Annularia or Asterophyllites?

[historianmichael]

A couple of years ago I visited a site in Central Pennsylvania with exposure to the Late Pennsylvanian Llewellyn Formation. I found a lot of Annularia and Calamites pieces. I also found this single whirl. I initially chalked it up as just another piece of Annularia. I recently came across the publication "Fossil Plants From the Anthracite Coal Fields of Eastern Pennsylvania." The publication has been very helpful in assisting me put a species identifications with all of my finds from the various Llewellyn Formation sites I have been to. When I tried to compare this piece to the images of Annularia in the publication they didn't quite fit. That got me thinking that it could actually be Asterophyllites equisetiformis. However, I haven't seen an example of Asterophyllites that has this pinwheel look to it- most of the examples I have seen are preserved with their leaves pointing upwards, not outwards. I have also attached an image of what I believe to be Annularia stellata that I found at the same site. You can see the clear differences between these pieces. Any help is greatly appreciated. Thanks!

 

Asterophyllites equisetiformis?

 

 

 

Annularia stellata

 

 

[Thomas.Dodson]

I'm no expert on Pennsylvanian plants but it looks like Asterophyllites equisetiformis. The specimen illustrated in Jack Wittry's The Mazon Creek Fossil Flora is rather similar and Wittry also mentions "Darrah (Darrah W. C.) said there are a large range of features seen in fossils of this taxon. Variation in leaf length, number per whorl and arching makes it likely more than one biological species has been placed under this taxon".

[historianmichael]

@Thomas.Dodson Thank you! That quote about the arching is very helpful. That feature was really the sticking point for me. I am glad to hear that there can be variation and it still be considered Asterophyllites equisetiformis.