Dinner for Insects

Cedrelospermum lineatum

Cedrelospermum is an extinct plant belonging in the elm family (Ulmaceae). It is one of the two most common fossil plants found at Florissant and is a good example to show traces of insect feeding on plants as well as how plants can be reconstructed using multiple organs such as leaves and fruits. Cedrelospermum was probably an abundant tree around the margin of the lake, and its small wind-dispersed fruits suggest that it was an early successional plant that could have colonized the landscape after a volcanic eruption.

This reconstruction of a fruiting branchlet of Cedrelospermum lineatum shows the attachment of leaves and winged fruits. The serrated leaves are alternate on the branch and the secondary veins have distinct branches that lead into the sinuses (notches) between the teeth. The winged fruits are sheathed by a cup-like calyx around the base and have one large primary wing and a much smaller secondary wing.

Fossils of Cedrelospermum leaves were once thought to belong with the living genus Zelkova, which is native to Europe and Asia, while the isolated fossils of winged fruits were first identified as belonging in the family Proteaceae, which now grows in only the southern hemisphere. The mystery of Cedrelospermum’s true identify was revealed by paleobotanist Dr. Steven Manchester in 1989 after he examined a fossil specimen in a museum that had been collected more than a century earlier by the Princeton Scientific Expedition to Florissant in 1877. Looking closely at this fossil, he found that the leaves and fruits were connected, showing that they were actually part of the same plant! Using this knowledge, we are now able to reconstruct what a branch of this tree would have looked like. It’s possible that some of the fossil wood from Florissant also belongs to this tree, but since we can’t prove that it’s attached to the foliage, we may never know for sure.

The fossil evidence shows that Cedrelospermum probably first evolved in North America during the Eocene and later dispersed to Europe and Asia, becoming extinct during the Miocene. The shared distribution across these continents is evidence for ancient connections across the North Atlantic land bridge with Europe and the Bering land bridge with Asia.