Fossils of huge aquatic lizard discovered in San Joaquin Valley

In a laboratory at California State University, Stanislaus, a researcher is carefully extracting from a hunk of shale the fossilized remains of what appears to be a giant aquatic lizard. At least 65 million years old, the lizard hails from a time when ocean waves crashed against the Sierra foothills.

For the last three months, Susan Bowman has been gently disassembling what began as a 400-pound block of shale found in the Panoche Hills of western Fresno County. A research intern with the US Bureau of Land Management and a CSU Stanislaus graduate in anthropology, archeology and paleontology, Bowman has removed and cataloged 28 fossilized vertebrae, rib fragments and flipper bones. At first glance, they appear to belong to a species of long-necked undersea carnivore known as a plesiosaur.

Plesiosaurs have been described by scientists as similar to a snake strung through a turtle’s shell – though they did not have shells - with a long neck, short tail, broad body, and four flippers The biggest may have been more than 60 feet long, making them the size of sperm whales and possibly the largest predators of all time.

“More research needs to be done before we can positively identify the fossils as plesiosaur,” Bowman said. “We are hoping that there are enough of the partial fossils to be able to identify the specimen positively. I will also be studying the fossils of invertebrates in the sediment surrounding the larger fossils to learn more about the environment in which the animal died.”

The Panoche Hills west of Interstate 5 near the small town of Firebaugh have yielded fossilized remains for the past 90 years. Bureau of Land Management natural resources specialist Ryan O’Dell describes the region as, “a long strip of purple, white and brown-colored badlands in rolling terrain of otherwise grassy foothills.” Excavations there have led to the discovery of the fossils of several new species, including sea turtles and serpentine marine reptiles called mosasaurs.

“In the late Cretaceous period, California’s coastline was 120 miles further inland than today and the Coast Range was a string of islands,” Bowman explained. “The remains of sea-dwelling organisms were swept against the east side of the Coast Range, sank to the ocean floor, became buried by layers of sediment, and were fossilized.”

The story behind the fossils in the CSU Stanislaus laboratory began last summer, when O’Dell discovered them on a steep slope while surveying the Moreno shale formation in the Panoche Hills. After minor excavations with his crew, including Central Valley paleontologist Chad Staebler and BLM intern Kelly Bougher, O'Dell brought on Bowman in March, to assist with the excavation of the final block and was joined by Julia Sankey, a professor specializing in vertebrate paleontology at the Department of Physics, Physical Sciences and Geology at CSU Stanislaus in Turlock. The team created a plaster jacket that encased the fossilized remains so they could be transferred to CSU Stanislaus for Bowman to prepare the fossils in the lab.

“This was challenging field work because the fossils were in a steep cliff face and we had to watch for falling rocks all the time,” said Sankey, whose research includes a focus on the mass extinction of dinosaurs 65 million years ago.

Bowman, who took coursework under Sankey, is hoping to return at some point to the Panoche Hills to see if any more of the creature can be found.