A team of researchers, led by Dean R. Lomax from the University of Bristol and the University of Manchester in the UK, recently published a study in the open-access journal PLOS ONE. They discovered a new species of ichthyosaur, a type of ancient marine reptile, that was likely the largest marine reptile ever formally described.

Over the past few years, Lomax and his research team found and collected fragments of an ichthyosaur jawbone from the Westbury Mudstone Formation in Somerset, UK. The new bone was similar in size and shape to another jawbone found in the same rock formation, just a few kilometers away. The researchers now believe these two jawbones belong to a previously undescribed species of ichthyosaur, a group of huge reptiles that lived in the oceans during the age of the dinosaurs.

Based on the size of these bones, the new species, named Ichthyotitan severnensis, could have measured up to 25 meters long – twice the length of a city bus! However, since the description of this new species is based only on limited bone fragments, the study authors note that more paleontological evidence is needed to confirm the likely size of I. severnensis.

The holotype of Ichthyotitan severnensis gen. et sp. nov., a recently collected specimen (BRSMG Cg3178) comprising a very large, but incomplete right-hand surangular
The holotype of Ichthyotitan severnensis gen. et sp. nov., a recently collected specimen (BRSMG Cg3178) comprising a very large, but incomplete right-hand surangular. Credit: Dean R. Lomax et al. / PLOS ONE

Ichthyosaurs first evolved in the early Triassic period, about 250 million years ago. Within a few million years, some ichthyosaurs had evolved to be at least 15 meters long, and by the late Triassic (around 200 million years ago), the largest ichthyosaurs had evolved, including the newly described I. severnensis.

But this reign of giant ichthyosaurs did not necessarily last long. While some species of ichthyosaurs continued to roam the oceans for millions of years, these “gigantic ichthyosaurs” are believed to have gone extinct during the Triassic-Jurassic extinction event around 200 million years ago, and this unique group of marine reptiles never again reached such massive sizes.

As lead author Dean Lomax explains, his team had hoped to uncover another giant ichthyosaur jawbone like the one they studied in 2018. This new, more complete specimen shows they now have two of these unique, giant “surangular” bones, providing tantalizing evidence that complete skulls or skeletons of these ocean giants may one day be found.


Sources

Public Library of Science | Lomax DR, de la Salle P, Perillo M, Reynolds J, Reynolds R, Waldron JF (2024) The last giants: New evidence for giant Late Triassic (Rhaetian) ichthyosaurs from the UK. PLoS ONE 19(4): e0300289. doi.org/10.1371/journal.pone.0300289


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