Cheirolepis

Cheirolepis trailli

• Europe, Canada

Cheirolepis is a bony fish from the Middle Devonian. The first fossil remains of this species were found in the Old Red Sandstone in Scotland, more fossils are from Canada. Cheirolepis is the first well- known ray-finned fishes and probably the primitive sister group of all other known ray-finned fishes. Former members of the class have been handed down only from the late Silurian in the form of individual scales.

Features

Cheirolepis was about 25 inches long. His body was lean and was covered in small, rhombic, overlapping scales. The scales were held in curved diagonal rows obliquely backward and downward. They were made of bone, dentin, and a melt- like substance on the outside ( Ganoidschuppen ). The caudal fin was clearly heterocercal, but the lower caudal lobe was enlarged. The upper edge of the tail was amplified by enlarged keel scales. Dorsal and anal fins were large and triangular.

The skull was large and heavy, braincase and palate were ossified. The skull was covered in thin Dermalknochen. The large eye sockets sit near the front. The mouth was filled with large and irregularly distributed sharp teeth. The jaw edges are formed by the maxilla and premaxillary bone ( premaxilla ) in the maxilla and dentary in the lower jaw bone, which are the main tooth-bearing bones also in all subsequent vertebrates. The trailing edge of the skull is connected to the gill area and the shoulder belt. Since the skull was strong movable jaw could be opened very wide.

Way of life

Cheirolepis was a predator who could swim fast and was probably oriented at catching prey with their eyes. The large, highly mobile jaw allowed him to devour prey, which reached 2/3 of their own body length. In the stomach region of Cheirolepis remains of barbed sharks ( Acanthodii ) and the lung fish Dipterus were found. Maybe they ate too little Placodermi they not bite with their sharp teeth, palate with blunt teeth but could possibly crush.