Pecopterid Fern: Polymorphopteris Vs. Lobatopteris

[AHoffman]

So I'm back again with more plant fossil questions, but this time I am hopefully a little less clueless. I got Jack Wittry's guide to Mazon Creek Flora and have been trying to learn as much as possible. I am interested in comparing what I have found so far to an earlier study by Roger Boneham (http://journals.iupui.edu/index.php/ias/article/download/8143/8102) on the Pennsylvanian fossil flora and fauna of the Chieftain Mine site (now Fowler Park, Vigo County, IN) but I am running in to some nomenclature issues that make it difficult to decipher which fossils were found in the study. I am also having trouble differentiating some fern species with very similar venation (at least to my untrained eye). Jack was kind enough to clear up some of my questions about general identification and taxonomy in a previous post and he stated that based on what venation he could see and the form of the pinnules, the fern in question appeared to be Acitheca (Polymorphopteris) polymorpha. I have spent a good few hours since then going over numerous ferns with a magnifying glass and a bright light and have been able to see the veins on many of the specimens relatively clearly. Since I think my photographs obscure the venation even further, I have posted photos and sketches based on what I can see below:

- 4.5 X 2.25cm (the nodule) Sketch -

- 6 X 4.5cm (nodule)

- 5.5 X 3.25cm

- Sketch showing more clearly the transition in shape of the pinnules closer to the base

- 8 X 4cm

I have also found a negative of what appears to be the same type of fern that is ~11cm long and similar in form to the first picture. So I guess my question is, are all of these Polymorphopteris, are they something different, or are they a mix of species? So far, all of the ferns I have found with visible venation (~20) appear to be the same thing to me (similar venation, size, and form) so I suspect this has to be one of, if not, the most common species at this site. Boneham notes Asterotheca miltoni as "one of the most common species" and I suspect this is what I am finding. The only problem, is that it seems this species has been sunk (or at least reassigned) and in his book, Jack notes that both Polymorphopteris and Lobatopteris have been previously called Asterotheca/Pecopteris miltoni. For those interested, so far Cyperites preservations are the second most abundant fossil I've found with Macroneuropteris and Annularia stellata following next in line respectively. I apologize if I have asked too many questions at once or if my ignorance is showing in any all too obvious ways haha...I am still learning and it is a steep learning curve! I really appreciate all of the help you all have given me so far and I look forward to hearing your comments.

-Andrew

[Rockaholic]

Wish I could help you with your quest for knowledge but my level of understanding of Pennsylvanian fossil flora and fauna is still in its infancy. Thanks for the link.

[AHoffman]

No Problem, I might add (as I'm not sure I made it clear), my fossils also came from that site (Chieftain Mine) which is why I am interested in making that comparison.

[paleoflor]

Don't know if you have access to it, but the paper by Zodrow et al. (2006) may shed some light on your questions, at least to the point of getting more insight into the different genera (the 'historical burden' makes this rather complicated, to me at least).

Zodrow et al. (2006) Taxonomic revision of the Palaeozoic marattialean fern Acitheca Schimper

Abstract: The Pennsylvanian genus Acitheca Schimper, 1879 is revised based on re-examination of the sterile types, plus evidence from well-preserved fertile and sterile material from Canada and the Czech Republic (n=750 specimens). Acitheca was an arborescent marattialean fern about 3.5m high with large, tripinnate or quadripinnate fronds which produced Caulopteris-like frond scars on the trunk. Although its reproductive structures are similar to those of Asterotheca Presl, Acitheca differs in a number of characters of the sterile foliage (especially the venation), and its palynology. The veins fork at least twice (except in the smallest pinnules): after the first dichotomy, the upper branch divides and then the lower branch divides, producing polymorphopterid veining pattern. Synangia occur in two rows, one on either side of the midvein, and usually consist of four elongate sporangia that extend beyond the pinnule margin. Recovered in situ spores show a much greater ontogenetic variability than any other known Pennsylvanian marattialean; the size varies from 34μm to 116μm, and exine ornamentation from laevigate (immature spores), finely microgranulate to scabrate (intermediate spores), to microverrucate–microgranulate (mature spores). Three species are described in the paper: Acitheca polymorpha (Brongniart) Schimper, Acitheca ambigua (Sternberg) Němejc, and a new species Acitheca alii sp. nov. Distributional evidence suggests that Acitheca probably originated in eastern North America and Western Europe in middle Pennsylvanian, and towards the end of it its geographical range had extended to Eastern Europe, the Caucasus, and into Permian of China.

In addition, the paper by Pšenička et al. (2009) is an interesting, and on-topic paper:

Pšenička et al. (2009) Description of synangia and spores of the holotype of the Carboniferous fern Lobatopteris miltoni, with taxonomic comments

Abstract: Pinnules of the holotype of Filicites miltoni Artis (Duckmantian–early Moscovian, Middle Pennsylvanian age) have two rows of synangia, one on each side of the midvein. Each synangium is borne on a short receptacle and consists of three or four claviform sporangia that are separated from each other along most of their length. The sporangia contain trilete spores with a microverrucate to microgranulate exine. F. miltoni appears to be congeneric with the syntypes of Pecopteris vestita Lesquereux, which is the type species of the morphogenus Lobatopteris Wagner.

EDIT - I do not (yet) have a copy of the paper by Wagner (1958), in which the name Lobatopteris is coined. However, I requested the material in our library. I'll do my best to scan the interesting bits for you.

Edited September 27, 2013 by paleoflor

[AHoffman]

Thanks for that information and the links! Unfortunately I do not have access to those two pubs (past the abstract and figures of course). Any chance you could send me the PDFs? My email is hoffmana10<AT>alumni.hanover.edu.

[fiddlehead]

As one of the et. al's or authors of the Psenicka (2009) paper on Lobatopteris miltonii I would like to add information to the abstract given and a small peak into the widow of convoluted taxonomy for this species. Pecopteris (Filisites) miltonii Artis is con specific to Pecopteris vestita Lesquereux, but not con specific to Lobatopteris (Pecopteris) vestita sensu Wagner. The two "vestita's" are different species. Wagner used an incorrect interpretation of Lesquereux's vestita. He thought P. vestita Lesquereux was the very common fern of Middle Pennsylvanian age, found throughout Europe and North America. Most notably its from Mazon Creek where I mistakenly published (2006) it as Lobatopteris lamuriana and is the most common true fern. It is also common in the Radstockian of England. Lesquereux was describing a fern from older strata of Lower Pennsylvanian age from Missouri. His form was discovered to be synonymous to Pecopteris miltonii Artis making P. vestita a junior synonym of it since miltonii (it should be two i's since it turns out to be erected from a person's name not a place) was erected first. If you are not confused enough, one more thing, Wagner says miltonii is not a lobatopterid in effect saying his type species for his genus is not a member of the genus. Big problem. A paper should hopefully be out this year which will correctly establish a new binomial name for what has been called Lobatopteris vestita sensu Wagner for the last several years.

The bottom picture is an example of Lobatopteris vestita sensu Wagner or more correctly (for now) Pecopteris acadica Bell, 1962. The species name acadica is correct regardless. You drew the classic lobatopterid venation. Mature ultimate pinnae of P. acadica have a defining characteristic of ten lobes per side which can't quite be seen in this example. Visit the Smithsonian's web site for better examples. http://paleobiology.si.edu/mazoncreek/mazonFilicopsida.html

Good luck,

Jack

[AHoffman]

Thanks Jack,

You have enlightened me as to the complexities and taxonomic upheavals still underway in this field. I feel silly for grumbling over having to learn a couple new genera names for the North American Ranid frogs and Bufonid toads a few years back. So based on your comments, it seems likely that Pecopteris acadica is a common species around here then. Are there any other lobatopterids that would display similar venation (making identification impossible in immature/incomplete specimens)? Also, I have heard the term "pecopterid" thrown around a number of times and now you use the term "lobatopterid". These of course sound like family level designations but are they actual plant families or are they groups that fall into a similar category based on form (with little to no idea of their true taxonomic placement)? I hope to find some larger/more complete specimens that will fall into place a little better but as of yet most of the plants I find are small/immature (but still quite beautiful). I've enjoyed looking through your book and your comments have been a big help!

-Andrew

[Plantguy]

Hi Andrew, I'm glad Jack was able to comment on your questions and share his expertise again. I've been asking lots of questions too and trying to understand as well without the years of study/training/research--I cant begin to keep up with it. Seems describing fragmentary plant remains independently from world wide locales over the years has created an exceptional mountain of literature/collections to sort thru to compare/clarify. These folks really have their work cut out for them.

I'm content nowadays to have someone figure out the genus most of the time with a well preserved specimen. .

Thanks Jack for sharing the insight! Regards, Chris

[AHoffman]

Hi Chris, the more I read and hear the more I realize how difficult it must be to study taxonomy of extinct plants based on fragmentary remains scattered across sites that compose different parts of different plants. I sure am gaining a respect for the people that do it and I agree, in most cases I think genus would be great (although to me it seems that even the generas are complicated and tough to get too haha). I suppose that is the incentive for me to get out and find better specimens!

[paleoflor]

As one of the et. al's or authors of the Psenicka (2009) paper on Lobatopteris miltonii I would like to add information to the abstract given and a small peak into the widow of convoluted taxonomy for this species. Pecopteris (Filisites) miltonii Artis is con specific to Pecopteris vestita Lesquereux, but not con specific to Lobatopteris (Pecopteris) vestita sensu Wagner. The two "vestita's" are different species. Wagner used an incorrect interpretation of Lesquereux's vestita. He thought P. vestita Lesquereux was the very common fern of Middle Pennsylvanian age, found throughout Europe and North America. Most notably its from Mazon Creek where I mistakenly published (2006) it as Lobatopteris lamuriana and is the most common true fern. It is also common in the Radstockian of England. Lesquereux was describing a fern from older strata of Lower Pennsylvanian age from Missouri. His form was discovered to be synonymous to Pecopteris miltonii Artis making P. vestita a junior synonym of it since miltonii (it should be two i's since it turns out to be erected from a person's name not a place) was erected first. If you are not confused enough, one more thing, Wagner says miltonii is not a lobatopterid in effect saying his type species for his genus is not a member of the genus. Big problem. A paper should hopefully be out this year which will correctly establish a new binomial name for what has been called Lobatopteris vestita sensu Wagner for the last several years.

The bottom picture is an example of Lobatopteris vestita sensu Wagner or more correctly (for now) Pecopteris acadica Bell, 1962. The species name acadica is correct regardless. You drew the classic lobatopterid venation. Mature ultimate pinnae of P. acadica have a defining characteristic of ten lobes per side which can't quite be seen in this example. Visit the Smithsonian's web site for better examples. http://paleobiology.si.edu/mazoncreek/mazonFilicopsida.html

Good luck,

Jack

Perhaps a stupid what-if question, but what if Wagner had not changed his 1958a diagnosis (and included species list) in the 1971 paper (in which he apparently reassigned L. miltonii (Artis) Wagner 1958a to Pecopteris) - how would this change the picture regarding the current status of Lobatopteris? Nomenclatural changes are always confusing.

Another question I now have is, is whether the "lobatopteroid venation" concept is still valid (basically Fig.6 in Wagner 1958b and your Fig. 2)? Lobatopteris is defined as a formgenus in Wagner, 1958a, but it is also related to Corsin's Miltoniae (2009 paper mentions Asterotheca auct synangia - though not in the 1958a diagnosis). How does that work exactly?

Thanks for your input, I am learning a lot more this way than by just reading the papers!

[fiddlehead]

There are a lot of ways Lobatopteris could have been erected better. You have to have a type species that represents all the features you are applying to the new genus and in this case it had none of them, including fertile structures. Wagner did not included fertile features in his original diagnoses of Lobatopteris, which was allowed in 1958. This is very important character and a fact that would have to be included to be even considered to have any hope to pass a peer review. As to the last question, both Pecopteris acadica=Lobatopteris vestita sense Wagner and Lobatopteris miltonii have the very common compression synangia form Asterotheca as do most species of Marattialean ferns. The problem is the spore types are different. As shown in the Psenicka (2009) paper; miltonii has trilete spores, and P. acadica (Asterotheca sp. 4 Pfefferkorn et. al., 1971) has monolete spores (upcoming paper). Monolete spores are a feature that all "lobatopterids" share along with lobatopterid vein development. Clearly major nomenclature changes regarding Lobatopteris must be addressed. I prefer to leave the majority of this very complicated issue for the upcoming paper to explain.

The simple answer to the "what if" question is if Wagner would have used a correct name for the form he intended; the common "lobatopteried" fern from Mazon Creek (personal communication) there would be very little to discuss. A sharp reader will note that P. acadica was not erected till 1962; four years after Lobatopteris. In 1958 it would have been necessary for Wagner to name a new species. This form had no correct name, a fact missed by every paleobotanist for over a 150 years. Today's P. acadica has been called, villousa by Lesquereux and White; miltonii by Kidston, Janssen and Bell; vestita by Noe, Cleal and Wagner; lamuriana by Darrah, Gastaldo, and Wittry. We all had it wrong. All the names apply to demonstrably different forms. We did not do are homework. Only Bell realized a mistake was being made, which even he had made at one time. He corrected the situation by erecting a new name, though this paper was missed by most till recently. The fact that one of the most common and important index fossil ferns in the Middle Pennsylvanian had no correct name is a testimony to the fact that natural science still has lots to be learned even in a discipline as old as paleobotany.

Hope this makes sense. Stay tuned.

Jack

[paleoflor]

Thanks for the detailed and clarifying answer. Given the arguments you provide (e.g. spore types), it will probably be difficult to apply these new devlopments in nomenclature for pectopteroid foliage (at least, for an amateur like me - unless there is a "kitchen utensil-based approach" palynological analysis, ha-ha). Nevertheless, I am much looking forward to reading the upcoming paper!