Dinner for Insects

Fossil fruit of Cedrelospermum. (FLFO 11740A)

NPS

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.

 

Artist reconstruction of a fruiting branch. (Based on the following fossil specimens: FLFO 2636A, FLFO 2584A, FLFO 11740A, FLFO 2805AB, FLFO 11696, FLFO 57, FLFO 67)

NPS/SIP Mariah Slovacek

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.

 

Artist reconstruction of a Cedrelospermum tree.

NPS/SIP: Mariah Slovacek

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.

 

Fossilized Feast

Left image
Fossil leaf with a skeletonized portion in the center from an unknown insect. (FLFO 2796B)
Credit: NPS

Right image
Artist reconstruction of damaged leaf.
Credit: NPS/SIP Mariah Slovacek

Some of the fossil leaves from Florissant show damage that was caused by feeding insects. Leaf beetles are among the culprits that feed on modern elm leaves, leaving “skeletonized” leaf veins as traces of their activity, similar to what you see in this fossil leaf. The study of fossil leaf damage helps us understand the coevolution of plants and insects and provides evidence for this interaction during times of changing climate. 

 

References and Acknowledgements

Manchester, S.R., 1989, Attached Reproductive and Vegetative Remains of the Extinct American- European Genus Cedrelospermum (Ulmaceae) from the Early Tertiary of Utah and Colorado: American Journal of Botany, Vol. 76, No. 2, pp. 256-276. 

Manchester, S.R., 1987, Extinct Ulmaceous Fruits from the Tertiary of Europe and Western North America: Review of Palaeobotony and Palynology, Vol. 52, pp. 119-129.

Special thanks to Dr. Steven Manchester, Florida Museum of Natural History