Evrim Yazgin
Cosmos science journalist
Palaeontologists have identified a new species of ichthyosaur from a partial skeleton found on New Zealand’s South Island.
Ichthyosaurs are marine reptiles that evolved about 250 million years ago. Though they resemble dolphins, they have a completely different evolutionary lineage. They swam the oceans while dinosaurs ruled on land, dying out about 94 million years ago.
The New Zealand ichthyosaur was found on the Coverham Station farmstead in the Canterbury region, about 200km northeast of Christchurch.
Rocks from this region of the Clarence Valley date to the Cretaceous period (141–66 million years ago) when the area formed the bed of an ancient sea. The ichthyosaur fossil is 98 million years old.
Back then, New Zealand itself was further south and was part of the supercontinent Gondwana, joined with Australia, Antarctica and South America.
Marine reptiles from the “Age of Dinosaurs” have been found in New Zealand before. Among them is the oldest known marine reptile found in the southern hemisphere. But the new species provides a rare glimpse into ichthyosaurs of Eastern Gondwana. It is the first ichthyosaur found on New Zealand’s South Island.
The fossil is also the most completely preserved individual ichthyosaur found in New Zealand.
“It possesses a well-preserved pelvis and hindfin which have added to the known dataset of these elements which are so rarely preserved in Cretaceous species,” the researchers write in their paper published in the Journal of Vertebrate Palaeontology.
The fossil was originally found in 2010 and was tentatively assigned to the species Platypterygius australis known from Australian fossils.
Three-dimensional scans of the ichthyosaur’s bones reveal that it is a unique platypterygiid species. Members of this group grew to 7m long.
While closely related to P. australis, slight differences in the New Zealand specimen suggest a more diverse speciation of this group of ichthyosaurs in Eastern Gondwana than previously thought.
The researchers also say that the species appears unrelated to ichthyosaurs of Western Gondwana known from South America, “suggesting potential regionalism amongst the Gondwanan Cretaceous ichthyosaur populations”.
