Cycadeoidea

Cycadeoidea is an extinct genus of bennettitalean plants that lived during the Cretaceous period, and maybe even earlier in the Jurassic period. These plants were found in places like North America, Europe, and Asia. They looked a lot like modern-day cycad plants, with a short trunk and a crown of leaves on top. Scientists study these ancient plants to learn more about how the world looked a very long time ago and how plants have changed over millions of years.

Taxonomy

A scientist named William Buckland named two species, C. megalophylla and C. microphylla, in 1828 because they looked like living cycads. Two other scientists, Robert Brown and Mr. Loddiges from Loddiges Nursery, suggested this name because they had seen living cycads.

It is hard to sort the species in this group. Some scientists described trunks as different species, and fourteen more species are known only from leaves. We do not know which leaves belong to which trunks.

Description

Cycadeoidea plants had short, barrel-shaped stems with a crown of pinnate leaves on top. The trunks were covered in overlapping leaf bases, much like modern cycads. While the exact appearance of the adult leaves is unclear because trunks are often found without them, the plants had special structures for reproduction that contained both male and female parts. These structures were hidden deep in the stem under the leaves and surrounded by scales. It's possible these plants could reproduce by themselves or with help from insects. Scientists use the size and shape of the trunk to tell different species apart, but some plants look like they might be from different species simply because they are different sizes or ages.

Fossil sites and species

Scientists have found and named several types of these ancient plants. Some of the names include Cycadeoidea cylindrica, Cycadeoidea deshayesii, and Cycadeoidea duvalii.

The first examples were found on the Isle of Portland, where they were named C. megalophylla and C. microphylla. Another type, Cycadeoidea gibsoniana, was discovered in the Lower Greensand on the Isle of Wight. These fossils were very well preserved, showing details of the plant's structure.

Four well-preserved cones of C. maccafferyi were found in the Upper Cretaceous Haslam Formation in Vancouver and Hornby Island, British Columbia. Most of these plants lived during the time of the Cretaceous period, but some may have been from an even earlier time called the Jurassic.