The mysterious causes of a disappearance

These are results that really change how the situation is looked at. The major extinction of ichthyosaurs did not take place during the Jurassic. On the contrary! During this period, even if other marine animals did indeed disappear, our reptiles were in great shape.

Five to six different genera in reality continued to cohabit, before definitively disappearing during the end of the Cretaceous, around 94 million years ago. A pretty brutal end to existence. As a result, this ‘second extinction’ only becomes all the more severe...and still as mysterious. The appearance of ‘modern’ fishes, even if it certainly had an effect, cannot in itself be sufficient to explain their decline. No more than the decline of the belemnites (types of small cuttlefish on which the ichthyosaurs fed).

The explanation may actually be a broader one. Valentine Fischer has put his finger on an important event, of which the extinction of ichthyosaurs was in the end just one aspect. ‘During the same era all the marine groups seem to have been affected by a remarkable event. Even the plants underwent some changes.’ An event that is difficult to determine for the moment. Maybe the advent of humid tropical forests? Or one of the numerous climatic and oceanographic changes which took place during this period, which was without a doubt the warmest throughout the whole of geological history? Or perhaps the mechanisms involved in collisions between continents? No-one knows yet. ‘There are so many hypotheses...It is impossible to give the exact cause.’

The next step: identifying this mysterious event...