You raise a valid concern. I know what you mean. You're thinking of ones like this
But the lines on Calamites lines can be the sort of width we see in Vince's specimen (about 3mm);
here are some examples
- http://pedagogie.ac-montpellier.fr/svt/litho/graissessac/exploitation%20peda.htm (3rd on the left)
And you can see both narrow and broad types in this single photo
Also, Sigillaria can have striped bark, but there are usually still leaflet scars visible in it, as in these examples
Calamites does not have leaflet scars spread over the surface like Sigillaria; similar scars are concentrated in whorls - rings spaced-out along the stem. Where the Calamites fossil is an internal (pith) cast, there will be no scars but the whorl lines will still be present.
Also, Sigillaria does not have the whorls around the stem that Calamites does.
In Vince's specimen, we can see no leaflet scars, and we can see part of a whorl.
On the subject of petrified wood and similar material, this is relevant
- a page on Calamites, including a pith cast
The rest of that site is interesting, too - if you're into this sort of thing. I think the section 'The Anatomy of Arborescent Plant Life Through Time' is especially good. It includes many fine examples of the cellular structure I often ask folks about on NaturePlus to look for when they're wanting to know 'is this fossil wood' (or bone, or something else).
Thanks for the hints, tips, prompts and suggestions you've provided to this and other related posts. You've provided a wealth of info and I'm going to try to go through it asap. From what I've looked at I'm wondering if the images I provided are clear enough. This particular rock seems to have an additional layer running through it and there is a small section where the face of underlying layer is exposed and the same pattern is visible. It looks as if there are two leaf sections - 1 visible on the surface and the other approx 5mm below. I'm inclined more and more to think it's a fern leaf - either that or a massively flattened stem. I did find a similar image on a web page but didn't say what it was...
Nothing wrong with questioning our suggestion; everybody can have their own opinion.
Personally, despite my original reply, I am sure it is Calamites. The flatness is not a problem: here's an example of a flattened one. The presence of multiple plant fossils on different- or the same surface is not unsual: here's an example (not Calamites), and another; and your own image. The presence of the whorl-line is pretty distinctive for Calamites/relatives.
Have you looked in the same area for more fossils? There will probably be loads of fossils in your area from the Carboniferous period. Where I find all of my plant fossils, fragments of them litter the ground, and it's very enjoyable collecting them.
Here are some of the fossils which I have found in West Yorkshire
Hi again Vince. Here are some other fossils which I have found.
1. Calamites root
2. Trigonocarpus seed (very hard to find, especially in the summer when not as much erosion takes place.
3. A fossil branch/ trunk section, which I think could be the species Neuropteris.
If you keep looking, you'll probably find similar fossils. After 1 year of collecting, my biggest fossil branch is 8.5", and my biggest fragment of wood is the size of a large boulder (so it was too big to take home.)