Article by: Adam Manning
Edited by: J. D. Dixon, Lewis Haller, and Harry T. Jones
Name: Helicoprion
Name Meaning: Spiral Saw
Age: Permian (Artinskian)
Diet: Carnivore
Size: ~ 6 m in length
Location: Kazakhstan, Australia, China, North America
Helicoprion was described in 1899 by Russian geologist Alexander Petrovich Karpinsky, who found remains in Kazakhstan. For just over a century, this freaky-looking Permian fish has caused a headache for palaeontologists who have tried to work out what on earth its spiral teeth were.
Helicoprion fossils date back to 290 million years ago, during the Artinskian Age of the Permian Period. We now know that Helicoprion was about 6 metres long. It is also a very widespread genus, having been discovered all over the world, including in Kazakhstan, Australia, China, and North America.
When Helicoprion was discovered it was based on a fragmentary fossil that only showed the animal’s bizarre teeth. Sharks and other cartilaginous animals are often only known from fragmentary fossils or just their teeth because their skeletal structure doesn’t fossilise well. The ‘saw’, or tooth-whorl, that Karpinsky first described wasn’t attached to any other remains, so he, nor anyone else, could be certain of where it was originally positioned on the body. Karpinsky initially proposed that they curled upwards from Helicoprion’s snout.
Over the years following Helicoprion’s discovery, many palaeontologists had other ideas regarding the purpose and position of the tooth-whorl. These theories include ideas such as the tooth-whorl originating from its back as a defensive display, as part of the dorsal fin, or being a part of its tail. In 1907, Oliver Perry Hay found a fossilised specimen that was preserved in its natural position, and because of this favoured the idea that it was a part of the jaw. Then, in 1950, Svend Erik Bendix-Almgreen discovered a Helicoprion tooth-whorl with cranial cartilage still present, again supporting the idea that at least some of the tooth-whorl was positioned inside the mouth. However, the position of the tooth-whorl within the jaw itself was still unclear.
It was only in 2013 with a paper authored by Tapanila et al. that the true workings of this strange animal were finally revealed. Using CT scans, Tapanila et al. showed that the tooth-whorl was fused into the lower jaw of the animal, and it would rotate and replace the teeth in the whorl throughout its life. When it closed its jaw, Helicoprion’s teeth would be pushed backwards, creating a fantastic slicing mechanism that could be used to slice through soft-bodied prey and push it further back into its mouth. Furthermore, the analysis done by Tapanila et al. showed that Helicoprion wasn’t a shark as previously thought, but a chimaera, also known as ratfish, a group of cartilaginous fish that diverged from sharks 400 million years ago.
So, after all, Helicoprion may not have been as bizarre as first thought, with teeth on its back or tail. Nevertheless, it is a testament to how advancing technologies and discoveries can help answer old questions and shed new light on forgotten mysteries.
Image References
[1] A fossilised Helicoprion tooth whorl. Click Here.
[2] Early reconstructions of Helicoprion, and the evolution of what palaeontologists believed it looked like. Illustrations by Darren Pepper.
Information References and Further Sources
[1] Chen, X., Cheng, L., and Yin, K. (2007). ‘The first record of Helicoprion Karpinsky (Helicoprionidae) from China’, Chinese Science Bulletin, 52 (16), pp. 2246-2251. DOI: https://doi.org/10.1007/s11434-007-0321-y. Accessed 13th October 2019. Click Here.
[2] Crew, B. (2013). ‘Prehistoric ghost shark Helicoprion’s spiral-toothed jaw explained’, Scientific American. Accessed 3rd September 2019. Click Here.
[3] Lebedev, O. A. (2009). ‘A new specimen of Helicoprion Karpinsky, 1899 from Kazakhstanian Cisurals and a new reconstruction of its tooth whorl position and function’, Acta Zoologica, 90, pp. 171-182. DOI: 10.1111/j.1463-6395.2008.00353.x. Accessed 3rd September 2019. Click Here.
[4] National Geographic. (2013). ‘Buzzsaw Jaw Helicoprion Was a Freaky Ratfish’. Available at: https://www.nationalgeographic.com/science/phenomena/2013/02/26/buzzsaw-jaw-helicoprion-was-a-freaky-ratfish/. Accessed 3rd September 2019. Click Here.
[5] Smithsonian. (Unknown). ‘Extinction Over Time’. Accessed 3rd September 2019. Click Here.
[6] Ramsay, J. B., Wilga, C. D., Tapanila, L., Pruitt, J., Pradel, A., Schlader, R., and Didier, D. A. (2015). ‘Eating with a Saw for a Jaw: Functional Morphology of the Jaws and Tooth Whorl in Helicoprion davisii’, Journal of Morphology, 276 (1), pp. 47-64. DOI: https://doi.org/10.1002/jmor.20319. Accessed 13th October 2019. Click Here.
[7] Tapanila, L., Pruitt, J., Pradel, A., Wilga, C. D., Ramsay, J. B., Schlader, R., and Didier, D. A. (2013). ‘Jaws for a spiral-tooth whorl: CT images reveal novel adaptation and phylogeny in fossil Helicoprion’, Biology Letters, 9 (2). DOI: https://doi.org/10.1098/rsbl.2013.0057. Accessed 13th October 2019. Click Here.
[8] Teichert, C. (1940). ‘Helicoprion in the Permian of Western Australia’, Journal of Paleontology, 14 (2), pp. 140-149. Accessed 13th October 2019. Click Here.