A new species of Early Cretaceous ichthyosaur has been named and described following the study of fossilised remains found in Columbia. The fossils had previously been assigned to the ophthalmosaurian Platypterygius, but researchers from Canada, Germany and Columbia have erected a new species Kyhytysuka sachicarum.
An examination of the teeth in the jaws of the 94-cm-long skull, found that the anterior teeth were small whilst the teeth towards the back of the jaw were much bigger and robust. The researchers, who include Hans Larsson (Director of the Redpath Museum at McGill University), conclude that this ichthyosaur evolved unique dentition that enabled it to despatch large prey such as other marine reptiles.
The First Ichthyosaur Fossils from Columbia to be Described
The fossil specimen, consisting of a relatively uncrushed skull, preserved in three-dimensions, was the first definitive ichthyosaur material to have been found in Columbia (Paja Formation). The material was compared to other South American ichthyosaur fossils and assigned to the Platypterygius genus, being formally described and assigned to a new species – P. sachicarum in 1997.
Writing in the “Journal of Systematic Palaeontology”, the research team concluded that this fossil should really be placed in its own separate genus. The name Kyhytysuka translates from the ancient Muisca culture of central Columbia as “the one that cuts with something sharp”, a nod to the heterodont dentition in the jaw.
Hans Larsson explained:
“This animal evolved a unique dentition that allowed it to eat large prey. Whereas other ichthyosaurs had small, equally sized teeth for feeding on small prey, this new species modified its tooth sizes and spacing to build an arsenal of teeth for dispatching large prey, like big fishes and other marine reptiles.”
A Columbian Researcher Assists with the Study
This is an exciting opportunity for graduate researcher and co-author Dirley Cortés, who hopes to be able to continue to study Columbian marine reptiles, as she grew up in the mountainous area of Columbia close to where this fossil was discovered.
A Fearsome Predator
The dentition of Kyhytysuka sachicarum is unique among ichthyosaurs. This ichthyosaur had heterodont dentition (teeth of different shapes and sizes in the jaw), the teeth at the front of the jaw were small and designed to pierce, further along the jaw the teeth were larger, and adapted to cut flesh, whilst teeth at the back of the jaw were more robust and better at crushing. These teeth and other skull adaptations imply that Kyhytysuka evolved as an apex predator specialising in the hunting and consuming of large vertebrates such as fish and other marine reptiles. As such, this is the first example of a Cretaceous hypercarnivorous ichthyosaur. A hypercarnivore is defined as an organism whose diet consists of at least 70% meat.
The scientific paper: “Re-appearance of hypercarnivore ichthyosaurs in the Cretaceous with differentiated dentition: revision of ‘Platypterygius’ sachicarum (Reptilia: Ichthyosauria, Ophthalmosauridae) from Colombia” by Dirley Cortés, Erin E. Maxwell and Hans C. E. Larsson published in the Journal of Systematic Palaeontology.