Life image of Gyrodus hexagonus. Fossils of this pflasterzähnigen Gyrodontiden found in the Upper Jurassic Solnhofen Solnhofen
The Pycnodontiformes are an extinct order of bony fishes ( Osteichthyes ). They lived on the Upper Triassic to the Eocene. So far, about 650 species have been scientifically described in 37 genera.
The Pycnodontiformes had a hochrückige shape. Dorsal and anal fins are extended fringe-like; the caudal fin is homocerk. For advanced Pycnodontiformes only the front body is scaly. Their muzzle is slightly extended and set with pin-like teeth. They probably fed on hard-shelled invertebrates such as clams, snails, echinoderms and crustaceans. All Pycnodontiformes up on the benthic pelagic Coccodus lived.
Way of life
The Pycnodontiformes were mainly inhabitants of reefs and lagoons on the edge of the Tethys. After the opening of the Atlantic in the Jurassic they also inhabited the newly formed sea. Fossils of Pycnodontiformes were found among other things in the Italian fossil deposit Monte Bolca and in Solnhofen in Bavaria.
Fossil record and evolution
The Pycnodontiformes are mainly in the fossil record in the form of scales, bones and teeth, some genera have been described solely on the basis of teeth. Based on such evidence can the evolutionary history of this group of fishes follow over a period of 175 million years ago. Your fossil record extends from the Upper Triassic ( Norian ) of the northern margins of the Tethys (now in northern Italy and Austria ) until the Eocene. Their heyday with a rapid development of new types lies in Jurassic and Cretaceous. In the Mesozoic and Paleogene they are an important part of fossil fish Socialization world.
Recent studies show that the Pycnodontiformes are the sister group of the genuine bony fish ( Teleostei ).