Changes coming for Thelypteridaceae (ferns)

A large and long-awaited update to the taxonomy of the maiden fern family, Thelypteridaceae (currently Thelypteris, Parathelypteris, Christella, Cyclosorus, Pneumatopteris, etc.) has just been published by Susan Fawcett and Alan Smith. The family represents about 10% of extant fern diversity, and Susan and Alan have divided it into 37 genera, some new, and provided extensive descriptions of each and a key to genera. Their work was published in Sida 59: you can order a hard copy or a free PDF download See this short thread by Wes Testo on why this is important for pteridology.

I feel pretty confident that this classification will be well-received, but it will entail a few changes to familiar taxa.

United States: the biggest change (in terms of observations impacted) is the transfer of New York Fern from Parathelypteris to an enlarged Amauropelta. Nevada fern goes with it; Massachusetts fern to Coryphopteris while marsh fern is unaffected. In the south, many, though not all of the large ferns treated in Thelypteris, which have been listed under Christella in Weakley’s Flora, will go to a new genus, Pelazoneuron. This will allow some more specific genus-level IDs for taxa like T. kunthii vs. T. ovata, often hard to distinguish in iNat photos.

New Zealand: relatively few thelypterids are found here, but gully fern will go from Pneumatopteris pennigera to Pakau pennigera as the former genus turned out to be a number of marginally related groups bundled together.

Several of the common tropical species will not change their names under this classification, particularly Christella dentata, C. hispidula, C. parasitica, Cyclosorus interruptus, and Macrothelypteris torresiana. In theory, impacts should be bigger in the tropics where most of the group’s diversity lies, but in practice, people rarely dare identify that diversity to species. I am hopeful that the new classification will make it easier to do at least genus-level IDs on many thelypterids.

This will take some time to roll out, and I think some of the swaps will run up against the load limits and require scheduling by staff. I think this is a good set of changes, and will improve our understanding of the family, but I wanted to put this out here to attract feedback and avoid surprises.


i vote we skip it and wait ten minutes for the next six revisions of fern taxonomy to come out. in fact i’d step new york fern back to Thelypteris.

I fully expect to be overridden here, i realize that. But especially for ferns, trying to untangle genetic phylogeny is pretty hopeless as they are backcrossed hybridized multiple ploidy levels etc etc etc. There aren’t ever going to be clear cut species and family trees so we need to just choose something that is simple and elegant and functional.


Although I haven’t studied this particular group before yet, generally it may be best to wait at least some time to confirm that it is well-received in literature, and/or contact authors of this revision and other authors in the field to learn what they think. Not that the changes “can’t” be made now, but something to at least consider, and also to check other curators’ views on this first.

Will Macrothelypteris be affected?

Not really. Circumscription of the phegopterid genera (Macrothelypteris, Phegopteris and Pseudophegopteris) is essentially unchanged; one African species has been transferred from Macrothelypteris to Pseudophegopteris (P. rammelooi).

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iNaturalist was created to connect people with nature, allow naturalists to connect with each other, and allow for a database of organisms that can be used by a broad audience of people. Constant alteration of the taxonomy iNaturalist is based on, by a few specialists and splitters, is making the site very difficult for both casual users and generalist ecologists/land managers to use, because scientific names are constantly changing making it impossible to cross reference with other guides and databases and causing broad confusion. iNat used to only allow taxonomy changes once they made their way to secondary references, and that approach worked a lot better. Somehow it has descended into mass chaos where names literally change every week, sometimes multiple times for the same taxa. There is no way this fits the goals of inaturalist.

Please return to the previous policy of only allowing taxonomy changes once they have made their way to established secondary references. Or alternatively create one nomenclature system for the splitters and taxonomic specialists where they can constantly change names and split and divide species, and also retain another nomenclature system for the rest of us who just want to collect biodiversity data using a consistent classification system.

I use iNaturalist as part of my job, to collect data. I don’t do so as much as i might, because of stuff like this.I would like to create a species list with inaturalist observations, then use a query to get that list and copy to my database. I can’t do this because the names don’t stay the same. I also use iNat to do outreach about wetlands to landowners. Again, very hard to do when the names are constantly changing. I’m honestly thinking of just going back to using common names because the common names are better than inaturalist taxonomy. That’s how bad this has gotten.

We’ve been told many times iNat is to connect people with nature, not to create a database. Under that framework this is even worse. How can you connect with nature if you can’t even identify a super common plant because its name keeps changing?

Look, i think it is neat that we have access to genetic data that affects our knowledge of evolution. While i do think people overrely on it, i also think it’s a powerful too. But, species are still a human construct. People are so obsessed with trying to avoid 'incorrect or ‘old’ taxonomy that they have completely destroyed the ability to use this site for its stated purpose. I am trying to convince landowners to stop mowing wetlands, to stop planting invasive species, to restore damaged wetlands, etc etc etc. These landowners, or at least the vast majority of them, are not plant taxonomists. Do you think they care what a polyphylletic group is? Heck, i don’t even care when it come to species names. Utility trumps correctness. Come on. I am autistic, i am plenty concerned with accuracy, so i get that. But we can’t literally destroy the site over this stuff.

So i ask, once again, PLEASE keep the taxonomy of ferns and other plants limited to at least reasonable secondary references. PLEASE. If you can’t cite something other than a recently published paper for a taxonomy change, DONT DO IT. Others use this site too. Please think of the vast majority of users. Maybe create your own parallel nomenclature where you can constantly change names but please stop doing it here.


How can you connect with nature when you can’t even identify a super common plant because some people insist that it is actually a hundred or more obscure lookalikes? [:cough: dandelion :cough:] Whether it’s one species or a hundred, it’s hard enough just to get people to want to do something other than spray it with Roundup. If they are all herbicided, you won’t have them to argue about what exact member of what exact complex they are.

well right, the dandelion microspecies thing is a good example. it should be kept at species with a ton of varieties or something. Yes some people will kill something before they understand it and yes there is far more to connecting with nature than naming things. But we are a species for whom our languages are one of our most pronounced characteristics and strengths. Words do matter. We’ve been naming plants longer than we’ve been Homo sapiens, i’ll bet. Losing the great creation of Linnean taxonomy to this sort of purity push is going to be a loss.


I have launched what I expect to be the last swaps for this process (thankfully)! Southeastern US (and some Caribbean/South American) Thelypteris s.l. is mostly now Pelazoneuron and can be identified more precisely. Existing IDs to genus Thelypteris s.l. will bump up to Thelypteridoideae to avoid conflict with the new segregate genera.

I will continue filling in and atlasing species not yet in the taxonomy, but there should be no more name changes in this family for widely observed taxa.


This amounts to a prediction that a whole new revision will be published next month.

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I feel pretty good about my predictive abilities…next big dustup will be splitting up North & Central American lady ferns, then hay-scented fern moving to Sitolobium. Maybe try to straighten out the brackens if I feel like I’m not getting enough abuse in my diet.

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I, for one, hugely appreciate the hard work you’ve put into keeping fern taxonomy up to date. It disheartens me to see how many negative reactions your efforts have received.

Yes, it can be annoying when you have to re-learn a name or something, but change is what science is all about. I hate it when things stay out of date just because someone doesn’t want to put the effort into learning a new piece of info. And if it changes again next week, who cares? Every change is a step that progresses our understanding of the organism.