Cycadeoidea

Cycadeoidea

Cycadeoidea is an extinct genus of bennettitalean plants from the Cretaceous period, and perhaps even earlier in the Jurassic period. These plants were discovered in North America, Europe, and Asia. They looked very similar to modern-day cycad plants, having a short trunk and a crown of leaves on top. Scientists study these ancient plants to understand the past world 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, similar to modern cycads. While we do not know exactly what the adult leaves looked like because trunks are often found without them, the plants had special structures for reproduction. These structures had both male and female parts and were hidden deep in the stem under the leaves and surrounded by scales. Scientists use the size and shape of the trunk to tell different species apart.

Fossil sites and species

Scientists have found and named many types of these ancient plants. Some of the names are 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 well preserved and showed 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 Cretaceous period, but some may have been from the Jurassic period.