See text Cyclurus (Ancient Greek for "rounded tail") is an extinct genus of freshwater amiid ray-finned fish known from the Late Cretaceous to the Early Oligocene across much of the Northern Hemisphere.

[2] Remains of Cyclurus are first known from western North America during the Maastrichtian stage of the Cretaceous with the species C. fragosus, with the genus having presumably diverged from Amia shortly before.

[1][2] Alongside Amia, Cyclurus survived the Cretaceous-Paleogene extinction event in a refugium in western North America.

The Geiseltal specimens of C. kehreri differ morphologically from the Messel ones, and may represent a distinct species.

Almost no specimens of C. kehreri are known with fish bones in their stomach (a specimen with percoid bones in its stomach is thought to have likely scavenged on them), suggesting that unlike other amiids, Cyclurus likely fed on small invertebrates instead of other fish.