Description
Silicified Sponge
Cretaceous
Garraf, Catalonia, Can Casanyas Castellet, Spain
53mm silicified sponge.
Paleontologists consider sponges to be among the oldest groups of modern animals. It appears that they diverged from their ancestors in Precambrian time because Cambrian-age sponges already bear the same biomineralized skeletal structure as modern forms. How that skeleton evolved from a more simple form and what that simple form was remain a mystery.