Ctenacanthus

No. Ctenacanthus was an extinct Paleozoic genus of shark-like cartilaginous fish, related to sharks but not a living shark species. Fossils are known from teeth, spines and, in some cases, more complete remains. [American Museum of Natural History study](https://www.scribd.com/document/886881621/Maisey-1981)

Its dorsal fin spines often have rows of fine ridges or teeth that create a comb-like appearance. The genus name refers to this distinctive spine form, which is why isolated fin spines are often associated with Ctenacanthus. [Smithsonian Institution](https://www.si.edu/object/nmnhpaleobiology_3393028)

Ctenacanthus belongs to the Paleozoic record of early cartilaginous fishes, with members commonly discussed from the Devonian through the later Paleozoic. Exact age depends on the species and fossil formation being identified. [American Museum of Natural History study](https://www.scribd.com/document/886881621/Maisey-1981)

Many early specimens consisted only of isolated fin spines, and similar spines can occur in different shark-like groups. Teeth, braincase features and an associated skeleton provide stronger evidence than a loose spine by itself. [American Museum of Natural History study](https://www.scribd.com/document/886881621/Maisey-1981)