Leptecodon

Leptecodon (meaning "small tooth") is a genus of prehistoric mackerel-like ray-finned fish which was described by Williston in 1899 and was possibly preyed on by other sea creatures. However, it was a hunter of smaller creatures itself. This fish sometimes hid in clams such as Inoceramus. The first-discovered fossil was inside a clam. Many believe that Leptecodon had formed a symbiotic relationship with the clam rather than get eaten by Inoceramus. Another fish from the same time and place, Caproberyx, has also been found among Inoceramus.