Helodus
| Helodus Temporal range:
| |
|---|---|
| |
| 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
| |
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]
References
[edit]- ^ Roberts, George (1839). An etymological and explanatory dictionary of the terms and language of geology. London: Longman, Orme, Brown, Green, & Longmans. p. 76. Retrieved 30 December 2021.
- ^ a b Arno Hermann Müller: Textbook of paleozoology. Volume III, Vertebrates, Part 1. Gustav Fischer Verlag, 1985.
- ^ a b Cohen, Karly E.; Coates, Michael I.; Fraser, Gareth J. (2025). "Teeth outside the jaw: Evolution and development of the toothed head clasper in chimaeras". Proceedings of the National Academy of Sciences. 122 (37). doi:10.1073/pnas.2508054122.
- ^ a b Itano, W.M., Lambert, L.L. A new cochliodont anterior tooth plate from the Mississippian of Alabama (USA) having implications for the origin of tooth plates from tooth files. Zoological Lett 4, 12 (2018). doi:10.1186/s40851-018-0097-8
- ^ "Extinct - complete list | Species | Shark-References". shark-references.com. Retrieved 2020-11-29.
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