This striking double crinoid plaque of a Jurassic sea lily, known as Seirocrinus subangularis, is approximately 180 million years old and is a huge 5ft 11in x 3ft 1in (1.8m x 95cm).
It was found at Holzmaden in Germany, a location celebrated for the preservation of its specimens. Sea lilies are among the most sought-after fossils from Holzmaden.
This example is guided at £30,000-50,000 in a sale of natural history at Summers Place Auctions in Billingshurst, West Sussex, on November 20.
summersplaceauctions.com or see this item on thesaleroom.com