Because it could be a crime scene?

With any bone that's possibly human-sized, the first thing I do is call a specialist in human osteology. I can get in as much trouble as anybody else on the job site for messing around with human remains.

QAThat's the thing most people don't get. The first question is, “Is this a homicide?” Or they can be Native American (bones), and then there's a whole protocol to deal with that.

QYou monitored the Calaveras dam seismic retrofit, which lasted from 2011 to 2018, for the San Francisco Public

Yeah. We worked with the construction firm and used their heavy equipment. We're talking about whales, so in a couple of cases, we're removing things that probably weighed two or three tons. I have now seen more 15 million-year-old dead whales than I've seen modern dead whales. Those remains went to the University of California Museum of Paleontology.

How about the Transbay Transit Center?

With that one, a dredge operator picked up a big clamshell bucket of wet sediments, dropped it down on the ground and from 30 feet away, saw a

There was a horse there, probably from the Ice Age. Horses were pretty common — we see them along the 680 corridor and have found them on the South Peninsula. They ran in big herds. You'd be hard pressed to tell them apart from a modern horse; they were slightly smaller on average.

What's one of the most unique fossils you've found?

At one project we worked on, for a public utility in Alameda County (around 2015 to 2017), we found a marine vertebrate called a desmostylus. It looked kind of like a small hippopotamus, but is probably more closely related to elephants. It has the dubious honor of being the only order of marine mammal to have gone extinct.

It's interesting, because we're quite concerned now about dugongs (a manatee cousin) and animals like that. These are animals sitting on the edge of extinction. In some ways, desmostylus kind of filled a similar niche — it was an herbivore, like dugongs are today. So understanding them helps us understand what's going on today.

QDo you ever just dig up junk? Old batteries, car hubcaps and the like?

AI often get people contacting me with what turn out to be rocks. Probably one of the hardest things for me to do is let them down gently. Because it's kind of a bummer: They're really excited, they think they found something, but it's often just a rock. But I'm a geologist, so there is no such thing as “just a rock.” I tell them all about their rock, and it keeps them interested in it.