Fossil bear claw marks in the cave wall at Oregon Caves National Monument. NPS photo.
A cave is a trap and a vault at once. Sediment and bones wash or fall in and stay; the temperature and humidity barely change for thousands of years; and so caves keep fossils that would have weathered away anywhere in the open. The National Park Service has documented cave fossils in at least 56 parks, from ice-age condor nests in the Grand Canyon to fossil birds in the lava tubes of Haleakalā.
Two kinds of cave fossil
Cave fossils turn up in two settings:
- in the rock the cave formed in — older fossils exposed on the walls, like a nautiloid in a rock shelter on the Buffalo National River in Arkansas;
- left by animals and plants of the Pleistocene and Holocene — creatures that lived in the cave, wandered in, or were washed in after death.
Either way they fall into four groups: fossil plants, invertebrates, vertebrates, and trace fossils — marks left by an animal rather than the animal itself, like bear claw marks on a cave wall.
Where to find them
| Region | Parks and what they hold |
|---|---|
| Grand Canyon and Glen Canyon | one of the largest concentrations of caves in the country; ice-age condors and their nests; Rampart Cave, where saber-tooth cats, ground sloths and a bat are preserved in layers of sloth dung; farther up the Colorado, a site with mammoth dung instead |
| South-central New Mexico and west Texas | Carlsbad Caverns and Guadalupe Mountains: rich Pleistocene vertebrate fossils, mostly mammals |
| East and Midwest | Mammoth Cave (Kentucky), Cumberland Cave on the Potomac Heritage Trail (Maryland), Port Kennedy Cave at Valley Forge (Pennsylvania), caves along the Buffalo National River (Arkansas) — some recording rare middle Pleistocene faunas |
| Black Hills and the Rockies | Jewel Cave and Wind Cave (South Dakota); remote caves in Yellowstone |
| Cascades and Hawaiʻi | Oregon Caves, where bears clawed the walls; Lava Beds; Haleakalā's lava caves, with fossil birds |
Figure 5: Fossil nautiloid exposed in a rock shelter along the river at Buffalo National River, Arkansas. NPS Photo.
Ground sloth dung from the Pleistocene, preserved in Rampart Cave at Grand Canyon. NPS photo.
Why the dung matters
Rampart Cave's fossils are unusual because of what surrounds them. Layer after layer of ground sloth dung records what the animals ate and when, and the bones in it place saber-tooth cats and bats in the same ice-age canyon. The mammoth-dung site upstream does the same for a different giant. Caves hold not just skeletons but the everyday traces of how extinct animals lived.
Look, do not take
Both caves and their fossils are fragile and cannot be replaced. A visitor who finds a fossil should leave it where it is and tell a ranger. In October 2018 the Park Service opened an exhibit on its cave fossils, with a map of every park that has them, at the National Cave and Karst Research Institute in Carlsbad, New Mexico.
Figure 1: New exhibit panel for the NPS Cave Paleontology exhibit to open in October 2018 at the National Cave and Karst Research Institute. NPS photo.
Sources
Written from Vincent Santucci, "National Park Service Cave Paleontology", Park Paleontology newsletter (Fall 2018), NPS Geologic Resources Division, a work of the United States government in the public domain. Pictures an earlier version of this page left out were restored on 2026-09-26.
Licence: CC0 1.0 (public domain) · Adapted from www.nps.gov
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