The team compiled a list of more than 1000 species of vertebrates that lived in the 96-million-year interval straddling the mass extinction.
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Sallan, an assistant professor in Penn’s Department of Earth and Environmental Science in the School of Arts & Sciences stated, “Rather than having this thriving ecosystem of large things, you may have one huge relict, but otherwise everything is the size of a sardine”. For example because of being able to catch prey swiftly, the body size of specific group of species increases over time as a result of the positive evolutionary effects.
To sort out the body-size trends around the Hangenberg Event, Sallan and her coauthor, Andrew K. Galimberti, now a graduate student at the University of ME, amassed a dataset of 1,120 fish fossils spanning the period from 419 to 323 million years ago.
The researchers also looked at museum specimens, published papers and photographs to gather information on fish body sizes and found that the size of the vertebrates has increased during the Devionian period 419 to 359 million years ago. She found that the historical fish had been increasing in size over time – which is to be anticipated – but that body size plummeted after 97 percent of species were wiped out.
Study researcher and paleontologist Lauren Sallan, from University Of Pennsylvania, noticed that the fish that thrived 350 million to 323 million years ago during the Mississippian Period were smaller compared with their ancestors.
The prehistoric fish species during those times vary, as a few were as large as a school bus during this period and even if there were smaller vertebrates already thriving, most of these species measure at least one meter long. It killed off most of the big guys, according to a new study, and effectively shrunk most vertebrate species to the size of a human forearm or smaller. In addition, body size declined and continued downward for a long time after the event-for at least 40 million years. “In the aftermath of the extinction, that ends up being a bad strategy in the long term”.
Larger fish such as sharks are considered by many to be the kings of the seas, but by and large, it is smaller sea creatures that populate the Earth’s waters.
Still another idea, known as the Lilliput Effect, holds that after mass extinctions, there is a temporary trend toward small body size.
The authors believe their findings, which suggest that smaller, faster-reproducing fish had an evolutionary edge over their larger cousins in the disturbed, post-extinction environment, may have implications for the patterns we observe in current fish populations, many of which are struggling due to overfishing.
Instead, it had more ecological factors coming into play.
According to scientists, this mass extinction was the result of a global chill that brought glaciers to the tropics.
This pattern mirrors biological succession seen in plant species after a disturbance. She adds that this is an alarming issue because no one knows as to how long larger species may take to come back.
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Small vertebrates may possess an evolutionary edge that increased their odds for survival at the end of the Devonian.
