Clypeaster echinoderms can get very large and this specimen fits the bill. It's from the Miocene of Italy and was sent to me by my friend, Gery. It's dimensions are 5 inches long, 4.5 inches wide and 2.5 inches tall.
Normally these echinoderms, also called "Sea Biscuits", can be found crawling on the sandy bottom or sometimes burrowing into it. They typically have a fine coating of small spines that they use to walk on. They are extant (still found alive today) in Caribbean shallows among kelp beds.
Want to see how one of these fossils is prepped and preserved? Click here to go to You Tube for a great video.