Ancient whales:
Fossil hunters find bones of species that swam in the sea some 5 million years ago.
The fossil hunters of the Purisima Formation are avid collectors of the dead — they probe the beaches and sandy cliffs around Santa Cruz to find the stony bones of birds and whales and sea creatures that lived and died there millions of years ago.
To scientists, those amateur hunters provide an endlessly renewing source of material that bears witness to the ebb and flow of evolution as environments change over the millennia and life adapts to the changes and moves on into ever-new forms.
Two of those amateurs recently passed on a few of their trophies to Robert W. Boessenecker — known as Bobby to his surfing friends in Capitola — who is now a 27-year-old paleontology graduate student in New Zealand.
Evolutionary ancestors
He and two colleagues have just published a scientific report on the fossil discoveries: a primitive whale skull and two ear bones from two members of the dolphin family that swam in the sea some 5 million years ago and appear to have shared the features of modern whale species. The ancient animals might well have been the common evolutionary ancestors of their modern descendants, Boessenecker believes.
His detailed description of the primitive bones is published in the international paleontology journal Acta Paleontologica Polonica. In the report, Boessenecker credits Stanley Jarocki of Watsonville and Robin Eisenman, a one-time Aptos beachcomber, as the fossils’ finders.
Probing the cliffs
Jarocki, now retired from construction engineering and a longtime Santa Cruz surfer, has been probing the nearby cliffs and beaches for more than 30 years — both to add to his own fossil collection and to give away to eager scientists.
“In this fossil-hunting business they say that what you find is yours, but I’m just a hunter and a donator,” Jarocki said. “I remember that I once gave Bobby some fossil bird bones I found, and he studied them, and this time I gave him the ear bones I found embedded in the cliffs that I didn’t really need.”
Jarocki also donates many of his finds to the Santa Cruz Museum of Natural History, where he is a valued contributor to the museum’s fossil collections, said research associate Frank A. Perry, a co-author of Boessenecker’s report.
“He donates lots of small stuff he finds and that other fossil hunters overlook,” Perry said. “I first met him 20 years ago, when he donated a whole collection of early shark teeth that dated from 10 or 12 million years ago.
“They were the inspiration for an entire report on the sharks of that era that the museum published.”
Robin Eisenman, who found the ancient whale skull on a beach north of Aptos, has since reportedly left to live in Idaho, where the ocean is more than 600 miles away.
The beachside fossil hunters working around Santa Cruz are vital to his research, Boessenecker said, and that’s how he met Jarocki five years ago.
“You’ll see people with their kids, walking their dogs, people surfing, and occasionally someone who’s paying a bit too much attention to the rocks, standing out like a sore thumb as a fossil collector,” Boessenecker said. “So I went up to introduce myself and we chatted.”
Fossil-rich area
The result was Jarocki’s gift of the fossil ear bones that, like Eisenman’s fossil skull, came from animals long buried in what geologists term the Purisima Formation.
It’s a series of fossil-rich sandstone outcrops along the coast, from Point Reyes to the Santa Cruz area, that were thrust upward by earthquakes some 7 million to about 2.6 million years ago, when the Pacific Ocean reached into what is now the Central Valley.
Surfers have long discovered fossils in the cliffs above the beaches in the Santa Cruz area, and Boessenecker is both a surfer and a fossil hunter.
Now a graduate student at the University of Otego in New Zealand, he has teamed with Perry in Santa Cruz and with Jonathan Geisler, a mentor at the New York Institute of Technology’s College of Osteopathic Medicine in Old Westbury, N.Y., for his report on the Purisima Formation’s ancient whales.
Bones a bit of a mystery
The fossil bones are something of a mystery; there are too few to link them precisely to any modern whale species, Boessenecker said. But they clearly come from a group known as Globicephalines — otherwise known as blackfish — that include pilot whales, false killer whales and some dolphins, he reports.
“The fossil skull shares features with both pilot whales and false killer whales and may be the common ancestor to both,” Boessenecker reported. “They probably would have lived in environments like the modern California shelf and Monterey Bay of the Purisima Formation.”
Says Perry of the mystery that remains about the fossil whale bones:
“I see the study of fossils akin to assembling a gigantic jigsaw puzzle. Little by little paleontologists collect and put together the pieces, giving us a better picture of the past. We’ll never have the entire picture, but every little part helps.”