Twenty-nine species in more than 20 states — from a rare beach-dwelling plant in Yellowstone National Park to a caddis fly in Nebraska — may need federal protections to avoid extinction, according to the U.S. Fish and Wildlife Service.

The agency said Tuesday that 20 plants, six snails, two insects and a fish may warrant protection under the Endangered Species Act but in-depth studies are needed first.

The decision is a response to a 2007 petition by WildEarth Guardians, an environmental group that sought protections for more than 200 species, most of them in the West.

In February, the agency turned down protections for 165 plants and animals and delayed a decision on the remaining 38.

Among the 29 that federal officials said may need protection are the Yellowstone sand verbena, which only lives on the sandy beaches of Yellowstone Lake, several species of milkvetch in Wyoming, Utah and Colorado, and a Midwestern mollusk called the Frigid ambersnail.

Fourteen of the 29 appear in Utah, including 10 plant species and a small silvery minnow called the Northern leatherside chub.

Diane Katzenberger, a U.S. Fish and Wildlife Service spokeswoman in Denver, said each of the species will now get a detailed review, including identification of its range, distribution and threats.

Federal officials will then decide whether each needs to be protected as a threatened or endangered species.

Nicole Rosmarino, wildlife program director for Santa Fe, N.M.-based WildEarth Guardians, said she's pleased with the decision but more needs to be done to protect other species deemed threatened by scientists.

"To catch up with the biodiversity crisis in the U.S., the service needs to be listing dozens of species at once," she said.

The Fish and Wildlife Service defines an endangered species as one that is in danger of extinction throughout all or a significant portion of its range. A threatened species is one that is likely to become endangered soon.

The agency said several of the 29 species being considered for protection could be affected by climate change, including the meltwater lednian stonefly that's only been found in Montana's Glacier National Park. The loss of glaciers in the park by 2030 — as predicted by some scientists — could jeopardize the fly's habitat, the agency said.

Other species face threats from habitat loss, road construction, mining, livestock, energy development, off-road vehicles and water diversions, the agency said.

Nine species were denied the possibility of federal protections because there wasn't sufficient information in the petitions.