MISSION VIEJO — Scientists say they have made significant discoveries among at least 3,000 fossils dug up in this area, including previously unidentified species of whales, crabs and fish.
The fossils, experts say, are 10 million to 15 million years old and confirm theories that the shoreline once extended from inland Camp Pendleton northeast to Chino and that Southern California once was a region of tropical temperatures.
"The new finds have the potential for resolving issues that we've been trying to address since the 1960s," said Dr. J. D. Stewart, assistant curator of vertebrate paleontology at the Natural History Museum of Los Angeles County.
The fossils were unearthed by paleontologists John Minch and Thomas Leslie, two Saddleback College professors whose San Juan Capistrano paleontological firm is monitoring excavation work on the Foothill Transportation Corridor.
The discoveries, Finch and Leslie said, indicate that hills now dotted by thousands of tract homes were once ocean beds frequented by sharks, whales and other marine life.
An Orange County ordinance and state law require that developers hire qualified archeologists and paleontologists to monitor construction likely to unearth fossils, said Laura Coley Eisenberg, an environmental analyst with the corridor agency.
Besides the fossil finds, experts have uncovered hundreds of tools and other items used by Gabrielino Indians.
For Finch and Leslie, the dig site turned out to be a paleontological gold mine. Among the finds were teeth of a never-before-discovered extinct type of whale.
Since excavation began in November, the paleontologists also have uncovered remains of sharks, sea cows and porpoises.
The paleontologists unearthed perfectly preserved avocado leaves as well as fossils of plants found today only south of the Mexican border, suggesting that Southern California once had the tropical temperatures of La Paz, Mexico.
The kelp and marine fossils prove that the area from Camp Pendleton to Chino--through Coto de Caza, Mission Viejo, Irvine and Tustin--was once under water. But during the past 15 million years, vertical movement of the earth has caused a general elevation of the West Coast.
Dr. Lawrence G. Barnes, curator of vertebrate paleontology at the Los Angeles County museum, said he collected 30,000 fossils, ranging from small fish and shark teeth to parts of camels, in the same area 10 years ago.
"The latest discoveries confirm that this area near Oso is one of the top 10 marine fossil-producing areas in North America," said Barnes.
The paleontologists' discovery of complete fossils of \o7 pseudoseriola\f7 , possibly a mysterious ancestor of the bluefish, was of interest to Stewart of the Natural History Museum. Stewart said he has found "bits and pieces" of the fish in Central and Southern California, but the latest discovery is probably the best specimen.
"If it could be determined that this fish existed" in both the Atlantic and Pacific oceans, "then something like weather conditions changed to make them extinct here," he said.
Minch and Leslie said some of their fossils are bound to generate interest from other scientists. "Some of the fossils, like the crabs," Leslie said, "are so new to us because there are no descriptions of them in the scientific literature. We are having to start from scratch."