Of all the terrifying things that have ever lived in the ocean, mosasaurs hold a special place in my heart. Admittedly, the similarity between the name of the biggest mosasaur species – Tylosaurus – and my own may play a small role. But mostly it’s because they are the original sea monsters. Although more closely related to snakes and iguanas than dinosaurs, these giant aquatic lizards had huge heads full of terrifying teeth that would put Tyrannosaurus rex to shame. (Literally: when it comes to skull size, mosasaurs easily outrank any land-based carnivore you care to name.) And if ruling the oceans weren’t enough, this week scientists revealed that at least one species of mosasaur had adapted itself for inland river systems as well.