Study Sheds New Light on Fossil of Extinct Dolphin-Like Reptile That May Have Lived 100 Million Years Ago

A remarkable fossil of a dolphin-like marine reptile, the ichthyosaur fossil, originating from the North Canterbury area in New Zealand, is offering an unprecedented glimpse into an extinct marine reptile that swam in ancient seas almost 100 million years ago, new research published in the Journal of Vertebrate Paleontology stated. The discovery, by paleontologist James Crampton, in 2010, is the most complete ichthyosaur skeleton found in New Zealand. Initially caught at Coverham Station in Clarence Valley inside a solid concretion and later brought on to GSN Science, where they rested on the shelves without a name. Initial identification by one scientist classified them as an Ichthyosaur due to characteristics typical of an hourglass-looking, shape-shaped vertebra; its true origin remained a secret for over one decade.

"This discovery is particularly exciting because the specimen is about 98 million years old. This is about four million years before the final extinction of ichthyosaurs, which makes it one of the youngest semi-complete ichthyosaur skeletons known," the researchers note in their study, according to The Conversation.

It is exceptionally well preserved, with a skull base, pectoral girdle elements, anterior paddle elements, and a complete left pelvis—all extremely rare for Cretaceous ichthyosaurs. Advanced medical CT scanning has now been used to make highly detailed 3D renderings of the bones that reveal previously invisible features of this ancient marine reptile. This has been a critical breakthrough, as New Zealand ichthyosaurs have always been poorly known owing to the scarcity of well-preserved specimens.

Surprising results about some evolutionary relationships were discovered. This specimen shared a close relationship with the Platypterygius australis species known from the Australian waters, along with some Cretaceous European species. It is surprisingly not related to ichthyosaurs from Western Gondwana, now South America, although these two regions were very close neighbors during the Late Cretaceous, according to Greek Reporter. This regional distinction is especially interesting to paleontologists. Several peculiarities have been found in this fossil, including an extremely simplified skull base and a shoulder blade of peculiar shape. Perhaps most notably, it possesses a unique furrow on one of its pelvic bones—a characteristic not observed in any other known ichthyosaur species.

The discovery represents a major milestone in our understanding of the diversity of marine reptiles from the Southern Hemisphere. Before this find, New Zealand's only Cretaceous ichthyosaur remains consisted of fragmentary jaw pieces and vertebrae—all recovered from different locations in the North Island. First appearing around 250 million years ago, ichthyosaurs evolved from what may have been a crocodile-like ancestor to develop a distinctive fish-like form convergently resembling modern dolphins. They persisted right up until their extinction, some 94 million years ago, making this specimen one of the last of its kind to swim in Earth's ancient oceans, as per The Conversation.