The gladius of giant squid are sometimes found in mudstone near Richmond. The gladius is a flat structure the thickness of cardboard that runs along the body of the squid to stiffen it as it swims backwards through the water.
One of the largest fossilised squid possibly ever found in the world is on display at Kronosaurus Korner, the Boreopeltis soniae. The gladii are composed of chitin (similar to our fingernails), which is normally devoured by scavengers and bacteria within weeks of depostion on the sea floor so are rarely fossilised. However, given over-salty, calm sea water, with summer temperatures, it can be phosphated within days and develop into fossils.
The squid in Australia’s ancient inland sea reached almost 2m in length. They were probably a favourite prey item for marine reptiles such as Kronosaurus and ichthyosaurs.