Marattiopsida

Marattiopsida is a small class of ferns, containing only a single order, Marattiales, and a single family, Marattiaceae. These ferns are characterized by their large, fleshy fronds and their unique sporangia, which are fused together in synangia. Marattiopsida is considered to be a primitive group of ferns, with fossil evidence suggesting that they have been around for over 300 million years. They are found in tropical and subtropical regions around the world, often growing in moist, shady environments.

The fronds of Marattiopsida can be very large, with some species reaching lengths of over 10 meters. They are typically bipinnately compound, meaning that the fronds are divided into leaflets, which are themselves divided into smaller leaflets. The sori, which are clusters of sporangia, are located on the undersides of the fronds. In Marattiopsida, these sori are fused into characteristic synangia, giving them a distinctive appearance.

While the exact evolutionary relationships of Marattiopsida are still debated, they are generally considered to be sister to all other living ferns (monilophytes). Their unique morphology and ancient lineage make them of great interest to botanists studying plant evolution. Despite their ancient origins, the Marattiaceae are still a diverse group, with approximately 130 species described. These ferns play a role in their ecosystems as understory plants in humid forests.