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Excerpts from Jim Conrad's
Naturalist Newsletter
Notes from an April 1, 2019 camping trip in Seibal Archaeological Park about 15kms east of Sayaxché, Petén department; tropical rainforest, elevation ~220m (~720 ft), ~N16.492°, W90.209°
SERPOCAULON DISSIMILE
Along a shadowy forest trail between ruins a fern turned up looking a little different from others I'd seen. It's shown below:
At first I thought it was one of the swordferns, genus Nephrolepis, especially because of the shape of the pinna bases, somewhat eared, as shown below:
But then I turned the blade over and saw what's shown below:
Nephrolepis pinnae bear two rows of round, spore-producing sori, not four rows. In fact, I'd never seen any fern species so neatly equipped with four rows of round sori. This was something new for me, and exciting.
It turned out that one reason I had a hard time identifying this species is that until 2006 the species was assigned to a very large fern genus (up to 250 species), Polypodium, which was not well understood, and the literature on its tropical members was rather sparse. Our Guatemalan species now has been shifted to a newly formed genus, Serpocaulon, the most visible difference between it and its former Polypodium compainons being its species' long-creeping, scaly rhizomes, its distinctive blade venation, its sori in one to ten rows, and its species being entirely tropical or subtropical in the Americas, while most Polypodium species are north-temperate, Mexican or Central American.
Our Guatemalan fern is SERPOCAULON DISSIMILE, distributed from southern Mexico and the Caribbean south through Central America into northwestern South America. It has no good English name. Most pictures I find of it show it growing on trees as an epiphyte, though ours seemed to be on the ground.
So far not much information has been gathered on the species. It's just one of those taxa contributing to the gorgeous diversity of life.