Climate change has long been viewed as a possible cause for the extinction of several species in recent years, but according new research, this environmental phenomenon has led to the death of an ancient group of marine reptiles as well.
In a study featured in the journal Nature Communications, a team of researchers, led by Valentin Fischer from the University of Liege and the University of Oxford, investigated the circumstances surrounding the extinction of an ancient reptilian creature known as the ichthyosaur.
While the exact era when this line of marine reptiles was extinguished is yet to be determined, Fischer and his colleagues said that a recent analysis suggests that the creatures likely met their end some 28 million years before the events that killed off other marine taxa during the end of the Cretaceous Period.
For years, scientists believed that ichthyosaurs became extinct as a result of the relatively low diversity among members of this marine predatory group.
This left the creatures vulnerable to even the slightest of changes in their environment such as an increase in competition with other aquatic animals at the time, or a reduction of diversity among their main food source, the belemnites, which were the ancient ancestors to modern-day octopuses and squids.
In their analysis of fossil records from the time of the ichthyosaurs, the researchers discovered that the marine reptiles were, in fact, well diversified toward the end of their reign, consisting of a number of species, body shapes and even ecological niches.
The team also found that there were no other marine reptiles large enough at the time that could have outmaneuvered them for available food sources. The only time other creatures became dominant was when the ichthyosaurs met their demise.
Fischer and his colleagues believe that the cause of the ichthyosaurs' extinction lies in their relatively low evolution rate. The marine reptiles were shown to be highly diverse during their reign, but after many ichthyosaur species died following the early Cenomanian period extinction event, the creatures' numbers severely diminished over time.
Contrary to earlier assumptions, the ichthyosaurs did not meet their end in an ecological vacuum, according to the researchers. The team found evidence that point to a high volatility in the environment of the world during the Cenomanian, such as a significant drop in sea levels and disruptions in geochemical cycles, which could have caused the marine reptiles to become extinct.
The Earth was vastly different before the Cenomanian environmental events occurred. There were no ice formations in the planet's poles, water levels in the seas were very high and global temperatures were at their highest.
The subsequent changes in the climate became too much for marine creatures, including the ichthyosaurs, to handle.
Fischer pointed out that even though ichthyosaurs may not have been directly impacted by the significant rise in sea levels and global temperatures at the time, they became vulnerable to other factors such as the resulting changes in migratory routes, spawning places, the availability of food and competition with other predatory creatures.
A combination of all these factors occurring at the same time likely drove the ichthyosaurs to their extinction.
Photo: Ryan Somma | Flickr
