a.k.a. the 'Anvil Shark' and 'Ironing Board Shark'

Name: Stethacanthus (Chest spine).
Phonetic: Stef-ah-can-thus.
Named By: John Strong Newberry - 1889.
Classification: Chordata, Chondrichthyes, Elasmobranchii, Symmoriida, Stethacanthidae.
Species: S. altonensis, S. concavus, S. productus, S. praecursor, S. mirabilis, S. resistens, S. thomasi.
Type: Carnivore.
Size: Approximately 70 centimetres long.
Known locations: China, Europe, North America and Russia.
Time period: Late Devonian.
Fossil representation: Many specimens making Stethacanthus one of the best represented of early shark.

       As a prehistoric shark, Stethacanthus immediately stands out from its modern day brethren. Unlike the triangular dorsal fin that people associate with sharks today, The dorsal fin on Stethacanthus was shaped like an anvil. In addition to the unusual shape, small spikes covered the growth as well as appearing on top of the head. These spikes were larger versions of the placoid scales that cover the entire bodies of sharks and work by reducing drag and allowing sharks to swim more efficiently. It is still unknown what benefit the large spikes provided, but with its distinctive dorsal fin, Stethacanthus would have had no problem recognising others of its own species. Further, it seems that only the males had this 'brush' of spikes. Two long cartilaginous tendrils also trailed from the back of pectoral fins, but there exact purpose is also unknown.
       It is thought that Stethacanthus dwelled in coastal waters feeding upon fish and cephalopods much like modern sharks do today. Large quantities of Stethacanthus teeth concentrated in some locations has led to speculation that Stethacanthus may have migrated to breeding grounds during the course of its life.
       In 1982 another specimen of Stethacanthus dubbed the 'Bearsden Shark was discovered in Scotland near Glasgow. This was a very important find as much of the cartilaginous skeleton was preserved. Such an occurrence is extremely rare and this makes the Bearsdon shark fossil one of the best preserved shark fossils in the world.

Further reading
- Carboniferous fishes from the central western States - Bulletin of the Museum of Comparative Zoology 39:163-226 - C. R. Eastman - 1903.
- Two new Stethacanthid sharks (Stethacanthidae, Symmoriida) from the Pennsylvanian of Indiana, USA - Palaeontographica Abteilung A 213:115-141 - R. Zangerl - 1990.
- Early Carboniferous Fishes (Acanthodian, Actinopterygians, and Chondrichthyes) from the East Sector of North Qilian Mountain, China - Vertebrata PalAsiatica 42(2):89-110 - N. Wang, J. Fan & W. Wang - 2004.
- Symmoriiform sharks from the Pennsylvanian of Nebraska. - Acta Geologica Polonica. 68 (3): 391–401. - Michał Ginter - 2018.


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