Treasure unearthed at Field

Rumors circulated in the nation’s paleontology laboratories for the last several months that the Field Museum had found a valuable dinosaur fossil, a cousin of Tyrannosaurus rex.

It had–in one of its own storerooms.

The fossil in question is known only as 51-22, a code for it being the 51st specimen collected on the Field’s dinosaur prospecting expedition in Alberta, Canada, in 1922.

It is the 70-million to 75-million-year-old partial skeleton of a very young tyrannosaurid, the family of huge, two-legged meat-eaters.

“It’s a fairly significant fossil because of the stage it’s in in its life cycle,” said Peter Mackovicky, the Field’s resident dinosaur expert, who said he will begin scientific work on the bones later this year.

Field officials say they are not embarrassed about the 80-year oversight. Finding hidden treasures in enormous natural history collections like the Field’s, which has 21 million artifacts and specimens in its storage bins, is not all that uncommon, though few in-house finds are quite as good as this one.

When museums go on collecting expeditions, they always try to come home with more material than their scientists have time to study. The idea is material that doesn’t get studied today will always be preserved for future study.

In recent years, scientists have hauled out of storage ancient corncobs found in a cave to gain insights into early agriculture. And a richly carved plaque that had been in storage for decades has suggested for the first time that pre-Columbian nobility in the Americas might have swapped gifts.

With more powerful research tools and new theories of natural and cultural evolution, pack-rat wisdom has proved itself over and over.

With that in mind, the museum stored gunnysacks filled with rock chipped away two years ago from the Field’s great Tyrannosaurus rex fossil. Someday, said Bill Simpson, the museum’s chief fossil preparator, somebody will be assigned to go through the detritus of Sue with a microscope.

“We know it is filled with microfossils of pollen and things like frog, lizard and mammal teeth that will explain a lot about Sue’s world,” Simpson said.

With 21 million objects to look after, there aren’t enough scientists to go around to study and know each object individually.

Eventually, though, old finds rise to the surface. Mackovicky will be working with the almost perfectly preserved rear end of specimen 51-22–probably an Albertosaurus–including its complete 8-foot tail and right leg and foot, and almost-complete left leg and foot. Most of its torso is missing, as is most of its skull.

“It is not even half-grown, so it gives us a good idea of what an Albertosaurus child would have looked like,” Mackovicky said. “It is going to tell us some things we don’t know about the growth cycles of these kinds of animals.”

The fossil was discovered in Canada by Elmer Riggs, the Field’s pioneering paleontologist hired in 1898 to find spectacular dinosaur fossils for display.

Though he was more interested in fossil mammals, Riggs did not let the museum down. He soon brought back some of the great dinosaur fossils in history, including the biggest, Brachiosaurus–a life-size, 90-foot model of which now stands in O’Hare International Airport–and an Apatosaurus and Triceratops that the museum still displays.

In 1922, he and his crew were digging up fossilized sequoia trees, turtles, freshwater clams, leaves and skeletons of dinosaurs found in rock 70 million to 75 million years old.

They encased each rock-encrusted fossil under protective layers of white plaster, called field jackets, and placed them in dozens of wooden crates for shipment to Chicago.

Specimen 51-22 was large enough to take up an entire crate. Riggs was unsure of what it was, noting on one manifest that it was a “partial skeleton of a carnivorous dinosaur” and put a question mark over the word carnivorous on another manifest.

When the shipment reached Chicago, museum officials had only one of the dinosaur fossils undergo the expensive, time-consuming process of removing the rock from the fossilized bones.

The one selected was a mostly complete skeleton of a duckbill dinosaur, a fossil now on display in the museum’s Life Over Time exhibit hall.

The rest of the dinosaur remains brought back, however, were packed away in storage bins, still in their plaster field jackets, including specimen 51-22.

“We still have the other dinosaur fossils from that trip in field jackets,” Simpson said.

“Every now and then, I replaster the outside of the field jackets to make sure they remain secure,” he said. “Through all those decades they have been here, somebody has always been aware of their existence here, though it might have been only one person, like myself.”

Through much of its 109-year history, the Field Museum was never very interested in dinosaurs.

Riggs’ early dinosaur finds attracted tremendous crowds 100 years ago, when public interest in the prehistoric beasts was at least as rabid as it is now. But that interest was waning by the 1920s, and the museum stopped looking for new dinosaur fossils. In fact, it never had a dinosaur specialist on its staff until it hired Mackovicky last year.

More Top Picks Dual Batterys

“For much of the last century, dinosaur science was not highly regarded by most paleontologists, who were more interested in paleomammalogy,” Simpson said.

In the late 1960s, there was a reawakening in dinosaur interest, both on the part of the public and with scientists. It turns out that dinosaur fossils are rich sources of information on a broad spectrum of topics, such as evolution, continental drift, climate change and extinction events.

Now, Simpson said, we are living in the middle of the golden age of dinosaurology. Public interest in the topic seems insatiable, and most of the best young minds in paleontology seem to gravitate to dinosaur research.

“Two-thirds of the known dinosaur species have been discovered in the last 20 years,” Simpson said.

Someday, he said, once Mackovicky’s work is done, it might be possible to find enough portions of skulls and torsos of younger Albertosauruses in other museum collections to make a composite skeleton of the youngster for display.

As for Riggs’ other 1922 dinosaurs still in storage, they likely will stay there for a long time, Simpson said.

Most of them are fragments of duckbill dinosaurs, the most commonly found dinosaur species, so there is no need to prepare them.

“Beyond dinosaurs, we have far more fossil mammals still in their field jackets, still in storage and never looked at,” Simpson said. “They are of animals we think we already know well from the fossil record.

“But what seems uninformative today may be something that turns out to be extremely valuable in the future as powerful new ideas and research tools–not yet invented–come into being.

“That’s why we rarely throw things away. We’re good at taking care of things for a long time. It’s what we do.”