Spying on Whales. Nick Pyenson

back to whales, as a scientist, has always involved skulls in one way or another. In college I puzzled over a half-rotten dolphin head when our field class, on a barrier island off the coast of Georgia, discovered its carcass buried in the sand. The putrid smell dispersed the rest of the class, but I held fast. I wasn’t riveted by the grotesque allure; instead I was captivated for the first time by the thought of how, exactly, a whale might become a fossil.

      In graduate school, I sought fossil whale skulls peeking out of seaside cliffs or crumbling out of rock formations in badlands that were once seafloors. Cetaceans became my vehicles for understanding life over geologic time, across scales so vast that we cannot truly comprehend them, even if paleontologists casually discuss geologic markers as if referring to last week’s dentist appointment. And it all led me to the Smithsonian, where I tend to the world’s great collection of fossil whale skulls.

      However, part of the deal with being a museum scientist, especially at the Smithsonian, is that people ask you for tours. It’s more than a fair trade. First, I like giving tours. They give me an excuse to try out new ways to talk about ideas—the big ones, like the evidence for evolution and extinction—that not only excite me but also explain how whales came to be. Also, tours often involve children, and children are usually the toughest audiences of all, whether they’re whale huggers or fossil fiends. If I can figure out how to keep them interested, even for a short show-and-tell, then I think I’ve done my job. And who knows, I might even be convincing enough to ignite more than a passing interest.

      My friend and colleague Megan McKenna first taught me about whale heads and their inner biosonar anatomy when we were both in graduate school, so when she brought her family recently for an early-morning tour before the museum opened, I was excited at the opportunity to settle a debt. Her four-year-old daughter was just a bit older than mine. The museum’s halls, especially when they’re empty, can be intimidating spaces, so I started slowly—I didn’t want to overwhelm or manufacture too much excitement.

      As we walked into the Sant Ocean Hall, we stopped short underneath the imposing right whale model, and turned to face the eel-like skeleton of Basilosaurus, grimacing from above. Basilosaurus is an early whale several million years younger than Pakicetus and Maiacetus but it looks worlds apart in size and shape. Its dinosaur-sounding name literally translates from Latin as “king lizard,” in a nod to its serpentine, bus-length body. The first fossils of Basilosaurus were collected from the chalky marls of rural Arkansas and Alabama in the early nineteenth century. With a skull over three feet long, jaws bearing palm-sized, saw-shaped teeth, and individual vertebrae large enough to serve as stools, a Basilosaurus skeleton gives every impression of belonging to a sea monster—and its name has stuck, if only for the conventions that scientists use to name species.

      Unlike today’s whales, Basilosaurus has a head that does not dominate its body, arms that crook at the elbows, and a surprising, diminutive set of legs that could never have supported its large weight on land. But Basilosaurus has an involucrum like all the other early land-dwelling whales, and its ear bones floated in a sinus space below its skull. Basilosaurus did not echolocate, nor filter feed, leaving it caught somewhat in an evolutionary middle ground for whale evolution: one of the first fully aquatic whales, completely unreliant on land, yet still carrying many of the biological apparatuses of its terrestrial ancestors.

      A Basilosaurus tooth

      As I walked with Megan under the skeleton, I pointed to its hind limbs and joked aloud about how they dangled like poorly placed, miniature landing gear. Megan then leaned down to her daughter. “Hey, Etta, Nick studies whale bones just like those ones.” Etta looked at me intently, mulling the assertion. “Why?”

      I opened my mouth to deliver a canned response involving school, science, and curiosity, more boilerplate than authentic. I knew I could do better. I waited a few beats.

      “Their bones all tell stories,” I said, “about where whales came from.” She glanced up at Basilosaurus looming from the ceiling, like a giant, flippered, macabre snake. “And if you become a scientist, you can learn to read them and know their stories.” I knew I had her attention. “But they sure don’t just show up here in the museum all put together,” I smiled. “You have to find them first.”

      

      I walked with my eyes trained on a long, gray road cut through a hillside on a cattle ranch. In the late-afternoon California sun, the waving golden grass gave the hill the look of an enormous, shaggy animal, revealing its sedimentary flank. I followed a small path, parallel to the exposed fossil-rich layer. Walk, stare, walk some more, scrape the exposure, and then walk again; maybe you get lucky.

      A few yards away from me, my colleague Jim Parham was doing the exact same thing. I’ve known Jim since graduate school, and we don’t need to say much to each other in the field. Jim’s an expert on turtles and other reptiles. As it is for me with whale bones, Jim has seen enough specimens that even the smallest fragments of fossil shell can help him solve riddles about turtle origins, which stretch back even deeper in geologic time than whales, though we tend to find fossil sea turtles in the same type of rock as fossil whales. Jim and I reliably fall on the same page, by temperament and by rock units.

      We had visited many other outcrops in the foothills of the Sierra Nevada together. We worked side by side, scanning in silence. “Hey,” Jim said abruptly, reaching down. He raised a palm-sized shark tooth to the sky, its serrated edges cutting the orange light. I looked down and immediately started to see other shark teeth and whale bone fragments recently eroded out of the hillside, gems in the rough. “Oh, check this out,” I said, retrieving a segment of dolphin rib from the newly formed sediment piles. As I flipped it over between my fingers, I noticed something unusual—a set of a dozen parallel lines gouging a path across the bone’s surface. A shark bite. This site was, after all, the Sharktooth Hill bonebed.

      The fact that the rib bone belonged to a small species of extinct toothed whale (Odontoceti indeterminate, if you want to be technical) was probably the least interesting thing about it. That kind of identification is merely born out of the same patient study—hours with museum collections—that gives you eyes for spotting bones in the first place. Far more interesting was the fact that it told us part of a story: a little more than fifteen million years ago, in the middle of the Miocene, an ancient shark chomped down on an extinct dolphin’s rib cage.

      Whether this particular set of bones represented a fatal encounter or mere scavenging on a carcass we couldn’t know. There was also no real way of knowing whether the shark tooth in Jim’s hand and the marked rib in mine were causally related. We held the two side by side, checking the serrations on the tooth with the gouges on the rib—close, but not a precise match. Even if they were, it would be a stretch to tie the two pieces of evidence, a gumshoe’s leap in causality at a suspected murder scene. Whale bones do tell us stories, but they’re not always satisfying or predictable.

      I lodge finds like these on the shelves of whale bones that I keep in my head. I can’t quite tell you how this mental library is organized, but I slip into it every time I see a shard or glint of whale bone, whether out in the field or in a museum drawer. The more fragmentary, the more fun. I pick it up carefully, thumb its creases, divots, and twists, and then scrutinize its topography by eye. My thoughts immediately race through a chain of mental flash cards to arrive at the best possible identification of its former owner: Right or left side? Symmetrical, from the main axis of the skeleton? Cranial or something below the neck? Scavenging marks? Pathologies? These flash cards are marked with names for every bump and hole on a bone’s surface. It has taken me years to build up this cerebral collection, long hours spent with many skeletons within arm’s reach, flipping each piece over and over again, tracing each surface for memory. It’s also good to keep a stack of real literature on hand as a guide,