My brother is somewhat of a Paleontologist. He has been studying arrowheads, indian artifacts and finding fossils, such as Nautilus, Echinoids and Ammonites. He showed me a part of his collection yesterday and I giggled in delight. Fossils Of Texas is an interesting place.
Echinoids (sea urchins) first appeared in the early Palaeozoic, and became common fossils from the Jurassic onwards, during the last 200 million years. Eupatagus, illustrated here (length 60 mm), is a genus of Cenozoic age, so locally common in sedimentary rocks (especially limestones) deposited within the very last 65 million years.
And example below found from another website.