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SOME VERTEBRATE FISHES FOUND IN OKLAHOMA
Acanthodii
Their tails resembled those of sharks; keep in mind this tail form is primitive to many fish groups. They are the earliest gnathostomes to appear in the fossil record, and their skin was scaled. Characteristic spines appeared on the leading edge of each fin, and their fin pattern was unique. Like many primitive fishes, they had both an anterior and a posterior dorsal fin; in addition to the pectoral and pelvic fins, acanthodians had multiple intermediate fin spines, up to six additional pairs.
Specimens of Acanthodii have been found in the Early Permian rocks of the Hennessey Formation in Tillman County. Other specimens have been found in The Boise 'd Arc Formation of Murray County (Early Devonian).
Stethacanthus
The weird "spine and brush" structure on the back of the 375 million-year-old Stethacanthus may have served as a sexual signaling device, making it easier for females to pick out potential mates, or was perhaps used in combat by males. Like many early sharks, Stethacanthus was only a few feet long.
Specimens of Stethacanthus have been found in Mississippian aged rocks of the Caney Shale in Pontotoc County.
Hybodus
The jaws of Hybodus housed two types of teeth, reflecting a varied diet. One set was sharp suitable for seizing slippery prey like fish and squid. Its other teeth were flat and strong for crushing the casings of shelled animals like molluscs and sea urchins. Judging by the size of its teeth Hybodus was about 2 metres long and almost certainly had the typical streamlined shape that all sharks have had since their first appearance in the Devonian period, over 360 million years ago.
Tillman County, Hennessey Formation, Early Permian
Tillman County, Garber Formation, Early Permian
Symmorium
Symmorium bears close similarity in size and appearance to Stethacanthus, but is missing the "spine and brush" on its back. Some scientists think that the two forms are simply the males and females of related species, while other scientists think they were different groups.
Pontotoc County, Francis Formation, Late Pennsylvanian
Xenacanthus
This fresh water shark was characterized by a large spine protruding from the back of its head as well as little forked teeth. Since it did not possess true bone, mostly spines and teeth are discovered giving a rather limited view of this interesting animal.
Tillman County, Garber Formation, Early Permian
Orthacanthus
Orthacanthus' eel-like body reached nearly 10 feet in length and its powerful jaws were lined with double-fanged teeth. Here it is about to make a meal of a small "horned" amphibian. Orthacanthus belongs to a group of very successful sharks that lived mainly in fresh waters. They first appeared almost 400 million years ago, and became extinct just before the "Age of the Dinosaurs," about 225 million years ago.
Tillman County, Garber Formation, Early Permian