Global warming and a lack of evolutionary prowess led to the extinction of a group of marine reptiles similar to a dolphin, named ichthyosaurs, that thrived in the oceans of the Earth until their relatively abrupt demise about 94 million years ago, according to a new research report cited by Reuters.

Previously, scientists had thought the ichthyosaurs had been driven to extinction by other ocean-going predators, such as the monstrous lizard-like monasaurs, that had out-competed the reptiles for food over tens of millions of years.  The new research shows the monasaurs were just arriving to the prehistoric party by the time the ichthyosaurs met their demise.

Ichthyosaurs came upon the scene about 248 million years ago and quickly became the dominant player in the world’s oceans as the dinosaurs were the kingpins on the land.  The air-breathing reptiles were fast and efficient swimmers with streamlined bodies and vertical tail flukes like sharks.  They were blessed with very large eyes that enabled them to hunt in deep and dark waters, searching for fish and squid, their primary diet.  Ranging from less than three feet long to as much as 70 feet in length, they gave birth to live offspring instead of laying eggs.

Pouring over fossil records and climate information, the researchers tried to examine all the evidence that may have led to the extinction of the ichthyosayrs.  The records indicated the Earth was undergoing a rapid warming period, one of the hottest periods in the last 250 million years, and that led to major fluctuations in sea levels and temperatures.

Likely, there were large patches of the ocean floor that were depleted of oxygen due to the warmer temperatures and many species were unable to live in the changing conditions.  This may have led to alterations in the migratory habits and the spawning areas used by the ichthyosaurs, as well a limiting the availability of their food sources.  The researchers noted other marine creatures, such as relatives of the modern squid and prehistoric clams also recorded major losses in the same period.

These factors, coupled with the creatures inability to evolve to the changing climate conditions, eventually led to the marine predators extinction, according to the researchers.  The findings of the study can be found in the journal Nature Communications.