For years now, scientists have agreed upon five recognised mass extinctions that are said to have wiped out life on our planet in the distant past. New research, though, has suggested that a sixth one is added to the club of the famous five: the Capitanian extinction that is believed to have occurred 260 million years ago. The findings have been published in the Geological Society of America Bulletin.
We are used to hearing about five large-scale annihilation events only, specially those theories pertaining to the dying out of the dinosaurs. Science, though, has proved how much a dynamic field of study it is: ever-changing as more information is gleaned by scientists. As such, findings of a new study suggest that a sixth massive extinction known as the Capitanian extinction should be added to the list.
In fact, its pertinence was brought to the attention of the world of science more than two decades ago. The Capitanian extinction is said to have happened in the Middle Permian time, 262 million years back. The theory was proposed when fossils in rock formations argued to be the evidence of a massive extinction in China were discovered.
However, the relevance of the Capitanian extinction with respect to the list of five recognised extinctions remained a controversial subject. This was due to the fact that the data obtained was taken only in tropical latitudes while evidence from higher latitudes were lacking. Therefore, scientists argued that the event might have been a localised one, and not a massive one entailing many regions of the globe. It was also added that the Capitanian extinction might have marked the beginning of the Permian extinction, and not constituted a large-scale annihilation on its own.
Scientists from the University of Hull and the University of Leeds have now changed the perspective after they analysed marine fossil ranges in the Kapp Starostin Formation of Spitsbergen, an island which is part of the Norwegian archipelago Svalbard.
Brachiopods in a rock formation in Spitsbergen, Norway. The species is said to have disappeared in a massive extinction event 260 million years ago. Photo credits: Paul Wignall; University of Leeds
The fossils that received the attention of the researchers were left by invertebrate marine animals that emerged at the start of the Cambrian period, 570 million years ago, known as brachiopods. These fossils were found to suddenly disappear for a period of time.
“They all drop out,” co-author Paul Wignall said in a statement. “It’s like a blackout zone and there’s nothing around.”
After the sudden disappearance, a few species seemed to recover. This was then followed by a great increase in molluscs that happened 8 million years prior to the next mass event, the Permian extinction which erased 97 % of the known species of that time.
The researchers interpreted this finding as an indication of two severe brachiopod extinctions in the Middle to Late Permian, with a recovery stage in between.
Moreover, the first of the two was probably in the Capitanian, according to dating techniques used by the team. This would imply that the Capitanian might indeed be the 6th massive extinction.
“It’s the first time we can say this is a true global extinction,” explained lead author David Bond.
Bond is of the opinion that the magnitude of the Capitanian extinction would be comparable to the well-known end-Cretaceous mass extinction that is associated with the wiping out of dinosaurs.
The reason for the sixth mass extinction has been suggested to be anoxia: low concentrations of oxygen. This might be the case because the event appears to be coinciding with a massive oxygen depletion.