They draw fantastic creatures that no one has ever seen, based on scraps of ancient bone and scanty threads of information. And their critics? Merciless experts they don't even know.
Yes, illustrating dinosaurs and other prehistoric life can be a challenging job for an artist.
"Most of the public is looking at the pictures. That's why their work is so important," said James Kirkland, a Utah State paleontologist and member of a team that recently discovered a new dinosaur species.
Paleontologists like Kirkland spend years digging in sun-baked wastelands, pawing through fossil remains in search of prehistoric life. But when they make a discovery, they need artists to create images that will grab the public's imagination.
"I feel like I'm acting as a representative of the dinosaur because it can't speak for itself," said veteran dinosaur illustrator Michael Skrepnick.
Kirkland and colleagues announced their discovery of Falcarius utahensis with help from Skrepnick, who brought to life a beast that thrived 125 million years ago, bridging a gap between meat-eating predators and later herbivores. And his images attracted public attention that the researchers consider vital for financial support for their work.
"We're one of those sciences where there's an artistry that can be tied to the public's reaction, as opposed to chemistry or maybe physics," said Lindsay Zanno, a co-discoverer of Falcarius.
Illustrations of prehistoric animals in journals, museums and even in the movies create indelible impressions. It's the artist who creates a dinosaur's personality, be it a friendly, loping vegetarian or a fierce predator. Either can remain etched in our memories: think of the Velociraptor that chased children in Jurassic Park.
"As someone in my 40s, I grew up with the image of dinosaurs as dull-witted, swamp-dwelling behemoths. But for the generation since Jurassic Park, there's an image of a fiercer, more predatory, fast-moving beast," said Lawrence Witmer, a dinosaur expert and anatomy professor at Ohio University's College of Osteopathic Medicine.
Some illustrators spend months or even years on a project, creating models out of clay or wire frames before they begin sketching. They do their own research, consulting experts and going through dozens of pencil sketches before committing to a color illustration.
"It's really important to study the creature and the environment that it lived in," said Kazuhiko Sano, an illustrator whose work has appeared in Scientific American, National Geographic and several international publications.
Sano makes clay models of the creatures he sketches and daydreams about them to trigger his imagination as he tries to give them a personality.
He also studies information about them -- their diet, how they moved and captured prey -- to try to bring them to life for viewers. It helps that he's been fascinated by dinosaurs since childhood.
"I go through a daydream in my head to try to make these creatures come alive," he said.
The results can be striking. Sano's cover for a Scientific American in 2003 shows a newly discovered, feathered dinosaur that looks ready to launch an attack. His illustration of a hobbit-sized Indonesian hominid on the March Scientific American cover shows a lean and muscular male looking up at the viewer, a spear in hand and a threatening look in his eye. The perspective was intentional.
"The problem was, how do you show that this human was really little without bringing in anything else to show scale? It accomplishes that by having him looking up from a lower perspective," said Jana Brenning, senior associate art director at Scientific American and a former free-lance illustrator.
The artists have different reasons for pursuing careers -- or parts of careers -- drawing dinosaurs.
Sano, who also paints landscapes, movie and opera posters and book covers, began drawing dinosaurs in the early 1990s to keep from burning out. Variety, he says, is a key to a productive career in illustration.
"If you're painting just people or just book covers or period pieces, you can get tired of them. Doing different things makes you more excited about doing them," he said.
Skrepnick, whose image of a snarling Falcarius appeared in newspapers and magazines across the country, is more of a dinosaur specialist. He's been drawing the ancient beasts since he began working as a volunteer at a Calgary museum in 1985. His work has also appeared in National Geographic and at the Field Museum in Chicago.
In the case of Falcarius, the illustrator was lucky: Researchers had 90 percent of the creatures' bones. All too often, paleontologists and their artist collaborators have only fragmentary evidence to go by.
"The more you have to work with, the better off you are," Skrepnick said.
When researchers have just a few bones or fragments, they use the creature's nearest relative as a model. They can usually place an ancient creature into its dinosaur family with just a few bones.
"It's not much different than if someone works with cars and picks up an engine or an axle -- they can tell if it's a Ford or a Chevy. If you have an isolated thigh bone, you can tell just about every animal on earth," Kirkland said.
Different bones also hold different clues. Limbs and the vertebrate, for example, are indicators of overall body size and can show how a creature walked or ran. Joint size can be a clue to body weight. The skull is critical in determining brain size, while teeth, jaw size and chewing muscles can show what an animal ate, said Christopher Ruff, director of the Center for Functional Anatomy and Evolution at the Johns Hopkins School of Medicine.
In some cases, limited information has led to mistakes.
The British anatomist who coined the term dinosaur, Richard Owen (1804-1892), was responsible for putting a spike on the nose of an Iguanodon, a primitive dinosaur, when it was portrayed in a sculpture at the British Exhibition of 1851. The spike was a bone that turned out to be part of the animal's hand.
Early sketches of one of Kirkland's discoveries, a clawed meat eater known as Utahraptor unearthed in 1993, had to be redrawn years later because the animal turned out to have legs that were shorter and designed more for power than distance running.
"It turned out to be more of a pit bull than the greyhound we once thought," he said.
As a result, scientific illustration is part art and part science. The accuracy of the finished product -- whether it's helping sell a science fiction novel or a scientific study -- depends on the artist and medium.
"There's always a tension between scientists who want to be conservative and artists who are creative by nature and want to be detail-oriented," Witmer said.
Witmer sparked a controversy in 2001 when he published a study in Science concluding that the nostrils of dinosaurs were near the tip of their snouts, not higher up and closer to the eyes, as had been widely thought.
That prompted heated discussion in scientific journals about a thorny subject -- what dinosaurs actually looked like. The bottom line: The further back you go, the fewer fossils there are and the less certain experts can be, Witmer said.
"When you're talking about T. rex, we know about the bones and the overall structure. But we don't know the details of what these creatures looked like fleshed out. Did they have big noses or little noses? What about their color or complexions? Did they have body hair? These things are going to be more speculative," Witmer said.
Artists labor under a range of deadlines and use a variety of methods. Sometimes, they work like police sketch artists, creating a quick image based on descriptions from a scientist who may have only a few fossils or bone fragments.
Payment rates at most magazines range from $2,000 to $10,000 per assignment. Just getting work on a magazine cover is a major achievement.
At National Geographic, every illustration goes through a series of reviews by three scientific experts before publication, said Christopher Sloan, the magazine's art director. There are similar reviews at Scientific American, where illustrations accompany articles written by scientists. Accuracy is a must, the editors say.
"Our readers are just sitting out there, waiting to pounce," said Scientific American's Brenning.
But whenever an artist has to deal with prehistoric life forms -- such as an extinct race of 3-foot-tall Indonesian hobbit people -- some artistic license is inevitable.
"We don't know what the skin coloring was of ancient humans, what their hair covering looked like or what their eyes might have looked like. You could call it artistic license, but in many cases, it's more of an educated guess," Sloan said.
Sometimes, illustrations get ultra-complicated.
To portray a 400 million-year-old Canadian landscape for a future exhibit, Smithsonian Institution illustrator Mary Parrish exchanged more than 65 e-mails with scientists to nail down details about the color of the vegetation, the contours of the land and the diversity and patterns of plant life.
Much of the discussion focused on an extinct fungus known as a prototaxite -- which could grow to heights of 25 feet -- and whether it should stand upright or on its side.
"Making a beautiful painting is difficult, even when copying directly from nature. Add to that the complications that come with building a reconstruction based on fragmentary fossil remains and verbal description from the scientist, and an artist has a real challenge," Parrish said.
The Smithsonian opened a Web site last month that focuses on the techniques used in paleontological illustration. Information: www.nmnh.si.edu / paleo / PaleoArt / .