Hancock Mammal Quarry

Within the depths of the Clarno strata is a 40 million year old point bar, formed by the buildup of silt, sand, clay, and gravel traveling around the bend of an ancient stream. The seasonal flooding of Clarno’s semitropical forest washed away an incredible variety of dead animals and plants to the point bar, preserving a record of a diverse forest, rich with a variety of both plants and animals. Dozens of strange-looking animals are fossilized in the Hancock Mammal Quarry including Haplohippus – small 3-toed, leaf-eating horses; large rhino-like animals called brontotheres; and Acheanodon – bear-like animals similar to modern pigs. The large scavenger Hemipsaladon feasted on the carcasses, while cat-like animals hunted prey here.

Hancock Mammal Quarry mural depicting strangely similar animals walking in a drying river bend with a volcano in the background and lush, tropical forests hugging the river bend.
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Mural by Roger Witter

Hancock Mammal Quarry outline of the mural with dominant fossil labeled number one through ten. It is an outline drawing of animals walking in a drying river bend with a volcano in the background.
Key to mural
Dominant fossils found in this assemblage:
  1. Brontothere (rhino relative)
  2. Protapirus hancocki (tapir)
  3. Eubrontotherium clarnoensis (large brontothere)
  4. Diplobunops (agriochoerid animal)
  5. Epihippus gracilis (three-toed horse)
  6. Zaisanamynodon protheroi ("marsh rhino")
  7. Teletaceras radinskyi (ancestral rhinoceros)
  8. Haplohippus texanus (three-toed horse, more primitive than Epihippus)
  9. Hemipsalodon grandis (carnivore the size of a bear)
  10. unidentified vines

Charismatic Fossils

Eubrontotherium clarnoensis was a brontothere, a type of perssiodactyl (odd toed ungulate). Although it resembles a rhino it is more closely related to horses. It had two knob-shaped horns that pointed straight up. This large brontothere would have spent its time browsing on twigs and leaves, lumbering about the forest floor.

Hemipsalodon grandis was a large terrestrial carnivore that might have fed on slower herbivore mammals like Plesiocolopirus hancocki and Teletaceras radinskyi. It only lived in North America but had smaller Hyaenodontidae relatives that lived in warmer climates further south.

Epihippus gracilis was an odd toed ungulate (hooved animal) that is believed to have evolved from Orohippus, which continued the evolutionary trend of efficient grinding teeth. E. gracilis had three toes that gave it the edge of maneuverability as the environment at the time was thickly forested. Another horse lived alongside E. gracilis named Haplohippus texanus, which had more primitive characteristics.

For a complete lists of fossils found at the Hancock Mammal Quarry, email us.


Last updated: September 9, 2022

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32651 Highway 19
Kimberly, OR 97848


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