A gar is any of the number of fish that belong to the ancient order of fish known as Semionotiformes. Semionotiformes first distinguished themselves from related Neopterygii some 300 or 250 million years ago with a small genus of interesting fish called Obaichthys. Obaichthys was distinctive for it had a different scale arrangement from other Neopterygii. In Obaichthys the scales lacked a then common dentine layer. This was where the Lepisosteidae where born into being. Obaichthys looked much like today’s Atractosteus gars. It was an elongate fish with set back dorsal and anal fins, Caudal fin was Heterocercal, and the nose of the fish was elongate with a set of sharp needle like teeth in two rows on the upper jaw and one in the lower. Unlike modern gar however it had a movable premaxillary.
Gars (Lepisosteidae) then transitioned and evolved out into two genus in the Cretaceous 145 some million years ago. (Atractosteus and Lepisosteus). Both genus where wide spread during much of the late Mesozoic and through the catastrophic extinction that brought in the Cenozoic. Surviving members evolved some 75 MYA and have until today existed unchanged. They have elongated bodies and jaws and are clad with thick, overlapping Ganiod scales. Gars have a vascularised swim bladder that acts as a lung. This allows them to survive in poorly oxygenated waters. The flesh of Lepisosteidae is edible although the roe is toxic.
Today seven species exist only in North and Central America and on the Island of Cuba. In their glory days of the late Mesozoic, they ranged throughout North America, South America, East Asia, Africa and Europe.
Author(s): Richard Kik IV (Aquaticpredators.com)
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