GoFossilHunting

Paleogene · 66.0 – 23.03 Ma

Paleogene fossil sites

Mammals diversified explosively after the dinosaurs vanished. The earliest whales and primates appeared in the Paleogene. Sites like the London Clay (UK), Florissant (Colorado), and Fur Formation (Denmark) preserve exceptional Paleogene biotas.

The Cretaceous–Paleogene boundary in Colorado, a dark coal seam banded between pale sandstones
Photo: Jeffrey Beall, CC BY 4.0, via Wikimedia Commons

The Paleogene opens immediately after the extinction that ended the Cretaceous. Mammals and birds expanded into the space the dinosaurs left behind. The early part of the period was hot. Palms grew in Wyoming and crocodiles lived above the Arctic Circle. Climate then cooled through the Eocene and Oligocene toward the modern pattern.

Paleogene deposits preserve unusually fine detail. The London Clay yields fruits, seeds, and crab carapaces. The Fur Formation of Denmark preserves insects and fish between volcanic ash layers. Green River lake beds in Wyoming split into slabs holding complete fish. Shark teeth are common in marine Paleogene sand on both sides of the Atlantic.

Forty-six entries here sit in Paleogene rock, and twenty-two allow free collecting. Seven sit in the United Kingdom and six in Denmark, where the moler cliffs of Fur and Mors are the best known exposures. Washington State supplies five more, including the Chuckanut plant beds.

46 fossil sites

Updated 4 August 2026

Life of the period

Three to know from the Paleogene

You will not find all of these yourself. They are the animals and plants that make the period worth reading about.

  • A life-size sculpture of a giant snake coiled outdoors on wood chippings.
    Giant snakeTitanoboa

    Around 13 metres long, from Paleocene coal beds in Colombia. Snakes cannot generate their own heat, so a snake that size implies a much warmer tropics than exists today.

    Mojmir Churavy, CC BY-SA 4.0

  • The long toothed skull of an early whale mounted against a green wall.
    Ancient whaleBasilosaurus

    The name means king lizard, given before anyone realised it was a whale. It kept small hind legs, far too small to walk on, left over from ancestors that lived on land.

    Ninjatacoshell, CC BY-SA 3.0

  • A fossil fish preserved whole on a pale slab of lake sediment.
    Green River fishKnightia

    Wyoming's state fossil and probably the most collected fossil fish in the world. Mass death layers in the old lake beds preserve whole shoals on a single slab.

    NPS photo, Public domain

All Paleogene sites

Frequently asked questions

What can I find in the London Clay?
Shark and ray teeth, crab carapaces, fossil wood riddled by shipworm, and pyritized fruits and seeds. The Isle of Sheppey and the Essex coast are the classic collecting grounds. Pyrite specimens need dry storage or they decay.
What is moler?
Moler is a Danish diatomite, a soft rock made of microscopic algal skeletons and interleaved with dark volcanic ash bands. It formed about 55 million years ago and preserves insects, fish, and birds in fine detail. Fur and Mors expose it.
Where can I find Eocene shark teeth?
In marine Eocene sands on both Atlantic coasts. The Aquia Formation of Maryland and Virginia is productive in the United States. Bracklesham Bay and the Isle of Sheppey are the standard British sites.