search through the Petrified Forest matrix.

A fragmentary fossil of a toot with serrated edges.

A minute tooth fragments discovered in FossiLab.

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