Scientists have identified a new species of mosasaur, a family of marine reptiles that lived during the age of dinosaurs, named Tylosaurus rex. This formidable creature, whose name means 'King of the Tylosaurs,' could grow up to 43 feet (13.1 metres) in length, making it more than twice the size of the largest great white sharks and comparable to the land-based Tyrannosaurus rex.
According to palaeontologists, Tylosaurus rex possessed exceptionally strong neck and jaw muscles, along with a mouth full of razor-sharp, finely serrated teeth. These adaptations would have made it a top predator in the seas that covered what is now Texas around 80 million years ago. 'Everything is bigger in Texas, and that includes the mosasaurs, apparently,' said lead researcher Dr Amelia Zietlow from the American Museum of Natural History.
The fossil remains of Tylosaurus rex had been sitting in several museums across the United States for decades, misidentified as another species. Dr Zietlow stumbled upon a mislabelled fossil in the archives of the American Museum of Natural History, which had been labelled as Tylosaurus proriger, a larger mosasaur discovered over 150 years ago. However, upon comparison with the holotype, it became clear that this fossil was something different. The mysterious mosasaur was much larger than Tylosaurus proriger, with a skull almost as big as Dr Zietlow herself, and it originated from Texas rather than Kansas, dating back four million years later.
Dr Zietlow and her colleagues soon realized they had discovered a previously unrecognized species, which included more than a dozen similarly mislabelled fossils held at various institutions. Their holotype specimen for the new species is a giant specimen nicknamed 'The Black Knight,' first discovered in 1979 along an artificial reservoir near Dallas.
In a paper published by the Bulletin of the American Museum of Natural History, scientists state that Tylosaurus rex would have been the 'top predator of its domain.' At that time, North America was nearly divided in half by the Western Interior Seaway, a warm shallow sea that submerged much of Texas. This environment was home to a variety of sea monsters, including sea turtles, mosasaurs, plesiosaurs, and fish. Dr Zietlow noted that T. rex did not appear to have a specialized diet, unlike other mosasaurs, as its teeth were not clearly adapted for one specific type of prey.
'Tylosaurus rex differs from other Tylosaurus in part by having serrated teeth and features of the skull that suggest stronger jaw and neck muscles,' said Dr Zietlow. 'I think it was using those tools to help it process larger prey by ripping things to pieces.'
Furthermore, Tylosaurus rex was not only a danger to other creatures but also to members of its own species. Mosasaurs in general seemed to have been aggressive towards one another, with evidence of violence within this species to a degree not previously seen in other Tylosaurus specimens. Ron Tykoski, vice-president of science and curator of vertebrate palaeontology at the Perot Museum, explained that besides being huge, T. rex appeared to be a much meaner animal. The Black Knight specimen shows signs of massive wounds, including a missing snout tip and a fractured jaw, which researchers believe could only have been inflicted by another member of its own species.
This discovery not only offers a fascinating glimpse into a terror from the distant past but also helps clarify the evolutionary history of mosasaurs. Mosasaurs have often been considered a 'boring' group with limited diversity, but this study reveals an unexpectedly complex picture. Dr Zietlow added, 'I think it shines a spotlight on how diverse mosasaurs as a group really are. We have identified many new features of mosasaur anatomy. When taken into account in our analyses of their evolutionary relationships, they paint a very different picture than what was known for the last 30-ish years.'
