When I briefly considered the many different ways I might someday become a fossil, I tried to hit many of the most common interment scenarios. There’s burial at sea, beneath a sand dune, along a floodplain, and various other places where sediment accumulates fast enough to protect a body for the long haul. But there was one specific case that I neglected to mention. Entombment in poop is also an option.

We know that inhumation in guano is a pretty good way to make a fossil because of a spectacular sloth. You can go see it yourself at Yale’s Peabody Museum of Natural History. Wave hi to the museum’s Brontosaurus as you walk past, shuffle by the pack of Deinonychus, and turn right into a place where far too few museum visitors tread – the The Fossil Mammal Hall. There, behind the glass next to the snarling Smilodon, are the remains of a Shasta ground sloth, tatters of skin and fur still clinging to the bones.

Had the sloth been any less spectacular, Yale geologist Chester Longwell might not have endeavored to claim it. This was a hard-won skeleton. Led to the spot in the New Mexico desert by Ewing Waterhouse, who had alerted Yale to the discovery in the winter of 1928, Longwell was brought to a yawning fumarole made by an extinct volcano. The body of the sloth lay on a steep slope in the darkness some one hundred feet beneath the mouth of the pit. The only way in was a rope climb down the steep walls of the cave.

Paleontologist Richard Swann Lull, who later wrote the official report on the skeleton, left out the details of Longwell’s exertions. But all that hard work yielded the finest Shasta ground sloth ever seen. This species had been found before, most notably at California’s La Brea asphalt seeps, but the sloth skeletons from the black mire were composites made of multiple animals. Yale’s new sloth, on the other hand, was undoubtedly a single individual, so tightly bound by its own preserved ligaments that Lull had trouble articulating the body into exactly the position he wanted for display in the Peabody’s mammal hall.

Lull’s restoration of the Aden Crater sloth, with the end of the tail restored and the hands turned. Credit: Lull 1929

Only a few pieces of the sloth’s skeleton were missing. Some of the ribs had corroded on one side, possibly because moisture accumulated on the flank the sloth rested on, and there were a few miscellaneous bones that had been lost, but otherwise everything was held tightly in place. And even though much of the skin had apparently been gnawed off by rodents, patches of skin and the claw sheaths remained intact. In fact, the environment was so amenable to preservation that one of the sloth’s dung balls was preserved with the beast. Analyzed by botanist Arthur Eams, the coprolite was packed with sagebrush twigs and roots. Apparently the sloth pulled up whole plants by the roots and chewed through the entire, bristly meal.

But it was dung of a different sort that protected the sloth’s body from degradation for the 11,000 years that it lay in the pit. Over time the sloth’s body was coated by dried bat guano, shielding it from scavengers, and the warm, arid New Mexico climate prevented the skeleton from rotting. That’s something to consider for anyone who might wish to leave their remains to the ever-growing fossil record. Burial in batplop might not be the most dignified, but you can’t argue with the results.


Lull, R. 1929. A Remarkable Ground Sloth. New Haven: Yale University Press.

[This post was originally published at National Geographic.]