California researchers have discovered four new legless lizard species, raising the total number of known legless lizard species to five.

The researchers realized the specimens they were studying were legless lizards, not snakes, because they were able to lose their tails in the presence of predators and close their eyes — characteristics not displayed by snakes.

The lizards can grow to 10 inches in length and are thinner than a pencil, according to Theodore Papenfuss, a research scientist at the Museum of Vertebrate Zoology at UC Berkeley. He began the study in 1998 and later was joined by James Parham, an assistant professor of geological sciences at California State University at Fullerton and a faculty curator of paleontology at the John D. Cooper Archaeology and Paleontology Curation Center.

Researchers placed more than 3,000 pieces of cardboard and plywood across the western coast and Central Valley of California to attract the lizards, which are likely to be found burrowing in loose, sandy soil.

“It’s a huge amount of effort, both physical effort, planning and logistical effort,” Parham said. “We didn’t expect to discover four new species.”

The new species were discovered in four places across California: in Bakersfield, at the end of a runway at the Los Angeles International Airport, in the extreme southwest of the San Joaquin Valley and in canyons on the western edge of the Mojave Desert.

The lizards found in Bakersfield have purple undersides, whereas those found in the Mojave Desert have yellow undersides. The species found in the southwest San Joaquin Valley have silver-gray undersides and more vertebrae, and those found at the Los Angeles International Airport have fewer chromosomes, indicating they will have greater difficulty reproducing.

“The legless lizards seemed to be an obvious species to study because, based on the types of places they like to live, which is sandy soil, they don’t occur everywhere,” Papenfuss said. “They occur in pockets around the state.”

The lizards are classified as “species of special concern,” meaning they are not yet considered endangered but may be at risk. They require careful monitoring, Papenfuss said.

Papenfuss and Parham named the species after UC Berkeley scientists Joseph Grinnell, Charles Camp, Annie Alexander and Robert C. Stebbins to honor their contributions to natural -history research, the development of museum science and generous donations to and directorship of the Museum of Vertebrate Zoology at UC Berkeley.

With the release of the study, Papenfuss hopes the new species can raise awareness of growing biodiversity and encourage people to set up more reserves protecting these species.

“Our goal now is to learn more about the distribution of these forms,” Parham said. “It’s logical if something has a small distribution, it’s more likely to be wiped out by human impact.”