Hippuritidae

an extinct family of bivalve mollusks of the order Rudistae. They have been found in Upper Cretaceous beds. The valves of the shell differed sharply. The right valve was bottle-shaped and up to 1 m tall; the left was slightly convex or concave. Hippuritidae inhabited the seas. They led a stationary way of life and held fast to the soil with the right valve.