The same was true of prehistoric sharks, although some took this curved conveyer belt tooth row to an extreme! The ‘whorl toothed sharks’ were an extremely unusual group that swam in the oceans from 323 to 247 million years ago (the earliest dinosaurs appear on land at around 250 million years ago).
Helicoprion is well-known from fossils from North America and Russia, but few people are aware of its Yorkshire ancestor! One of the earliest whorl toothed sharks is from Carboniferous aged rocks (around 320 million years old) near Brockholes just south of Huddersfield. This beautiful specimen was described as a new species, Edestus newtoni, in 1916. Edestus is unique in having a curved tooth row on both the upper and lower jaw – as our Huddersfield specimen has only one jaw it has been suggested that it might belong to a different genus, Lestrodus, instead (Tapanila et al 2019).
The function of the tooth whorl of Helicoprion, Edestus, and their relatives has been the subject of many different artistic reconstructions throughout the decades – was it the upper jaw? Lower jaw? Both jaws? Spiky fin spine? Could the tooth row unroll like a whip? These different interpretations were famously summarised by the artist Ray Troll: It is now fairly accepted that the tooth whorl formed part of the lower jaw in these sharks, however variation in tooth whorl shape between different species means there is still much debate about how these animals fed. Research published in 2015 by Ramsay et al. analysed the forces on the tooth whorl of Helicoprion and found that it was well adapted to eating animals like ammonites with a soft body in a hard shell. The circular nature of the tooth row creates forces on the prey in different directions simultaneously – the front teeth would push the shell away whilst the back teeth pull and cut the soft body into the mouth. Other interpretations include the outer teeth slashing prey, the upper and lower jaw cutting prey like scissors, or the bottom jaw moving backwards and forwards like a saw (Itano 2019). The tooth whorl of Edestus highlights the ever-changing nature of palaeontological science, constantly refining and adapting ideas based on new techniques and new discoveries. How do you interpret these fossils? What was the function of these teeth? Come by the Fossils in t’Hills stall at one of our upcoming events and have a go at your own reconstruction! Author: Rebecca Bennion References
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