Helodus

Not to be confused with Henodus.

Helodus (from Greek: ἧλος helos, 'stud' and Greek: ὀδούς odoús 'tooth')^[1] is an extinct genus of cartilaginous fish from the Upper Devonian through Lower Permian.^[2] While the type species, H. simplex from the Late Carboniferous (Moscovian ~ 315 million years ago)^[3] of England is known from articulated specimens, the rest of the species in this genus are known only from isolated teeth.^[4] Over twenty species have been attributed to this genus, many of which may be anterior teeth of other cartilaginous fish. This makes Helodus a wastebasket taxon.^[5] Only the type species can be confidently attributed to this genus until articulated remains of other species are found.^[4] H. simplex was around 30 centimeters (1 foot) long,^[2] and males had a large, tooth-bearing clasping organ on their heads. The teeth of H. simplex, which were arranged in tooth-whorls, were transitional between elasmobranch-like separated teeth and the tooth plates of living chimaeras.^[3]

Helodus Temporal range: Moscovian PreꞒ Ꞓ O S D C P T J K Pg N
Tooth file of Helodus simplex
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Holocephali
Order:	†Helodontiformes
Family:	†Helodontidae
Genus:	†Helodus Agassiz, 1838
Type species
Helodus simplex Agassiz, 1838