Pachypteris or Thinnfeldia

[BillG]

Id'd by NHM as either Pachypteris or Thinnfeldia
Hettangian, (Lower Jurassic).
I found this in Doniford Bay, Watchet, Somerset. It actually lifts clear of the shale matrix in some places

Attachments:

[paleoflor]

Hi Bill,

There is good reason the NHM people left this open. The types of foliage belonging to the "Pachypteris-Komlopteris-Thinnfeldia complex" can only be truely kept apart from one another when the stomata can be studied. However, since the NHM people ruled out Komlopteris (or at least didn't name the option) this might be less of a problem. Pachypteris is known primarily from the Triassic and Jurassic of Europe (although accounts of Gondwana species do exist, see for example Townrow, 1965). Leaves are pinnate to bipinnate and have decurrent, blunt apexed pinnules. As you state yourself, the fossil actually lifts clear of the shale matrix at some places. This is probably cuticle-tissue. Pachypteris can be excellently preserved in that way, and can be analysed by Transmission Electron Microscopy for this reason. Komlopteris then, is a segregate of Pachypteris. The main difference is the positioning of the stomata, something which cannot be determined easily by amateurs (however, I suppose the people from the NHM did this for you, or they should have mentioned this option). Historically (and to my liking, since I posted a Dicroidium leaf here just some days ago) the genus Thinnfeldia was used for Dicroidium-like leaves that did not come from Gondwana. The holotype (Jurassic of Romania) for the type species (T. rhomboidalis) was later shown to be a Pachypteris (Dolukdenko, 1971; Doludenko et al., 1998). Therefore, today Thinnfeldia is often taken to be a synonym of Pachypteris (see for example Popa, 2000). However, there still is some dispute about this (e.g. Kirchner and Muller, 1992) since some of the leaves of both groups are associated with different types of reproductive organs. In short, I do not think it will be easy to do a better job than the people at the NHM did, unfortunately...

B.T.W. This information and much more on the subject can also be found in: Taylor T.N., E.L. Taylor and M. Krings (2009), Paleobotany; the biology and evolution of fossil plants [2nd ed.], Academic Press

[paleoflor]

Oh, in al the turmoil of trying to make my story clear I forgot to mention: fantastic specimen!

[BillG]

Thanks Joe, when it was sent back to me, the guy who id'd it said it would be a good specimen for further analysis. Although he didn't ask for it, (in 2007), I intend to donate it, if he wants it. I have filed his letter away somewhere and will look it out, and tell you what he said, and who he was.

[paleoflor]

Well, like I said: it is possible to do cuticle-analysis on this specimen. So I reckon this person at the NHM will be interested, yes. And if not, you could contact our paleobotany department here at Utrecht University. I know some people who surely would like to get a closer look at your Pachypteris/Thinnfeldia specimen...

Best regards,

Tim

[BillG]

Sorry Tim, I called you Joe in my last. I have a few specimens of it so Utrecht Uni are welcome to a bit.
Here's a close-up of a loose piece.

Attachments:

[paleoflor]

I'll show this post to prof.dr. Han van Konijnenburg-van Cittert. She is an expert on the Jurassic of Yorkshire, and Mesozoic floras in general and might be interested.

(If you have ample of material, I myself (although no professional in the field) would also be interested in a trade or something; very interesting material!)

Cheers,

Tim