Leptosporangiate fern

Leptosporangiate ferns are a big group of plants that love shady, moist places like forests. They are one of the four main kinds of ferns and make up the largest group, with about 11,000 different species found all around the world. These ferns get their name from special structures called sporangia, which grow from a single skin cell. When these sporangia grow up, they have thin walls and often have a little cover called an indusium to protect them.

Unlike some other ferns, leptosporangiate ferns have a special ring-like part called an annulus that helps shoot their tiny seeds, known as spores, into the air. Many of these ferns grow on other plants, like trees, instead of the ground — these are called epiphytes. Together with the eusporangiate ferns, horsetails, and whisk ferns, they make up all the living ferns we see today.

Taxonomy

Leptosporangiate ferns were first identified as a group in 1881 by Karl Ritter von Goebel. Later, in 1884–9, Christian Luerssen separated these ferns into two groups. The group we now call leptosporangiate ferns has been classified in different ways over time.

In 2006, scientists used molecular studies to better understand how these ferns are related. They included water ferns within this group and raised it to a class called Polypodiopsida. More recent classifications, like those from 2014 and 2016, group all fern subclasses together under Polypodiophyta.

Subdivision

Today, leptosporangiate ferns are divided into seven orders, 44 families, 300 genera, and about 10,323 species.

Phylogenetic relationships

Recent studies help us understand how leptosporangiate ferns relate to other plant groups. It now seems that Equisetopsida is most closely related to Psilotopsida.

Discussion of molecular classification

Some people have questioned recent studies that use molecules to understand how ferns are related. They say these studies might not give a full picture because they don’t include information from ancient ferns found as fossils. But, these molecular studies have helped us learn more about the families of ferns that were already thought to be mixed groups. Even though we didn’t have enough information before, these studies give us the best understanding we have today. This is because looking at the shape and features of ferns alone doesn’t always show how they are truly connected in nature.

Extinct families

Leptosporangiate ferns have many fossils that scientists have studied. Some of these fossils, like those from the Dicksoniaceae family, date back to the Lower Jurassic period, about 201 to 175 million years ago. Several other families that no longer exist have been described, but they do not fit into the way we classify living ferns today.

Some of these extinct families include Anachoropteridaceae, Botryopteridaceae, Kaplanopteridaceae, Psalixochlaenaceae, Sermayaceae, Skaaripteridaceae, Tedeleaceae, and Tempskyaceae.