''Euctenius'' is an extinct genus of

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

containing a single species, ''Euctenius unilateralis''. It was initially described as the tooth of the

petalodont Petalodontiformes ("thin-plate teeth") is an extinct order of marine cartilaginous fish related to modern day chimaera found in what is now the United States of America and Europe.Lund, Richard, E. D. Grogan, and M. Fath. "On the relationships of ...

genus ''

Ctenoptychius ''Ctenoptychius'' (meaning "comb-folded", from the Greek language, Greek wiktionary:cteno-, κτείς or ''kteís'' meaning "comb" and wiktionary:πτυχή#Ancient_Greek, πτυχή or ''ptychos'' meaning "fold") is an extinct genus of Chondric ...

'' or as a genus of edestid, although it more likely represents the

copulatory organ A sex organ, also known as a reproductive organ, is a part of an organism that is involved in sexual reproduction. Sex organs constitute the primary sex characteristics of an organism. Sex organs are responsible for producing and transporting ...

of an

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

. Fossils of ''Euctenius'' have been uncovered in

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

and

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

and date to the

Late Carboniferous Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * Late (The 77s album), ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudo ...

period. Identical structures are known to have been paired around the

cloaca A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...

of Opiderpetonids and were most likely used to clasp while mating. The edge of the structure is finely

serrated Serration is a saw-like appearance or a row of sharp or tooth-like projections. A serrated cutting edge has many small points of contact with the material being cut. By having less contact area than a smooth blade or other edge, the applied pr ...

, and it is covered in enamel.

References

Edestidae Pennsylvanian vertebrates of Europe Monotypic prehistoric cartilaginous fish genera {{paleo-holocephalan-stub