Giant teeth and whale tales.

• Author: Harrington, Gail

IF THERE'S ANYTHING Roberto Penny Cabrera enjoys more than finding prehistoric shark teeth in the Ocucaje Desert, twelve miles inland from the Peru's southern coast, it's witnessing one of his expedition clients discover a fossilized tooth of the Carcharodon megalodon, one of the the ocean's largest predators, which lived two million to sixteen million years ago. "First, I look for a spot with powdery rust-colored soil, the organic remains of plankton, in which case I'll often find fossils, shells, small pieces of bone, and also shark teeth," Cabrera says. "But there must be a very strong wind hitting the ground at an angle that erodes the sediment and uncovers the shark's teeth."

A retired military officer, former prospector for mining companies, and self-taught expert on geology, Cabrera impresses even paleontologists with his observations and intuitive reasoning that help him identify the places most likely to reveal recently uncovered shark teeth. And anyone who's ventured a hundred miles off road into the Ocucaje with Cabrera in his powerful 1981 Datsun diesel truck soon learns not to waste time searching unless he's inspected an area and given it a thumbs-up. "Roberto understands stratigraphy--the layers, distribution, and age of sedimentary rock--and erosion so well, he knows exactly where to find those shark teeth," says paleontologist Ingo Meyer, former head of excavation at the University of Hamburg.

A stunning mix of tiered escarpments, sedimentary rock, level stretches, sandy valleys, and pre-Cambrian volcanic mountains, the Ocucaje is one of the quietest and driest places on earth, a desert without living creatures, measurable rainfall, or anything that has a scent. Other than an isolated clump or two of blackened dried-out plants that somehow manage to sprout bright orange flowers even without water, the only signs of life are millions of years old, not just fossilized shark teeth but also intact whale skeletons that include the fossilized spine, vertebrae, skull, eye sockets, and even the brains.

"Part of the Pisco formation, this whole area was once at the bottom of a large shallow bay, mostly open to the ocean," says Leonard Brand, a professor of paleontology at California's Loma Linda University...