Fossils show quick rebound of life after the 'Great Dying'

Fossils including sharks, sea reptiles and squid-like creatures dug up in Idaho reveal a marine ecosystem thriving relatively soon after Earth's worst mass extinction, contradicting the long-held notion life was slow to recover from the calamity.

Artistic view of the diversified and complex Early Triassic marine ecosystem of southeastern Idaho 
as revealed by the Paris Biota. Illustration by and with permission of Jorge Gonzalez 
[Credit: Jorge Gonzalez]

Scientists on Wednesday described the surprising fossil discovery showing creatures flourishing in the aftermath of the worldwide die-off at the end of the Permian Period about 252 million years ago that erased roughly 90 per cent of species.

Even the asteroid-induced mass extinction 66 million years ago that doomed the dinosaurs did not push life to the brink of annihilation like the Permian one.

View of a sampled slab from the Paris Biota showing abundant fish scales and shrimp 
[Credit: Arnaud Brayard]

The fossils of about 30 different species unearthed in Bear Lake County near the Idaho city of Paris showed a quick and dynamic rebound in a marine ecosystem, illustrating the remarkable resiliency of life.

"Our discovery was totally unexpected," said paleontologist Arnaud Brayard of the University of Burgundy-Franche-Comte in France, with a highly diversified and complex assemblage of animals.

Remarkable group of sponge fossils from the Paris Biota under UV light. 
Scale bar lenght: 5mm [Credit: Arnaud Brayard]

The ecosystem from this pivotal time included predators such as sharks up to about two metres, marine reptiles and bony fish, squid-like creatures including some with long conical shells and others with coiled shells, a scavenging crustacean with large eyes and strangely thin claws, starfish relatives, sponges and other animals.

The Permian die-off occurred 251.9 million years ago. The Idaho ecosystem flourished 1.3 million years later, "quite rapid on a geological scale," according to Brayard.

The Paris Biota illustrates the oldest occurrence of derived characters in several clades and it shows that 
at least some Early Triassic marine communities include ancient lineages in the lowest trophic levels 
together with newly-evolved groups occupying higher trophic levels 
[Credit: Carla Schaffer/AAAS]

The mass extinction's cause is a matter of debate. But many scientists attribute it to colossal volcanic eruptions in northern Siberia that unleashed large amounts of greenhouse and toxic gases, triggering severe global warming and big fluctuations in oceanic chemistry including acidification and oxygen deficiency.

The Idaho ecosystem, in the earliest stages of the Triassic Period that later produced the first dinosaurs, included some unexpected creatures. There was a type of sponge previously believed to have gone extinct 200 million years earlier, and a squid-like group previously thought not to have originated until 50 million years later.

A graphic detailing how the Early Triassic was an epoch that recorded major extinctions 
and geochemical perturbations [Credit: Arnaud Brayard & Gilles Escarguel]

The researchers found bones from what could be the earliest-known ichthyosaur, a dolphin-like marine reptile group that prospered for 160 million years, or a direct ancestor.

"The Early Triassic is a complex and highly disturbed epoch, but certainly not a devastated one as commonly assumed, and this epoch has not yet yielded up all its secrets," Brayard said.

The research was published in the journal Science Advances.

Source: Australian Associated Press [February 18, 2017]