Name: Florissant Formation
Location: USA
Age: Eocene/ Oligocene (33-34 Mya)
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3. Fauna and Flora

1683 species of organism have been found in the formation so far. These include over 140 species of tree and other plants, leaves are common and are normally found as impressions. The site is also famous for its petrified forests, massive Giant Redwood stumps have been found, the largest of which is 12 feet tall and 35 feet in circumference.

Florissant is also famous for its vast numbers of insect fossils. So far over 1100 different species have been found. Over half the species of fossil butterfly that have ever been found in the world were discovered at Florissant.

Preserved leaf from Florissant

Thousands of specimens have been taken from the fossil beds since they were discovered in 1873. These are now distributed around the world in many museums. Early scientists involved in collecting from the site were Samuel Scudder, T. Cockerell and H. McGintie. Scudder collected over 25,000 fossil insects in his lifetime. 60,000 specimens have been collected in total, covering a wide range of taxa including many insects and plats, birds, fish and mammals. The mammals included marsupials and ancestral horses. A full list of all species discovered at the site can be found on the National Parks Service website.

Populus crassa (Pemberton, 1992) is remarkable because it is one of the few specimens discovered that shows evidence of the evolution of mutualism between insects and plants. This species shows clear evidence of possessing nectaries outside the flower that may have evolved for arthropod-plant interaction.

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