Acer eonegundo facts for kids

Acer eonegundo is an extinct type of maple tree. This means it's a species that no longer exists today. Scientists know about it from just one part of a fossil leaf. This special fossil was found in Eocene rocks in Nevada, USA. Acer eonegundo belongs to a group of living maple trees called the Negundo section.

Discovery and Classification

The only fossil of A. eonegundo ever found came from northeastern Nevada. It was discovered in an area known as the "Bull Run" flora. This area has ancient lake sediments mixed with ash from volcanoes. These volcanoes erupted on and off between 43 and 38 million years ago.

Scientists used a method called radiometric dating on volcanic ash layers. This showed the plants in the "Bull Run" flora lived around 41 million years ago. Other plant fossils from the same time were found in places like Copper Basin and Elko.

The main fossil used to describe A. eonegundo is called the holotype. It is kept at the University of California Museum of Paleontology in Berkeley, California. Two paleobotanists (scientists who study ancient plants) named Jack A. Wolfe and Toshimasa Tanai studied this fossil. They officially described A. eonegundo in 1987.

The name eonegundo has a special meaning. "Eo" comes from "Eocene," which is the time period when the plant lived. "Negundo" refers to the Acer section Negundo, the group of maples it belongs to. So, its name means "an Eocene member of the Negundo section."

A. eonegundo was one of six Acer species that Wolfe and Tanai described from the "Bull Run" flora in 1987. Some of these species, like A. taurocursum, were only known from their fruits. Others, like A. axelrodi, were known from both leaves and fruits. A. eonegundo is special because it was the oldest leaf fossil found for the A. sect. Negundo at that time.

What the Leaf Looked Like

The fossil leaf of A. eonegundo was a compound leaf. This means it was made up of at least three smaller leaf parts called leaflets. These leaflets had veins arranged like a feather, which is called pinnately veined. Each leaflet could be up to 4.8 centimeters (about 1.9 inches) long.

The leaflets had small stems called petiolules. Their bases were not symmetrical; one side flared out more than the other. Each side leaflet had seven main veins that branched near the edge. One branch curved up to join the next vein, while the other went to the leaf's edge. These outer branches supported the spaces between the teeth on the leaf's edge.

The teeth on the leaflets were also compound. This means each large tooth had one or two smaller teeth on its lower side. The leaf also had smaller veins, called tertiary veins, that formed a pattern of sharp and right angles. These veins were spaced about 0.7 to 1.3 centimeters (0.28 to 0.51 inches) apart. Even smaller veins, called quaternary veins, formed a network of irregular shapes, like tiny polygons.