I found these in Devonian strata (Lower? Old Red Sandstone) Feshwater East, Pembrokeshire. I believe them to be Pachytheca but I can't find much info on this type of fossil and the explanations I have found seem to contradict each other. Can anyone give me the up to date thinking on this one?
Also, most sources state that it is an independent vegetable organism, yet the layer in which the spheres are contained seems to have a semi-continuous blobby film of organic matter (I assume it's organic as it's mostly the same colour as the spheres, grey/black).
The hand specimen was just a loose bit of the outcrop, the layer of these fossils stretched for at least a metre
Here is what the Fossil plant expert had to say about your specimens:
"These small fossils are most probably Pachytheca, which are quite common in certain Late Silurian and Early Devonian fluvial sediments. If you break one open, you should see two distinct concentric zones inside: an outer one of minute radiating tubes and an inner circular (spherical) one of minute intertwined tubes. In this setting, the fabric of the fossils is predominantly coalified, but frequently they also contain microcrystalline pyrite infilling.
Although the internal structure of Pachytheca has been well-characterised, its function and its affinities are not well understood. Plant, algal, and fungal affinities have been suggested. Science is still looking for a definitive explanation of Pachytheca."
So still mysterious, but very interesting.
Your observations on Pachytheca support my suspicion that it is part of a less compact organism. I would like to mention this in connection with another brief contribution on Pachytheca at www.chertnews.de . If you agree, please contact me.