Wall Street Journal, March 21, 2015
CHICAGO—After careful consideration, Tyler Keillor made a decision: T. rex had lips. In the debate over dinosaurs’ “oral margin,” one of the country’s top paleoartists has taken sides. Mr. Keillor’s job is to create “flesh models” of dinosaurs and other prehistoric animals based on fossil evidence—giving creatures that died millions of years ago a face, a story and sometimes lips.

Using traditional mediums like clay and resin, as well as CT scanning and 3-D printing, he is at the forefront of incorporating digital art and technology into paleontology.

Mr. Keillor works at the University of Chicago Fossil Lab under celebrity paleontologist Paul Sereno. His work, found in museum collections around the world, is often the public’s first look at a newly discovered species, as with the pebbly-faced predator Rugops primus, which was unveiled in 2004. “A plain fossil doesn’t look like a heck of a lot to the average person,” Mr. Keillor says.

Instead of studying science, he cut his teeth working in a dental laboratory, doing special-effects makeup and studying wig making at Chicago’s Lyric Opera. As a child, he “would try to make little puppets of the alien from ‘Alien,’ ” he says. He dropped out of college to work on low-budget horror movies, commercials and stage productions.

His skill set was well-suited to Dr. Sereno’s team. After another paleoartist struggled with the hair of a “7,000-year-old beautiful woman,” Dr. Sereno says, he turned her over to Mr. Keillor. “When you see it in the ground in the field, you need to have the mind and eye of an artist,” he says. “Paleontology is about envisioning things and bringing them back to life.”

On a recent Thursday, the soft-spoken Mr. Keillor, 42 years old, was painting orange silicone over pieces of a 95-million-year-old rib, the last of about 100 Spinosaurus bones he was reproducing for the University of Chicago before it repatriated the originals back to Morocco.

The Sereno team’s work on Spinosaurus, a carnivorous, semiaquatic theropod, was detailed in the recent Nova film “Bigger Than T. rex.” Among other reasons, the project is exceptional for being the first life-size skeleton produced from a three-dimensional digital model. Different sets of bones were scanned, resized and arranged to make a complete digital skeleton, with Mr. Keillor and the paleontologists filling in any missing bones using what Mr. Keillor calls “informed speculation.”

A computerized mill then cut the bones out of foam, which were molded and cast in resin. The 50-foot skeleton was mounted for exhibition in a swimming pose. Acme Design Inc., in Elgin, Ill., made the 5-foot skull. “It’s pretty wild, making something really old using new technology,” says Acme founder Clint Borucki.

The Fossil Lab’s next project involves 3-D printing the articulated, mountable skeleton of a birdlike dinosaur from CT-scanned fossils, which has never been done before.

Mostly, however, Mr. Keillor’s artistic decisions come from fossils and from studying dinosaurs’ nearest living relatives: reptiles and birds. He decided to give his Heterodontosaurus a fleshy protuberance over its nose like a turkey because of an indentation in the fossil skull. He also gave it a beak, fangs, molars, cheeks and fiendish-looking eyes. But he is quick to point out, “There’s a bone above the eye that makes it look evil. It’s not me, it’s the bone.”

Much of a paleoartist’s work is determining textures, colors and tissues not preserved, or barely preserved, in the fossil record. “I have to be able to justify every choice, every millimeter of the sculpture,” Mr. Keillor says. He concedes that he is willing to find “a feasible way to make the thing more visually interesting.”

His boss is emphatic about seeing “the balance and the beauty” in the animals his lab animates. (Dr. Sereno himself was named one of People Magazine’s 50 Most Beautiful People in 1997.)

“Usually, I give my dinosaurs lips,” Mr. Keillor says. “An animal living in an arid terrestrial climate would have had lips,” he reasons, pointing to carnivorous reptiles like Komodo dragons as living examples. But the oral margin remains controversial.

Thomas Carr, director of the Carthage Institute of Paleontology at Carthage College in Kenosha, Wis., is staunchly opposed. “If artists put lips on a dinosaur reconstruction I know that they’re doing so without any evidence to support that idea,” he says, “They’re simply not playing by the rules of rigor.” Dr. Carr considers birds and crocodiles, who are lipless, to be the only acceptable living references for dinosaur features. Reptiles like Komodo dragons are too distantly related, he says, “Dinosaurs are interesting enough that they don’t need to be sexed up.”

But Dr. Carr is a fan of showing dinosaurs in nontraditional poses, like the hulking yet subtle Dryptosaurus Mr. Keillor did for the Lake County Discovery Museum in Wauconda, Ill. It is a departure from what Mr. Keillor calls the “running, roaring cliché.” He portrayed it with eyes narrowed and mouth almost shut. “It looked like it was thinking,” he explains. He wants viewers to wonder, “Is this thing satiated and calmly looking at me, or is it about to eat me?”

While trying to decide on the proper skin for Rugops primus, which Dr. Sereno discovered in Niger, Mr. Keillor read technical papers about the animal’s nearest relative. He concluded that the texture was “an almost perfect match for a bag of dry lentils.” So he fashioned the creature’s pebbled, scaly skin out of lentils pressed into clay. For the skin of a little head-butting dinosaur, which is so new it has yet to be named, he used impressions from dried avocado skins.

“Tyler has a level of exacting detail and creativity that’s really remarkable,” Dr. Sereno says. Adds Mr. Borucki, of Acme Design, “You expect it to breathe, to blink.”

Whenever Mr. Keillor needs encouragement, he can turn to the roommates who inhabit the basement of his suburban Chicago home. Posed in a semicircle are nine cave man sculptures from the 1930s, discarded when Chicago’s Field Museum, where Mr. Keillor once worked, eliminated its beloved “Hall of Man” exhibit.

Details like the bloody knuckles on one of the cave men have a visceral narrative quality Mr. Keillor brings to his own work. The Keillors’ own 4-year-old son, meanwhile, prefers to stay upstairs.

“It’s like a painter owning a van Gogh,” says Tyler’s wife, Kari. “They’re part of the family.” Mr. Keillor took them to be appraised on the popular TV series “Antiques Roadshow,” but the experts didn’t see a market for 5-foot plaster Neanderthals. “I paid $75 each for the large statues, and I have a child that I paid $25 for,” he says. “I think I got a great deal.” When he has time, he plans to construct “a little bit of cave wall and a prop campfire with flickering lights so they’ll feel more at home.”

Lips aside, “He’s one of the best sculptors out there,” says Dr. Carr, who considers Mr. Keillor a master of realistic painting and scales. “Tyler has little competition at the present time,” he adds.

An example is his baby sauropod, just hatched from its egg, about to be eaten by a snake. Mr. Keillor made the diorama for the University of Michigan and is marketing a miniaturized version of it in “Prehistoric Times” magazine. The scene, discovered by paleontologist Jeff Wilson, was preserved in one fossilized moment. “I followed the bones and did what they told me to do,” says Mr. Keillor. Yet the pathos on the face of the little green sauropod is enough to melt the most rigorous of hearts.