So just what the hell is a Gar?
And just why is it important to distinguish a Lepisosteid from other fish that may share their common name?
First lets tackle “What is a Gar?”
In our use, we are calling a gar 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.
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.
Gar morphology:
Lepisosteids have unique morphology that is quite different from the later evolving and less advanced Teleosts species that have come to take over the earth. As mentioned an important trait is that the scales are unlike other Actinopterygii fishes (Living examples being Polypterids and Sturgeon) and other Neopterygian Fish (Bowfin). Gar scales have a cosmine lower layer that has a dense ganoin layer on top but it lacks the Dentine layer found in previous fish. Other traits are the presence of a spiral valve at the end of the intestine, Vascularized air bladder (that is essentially a “lung”
, heterocercal tail, and opisthocoelous (concave posteriorly and convex anteriorly) vertebra.
OK…. That is a gar by definition for the most part..
A definition of Lepisosteidae and what it is that defines them...
Later we define Not gars... provide examples and discuss just why it is important to distinguish them..
And just why is it important to distinguish a Lepisosteid from other fish that may share their common name?
First lets tackle “What is a Gar?”
In our use, we are calling a gar 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.
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.
Gar morphology:
Lepisosteids have unique morphology that is quite different from the later evolving and less advanced Teleosts species that have come to take over the earth. As mentioned an important trait is that the scales are unlike other Actinopterygii fishes (Living examples being Polypterids and Sturgeon) and other Neopterygian Fish (Bowfin). Gar scales have a cosmine lower layer that has a dense ganoin layer on top but it lacks the Dentine layer found in previous fish. Other traits are the presence of a spiral valve at the end of the intestine, Vascularized air bladder (that is essentially a “lung”
, heterocercal tail, and opisthocoelous (concave posteriorly and convex anteriorly) vertebra.OK…. That is a gar by definition for the most part..
A definition of Lepisosteidae and what it is that defines them...
Later we define Not gars... provide examples and discuss just why it is important to distinguish them..
