Lepidodendron sp.

The trunk of a scale tree, a giant relative of today's clubmosses. The diamond-shaped pattern covering the surface is not bark texture but a dense array of leaf cushions — the scars left where long, grass-like leaves attached directly to the trunk and fell away as the tree grew.

Lepidodendron reached more than thirty metres, but was not built like a modern tree: the trunk was mostly soft tissue with a thin woody strand, supported instead by a thick outer rind. The plant grew as an unbranched pole for most of its life, branched once into a crown, reproduced, and died.

Scale trees were the principal coal-formers of the northern Carboniferous swamps.