Vertebraria indica

The root system of a Glossopteris tree, segmented lengthways into chambers so that in cross-section it looks like a string of vertebrae — hence the name.

Those chambers were air spaces. They allowed oxygen to reach roots growing in waterlogged, poorly drained swamp soils, in the same way that mangroves and other wetland plants aerate their roots today.

Vertebraria is a form genus: it is the name given to the roots alone, because they are usually found detached from any leaves and cannot be matched to a particular species of Glossopteris.