Always a fun topic to talk or hear about, dinosaurs were the supreme rulers of the planet for a very long time before we came along. But with so many species spanning hundreds of millions of years, it’s hard to keep track of what happened to each one. But paleontologists take that as a challenge.
For a long time, the extinction of a certain group of aquatic dinosaurs that were basically ruling the oceans remained unsolved. Finally, after countless studies and disproved theories, a group of scientists revealed that the mystery behind the ichthyosaurus’ extinction was finally solved.
Similar to dolphins in build, the ichthyosaurus was kind of barrel-bodied, but very, very fast, efficient, and successful. They were air breathing swimmers, had muscular flippers and a tail fluke similar to that of a shark instead of that of a dolphin or whale – vertical instead of horizontal. They also birthed live offspring instead of laying eggs like most reptiles.
The ichthyosaurus ruled the oceans for over 150 million years with their agility, speed, and numbers. They disappeared 94 million years ago, and scientists so far only had theories about why that might have happened. Finally studying enough preserved fossils, researchers managed to figure out what happened.
Previous theories stated that the animals had already been in a decline for tens of millions of years before they were eventually out-competed by other ocean predators, like the mosasaurs. But studies show that the huge mosasaurs only appeared after the ichthyosauri were already extinct.
According to Valentin Fischer, one of the lead researches in the study,
We analyzed the extinction of this crucial marine group thoroughly for the first time. Ichthyosaurs were actually well diversified during the last chapter of their reign, with several species, body shapes, and ecological niches present.
But how and why did they disappear then?
As it turns out, there were two reasons – they couldn’t keep up in their evolution, as they had specialized too much, and the increasing temperatures of the world’s oceans left them without enough oxygen to keep on living. As the researches said in their paper,
Although the rising temperatures and sea levels evidenced in rock records throughout the world may not directly have affected ichthyosaurs, related factors such as changes in food availability, migratory routes, competitors, and birthing places are all potential drivers, probably occurring in conjunction to drive ichthyosaurs to extinction.
A growing body of evidence revealed that a major, global change-driven turnover profoundly reorganized marine ecosystems during the Cenomanian to give rise to the highly peculiar and geologically brief Late Cretaceous marine world.
Image source: Wikimedia