Glossopteris is the largest and best-known genus of the extinct order of seed ferns known as Glossopteridales. Glossopteris was a dominant plant throughout the Permian and much of the Illawarra Coal Measures are made up from the deciduous leaves that the plant dropped in the cooler seasons. They disappeared in almost all places at the end of the Permian. This example is of part of the root system and is know as vertebraria, similar in appearance to a backbone which is why it was given this name. Specimen from the Illawarra of NSW.

http://en.wikipedia.org/wiki/Glossopteris