Luccio alligatore (Atractosteus atrox)

Alligator pike (Atractosteus atrox) Footprint, about 45 million years old, U.S.A. Fossil 96x55x3.2 cm Provenance: market (Italy) Conservation status. Surface area: 95%. Conservation status. Support: 90% (consolidation, small gaps) A truly inimitable fishing trophy? The specimen up for auction is a pike from about 45 million years ago, scientifically classified as atractosteus atrox(until recently known as lepisosteus atroxa following Leidy's 1873 cataloguing), a genus of pike in the family Lepisosteidae, an ancient group of ray-finned fishes that inhabited the fresh, brackish and occasionally marine waters of eastern North America, Central America and Cuba in the Caribbean. They are the only surviving members of the Ginglymodi, a clade of fishes that first appeared during the Triassic, more than 240 million years ago, and are one of only two surviving groups of Holostean fishes, along with the bowfins, which have a similar distribution. Our specimen does not differ much from modern alligator pike, which have elongated bodies heavily armored with ganoid scales and fronted by similarly elongated jaws filled with long, sharp teeth. Unusually for a fish, their vascularized swim bladders can function as lungs, and most pike emerge periodically for air. Incidentally, although a freshwater fish, pike have the ability to survive in high-salinity waters with little oxygen after swallowing air. It usually prefers brackish and shallow waters with slow movement, usually living in schools. Its diamond-shaped armored scales each consist of a double layer of bone. The outer layer is super dense and so hard that even large alligators have difficulty biting through it. The inner layer is more spongy and attached to a sheet of connective tissue that acts as a shock absorber. All scales are joined together with male-female joints, which allow the fish to twist and flex. The fossil in the auction-whose robust scales and sharp teeth are clearly visible-was excavated in the Green River Formation, near Lincoln, Wyoming. The Green River Formation (Green River Formation) is an Eocene (56 to 33.9 million years ago) geologic formation that records sedimentation in a group of intermountain lakes in three basins located in the United States along today's Green River in Colorado, Wyoming and Utah. The sediments are deposited in very thin layers, a dark layer during the growing season and an inorganic light-colored layer in the dry season. Each pair of layers is named varva and represents a year. The sediments of the Green River Formation show a continuous record of six million years. The average thickness of a varva here is 0.18 mm, with a minimum thickness of 0.014 mm and a maximum of 9.8 mm. Notably in Lincoln County, west of Gosiute Lake, Wyoming, lies a part of the formation known as Fossil Lake because of the abundance of exceptionally well-preserved fossil fish.