Fossil sponges

During a work party at the nature reserve yesterday, I picked up a couple of fossil sponges and have just been adding them to my collection. Here you see just a few of the sponges I've picked up from various flint piles and excavations in the chalk, including spoil heaps outside badger setts. They were formed during the Cretaceous period, around 100-80 million years ago, by flint nodules forming around different species of sponges that had died on the sea floor and been preserved in the soft chalk sediment. The largest specimen here, cracked open to reveal fine detail of the sponge body, is around 11 cm across; the smaller ones just 2.5 cm across.