Anecdotal evidence suggests that an alligator gar can grow up to 10 ft (3.0 m) in length. Their common name was derived from their resemblance to the American alligator, particularly their broad snouts and long, sharp teeth. Gars are often referred to as " primitive fishes" or " living fossils" because they have retained some morphological characteristics of their early ancestors, such as a spiral valve intestine, which is also common to the digestive system of sharks, and the ability to breathe in both air and water. The fossil record traces its group's existence back to the Early Cretaceous over 100 million years ago. It is the largest species in the gar family (Lepisosteidae), and is among the largest freshwater fish in North America. The alligator gar ( Atractosteus spatula) is an euryhaline ray-finned fish in the clade Ginglymodi of the infraclass Holostei / h oʊ ˈ l ɒ s t i aɪ/, being most closely related to the bowfins. Atractosteus adamantinus ( Rafinesque 1818).