In 2021 postdoctoral researcher Kumiko Matsui was looking through the fossil drawers at the Smithsonian National Museum of Natural History. In one she found a strange brown tooth, a large molar measuring over two inches long, that was once held in the jaw of an extinct seagoing mammal.
Long before early humans first walked the shorelines of northern California, in the surf this huge creature used its shovel-like jaws to scoop up seaweed, and its molars to macerate it, much like the dugong. It probably looked a little like a tusked hippopotamus. Living at the dawn of the modern Miocene geological epoch, about 22 million years ago, humans never saw them. But we’ve given them a name – Desmostylus – after the shape of its molars.
Matsui’s find was almost accidental, since the tooth had no exhibit number – just a few handwritten notes. They told her and her co-researcher Nicholas Pyenson that a U.S. geological survey expedition had collected it in northern California’s Schooner Gulch geological formation.
Schooner Gulch is one half of one of the strangest coastal parks in California. From a parking area on Highway 1, so small that can only fit six cars, one trail leads to the Gulch. The other heads to Bowling Ball Beach.
After climbing down the cliff and walking up the shore, you arrive at a flat stone platform beneath high cliffs. At low tide neat rows of huge round boulders, covered in seaweed and barnacles, sit on the playa, as though waiting for a game played by giants. At high tide they disappear beneath the surf.
The boulders are concretions, and were formed in the cliffs above when they were mud or sandstone. Inside the stone itself, while it was in the process of compaction over millions of years, a small hard item became a core around which minerals began to precipitate. Over time, the concretion grew inside the rock around it.
Twisted cliffs rise above Bowling Ball Beach. Layers of frozen stone sediment, originally the flat sea bottom, over time have been pushed up at disorienting angles. Their sharply eroded layers reach down to the shoreline, and continue on into the stone playa and the water.
Protruding from the cliffs are the strange ovoid concretions that will one day become round boulders like the others. The stone holding them into the cliff will erode away, and they will roll down onto the shore. In the ridges and arroyos of the playa protrude smaller mushroom-shaped concretions, not yet broken free as the sea’s wave action eats away their support.
The concretions on Bowling Ball Beach probably began their formation at the start of the Miocene age, in the same period when Desmostylus was munching kelp in the surf. If one molar was found by itself in nearby Schooner Gulch, is it too much to think that another molar might be hidden inside one of the concretions, the nucleus that gave it its start?
