See text Cylindracanthus is an extinct, enigmatic genus of marine ray-finned fish with fossils known throughout North America, Europe, Asia and Africa from the Late Cretaceous to the late Eocene[1], with potential Oligocene records and a possible Miocene record also known.

[2][3][1] It is exclusively known from its distinctive partial remains, which are long cylindrical bony spines that are usually considered rostrum fragments, as well as some associated teeth.

These spines are abundant & widespread throughout this timespan, and are useful indicators of a nearshore marine environment, but the taxonomic identity of the fish is still highly uncertain and debated.

[3] However, later studies have found to be the structure of the rostrum to be dissimilar, and it is thus unlikely to be closely related.

Later, some later studies suggested closer affinities to the Acipenseriformes, based on the potential for the spines to be the only bony parts of an otherwise cartilaginous ray-finned fish akin to chondrosteans.