An ancient fish, presumably Calamopleurus, fossil from the Triassic Period. Circa 252 to 201 million years ago. Calamopleurus is a prehistoric genus of marine halecomorph ray-finned fish from the Early Cretaceous of South America and northern Africa. It was a relative of the modern bowfin, with both belonging to the family Amiidae. Paleontological Finds For Collectors.