Josh Bonde, a geoscience teacher and paleontology research associate at the University of Nevada, Las Vegas, said in a brief telephone interview that the fossilized backbone vertebrae come from a layer of rock some 220 million to 230 million years old.
There's no positive identification yet, but Bonde told the Las Vegas Review-Journal that the fossils found at Spring Mountain Ranch could predate 190-million-year-old dinosaur footprints spotted in 2010 in nearby red rock sandstone.
He said the bones might have belonged to a phytosaur, an early ancestor of the crocodile, or a metoposaur, a giant amphibian with a broad, flat, triangular head.
"It's something big," Bonde said. "These are great big vertebrae."
The animals would have lived when present-day Nevada was covered by a shallow sea and populated by the ichthyosaur, a marine reptile as big as a school bus that is now Nevada's official state fossil.
Bonde said a search team found more fossilized bones and fragments during the weekend in the area where Harold Larson, an 84-year-old retired civil engineer, found the first odd-looking rock specimen a few months ago.
Larson, a Las Vegas resident since 1954, told the Review-Journal that even his friend, Nick Saines, a geologist and naturalist for the Red Rock Canyon Interpretive Association, didn't believe at first the rock he found was a fossil. The nonprofit association helps the federal Bureau of Land Management operate Red Rock Canyon National Conservation Area.
State park workers later found two more fossilized vertebrae in the same general area.
"The moral of the story is if you believe something, you gotta keep working at it," Larson said.
Bonde has been hunting old bones in Nevada for a decade, and played a role in discoveries ranging from 300 million-year-old dinosaur fish in central Nevada to an ice age wolf in the hills north of Las Vegas.
He said the new find comes from the same layer of rock as fossilized logs found at Valley of Fire State Park northeast of Las Vegas and Petrified Forest National Park in eastern Arizona.
Russ Dapsauski, southern regional manager for the Nevada Division of State Parks, said any fossils from Spring Mountain Ranch will go to the Las Vegas Natural History Museum for study.
Fossils found on BLM land are collected and studied at California's San Bernardino County Museum.
Dapsauski said the exact location of the Spring Mountain Ranch find was being kept confidential to protect the sensitivity of the site.
Information from: Las Vegas Review-Journal, http://www.lvrj.com