Welcome to my latest blog post. This one is going to have a look at a new big and bad ichthyosaur as well as what this actually means in a bigger picture. The paper I am looking at is by Fröbish et. al. and was published this year.
The authors of the paper describe a new ichthyosaur from the early Middle Triassic (244 million years old) which they have named Thalattoarchon saurophagis. The specimen they examined comprises most of the skull and axial skeleton, parts of the pelvic girdle (hips) and parts of the hind limbs. The ichthyosaur is very large, estimated to be larger than 8.6 metres long. This is about the same size of a modern killer whale which is awesome.
However, the size is not the coolest thing about this specimen. By far the best aspect (to my mind) of this specimen is the teeth. The teeth are labiolingually flattened with two cutting edges and are slightly recurved. This just means that they are flatted and sharp, similar to those of a shark, but without a serrated cutting edge (Fig. 1). Furthermore, the largest tooth measures a minimum of 12cm tall from root to tip with a crown of 5cm.
The flattened teeth is an unusal feature of ichthyosaurs. The vast majority of ichthyosaurs have conical teeth, ideally adapted to piercing and holding onto small prey items such as fish or belemnites (an ancient squid-like beastie). The flattened teeth suggest a different prey type. The teeth are designed for cutting through flesh and indicate that this ichthyosaur was capable of attacking and eating prey of a similar size to its self. Ichthyosaurs with conical teeth would likely swallow their prey whole as unlike this one, they would have been unable to cut and bite through flesh.
So despite being very cool, is it such a big deal that this ichthyosaur is big and capable of eating large prey? Well, there’s more to this story than that. A short time (in geological time anyway) before this specimen was alive, one of the biggest extinction events in Earth’s history had just taken place, the Permian – Triassic extinction, where an estimated 96% of ALL LIFE in the sea died. Crazy huh! It takes time for life to recover, and in terms of trophic groups (levels in a food chain, eg producer, grazer, predator, scavenger etc) this starts from the bottom up where producers and grazers would recover first with predators recovering from an event like this last. The ichthyosaur in this paper would sit at the highest trophic level as top predator. The presence of this specimen means that the oceans had recovered from this huge extinction event. This indicates a rapid evolution and recovery in the seas. The seas recovered within 8Ma of the extinction event and only 4Ma after reptiles first invaded the seas. This is a faster recovery than previously expected. Up until this point, the modern trophic network in the seas had not been properly established with large predatory tetrapods at the top of the food chain.
So there you go. New specimens and new species are always very interesting and usually pretty damn cool but it is also important to think of the bigger picture and the implications that a specimen may have.
As ever, thanks for reading. Until next time fossil fans!
Fröbish, N. B., Fröbish, J., Sander, M., Schmitz, L. & Rieppel, O. 2013. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks. PNAS. 110(4):1393-1397