茄子直播

(all photos via Marc Laflamme)

茄子直播 prof unlocks mystery of an ancient mass extinction

University of Toronto Mississauga paleontologist Marc Laflamme spends his summers exploring the rocky red canyons of Namibia, searching for the faint fossilized remains of a long-extinct and very unusual creature.

Neither animal nor vegetable, the biotas of the Ediacaran period were the earliest large, complex life forms on the planet, dominating salt oceans for nearly 40 million years. Very little is known about the soft-bodied creatures, except that they mysteriously disappeared about 500 million years ago, and have no living relatives today.

While the life of the creatures remains something of a mystery, Laflamme and his colleagues may have unlocked the secret of how and why the Ediacarans died out at the beginning of the Cambrian period. Ecosystem engineering by newly-evolving animals radically changed the Ediacaran environmen, causing the demise of the unusual organisms. The team鈥檚 research is published in the .

The researchers examined three theories about why the Ediacaran creatures disappeared.

鈥淲e theorized that the disappearance of Ediacarans could be due to a lack of (fossil) preservation, a catastrophic mass extinction due to climate change, or something else,鈥 Laflamme says. The answer, to the team鈥檚 surprise, turned out to be the third option.

But before they could prove that theory, the team had to actually locate the fossils. The team looks for subtle tube-like impressions in the rocks by the soft-bodied organisms that lived on the floor of long-gone salt-water bodies.

photo of fossil

鈥淚t鈥檚 a challenge to find fossilized records,鈥 Laflamme says. There are about 50 sites around the world where Ediacaran fossils are found but, according to Laflamme, the Namibian site is a fossil bonanza.

鈥淚t marks the boundary of the Ediacaran world and the animal world, so we can study how ecosystems changed,鈥 he says.

Geochemistry ruled out the catastrophic mass extinction theory. 鈥淐onducting tests on the chemical composition of the rocks tells us if we were dealing with environments that were oxygenated or undergoing a stressful change,鈥 he says.

Positive results would have shown changes in ancient environments due to massive climate change, a volcanic activity or meteor impacts.

鈥淲e looked for evidence in the geochemistry, but our data didn鈥檛 show evidence of environmentally-driven extinction.鈥

But a different look at the fossil record revealed a surprising answer to their query, suggesting that 鈥渆cosystem engineering鈥 caused the Ediacaran to disappear.

鈥淓cosystem engineers are organisms that significantly alter their environment,鈥 Laflamme says. 鈥淐lams, for instance, can filter a lot of bacteria and nutrients out of the water, which causes problems for other creatures that need those resources. 

鈥淪omething came in and shook up the Ediacaran system,鈥 he adds. 鈥淲e hypothesized that it had to do with the evolution of new life, and asked ourselves, 鈥榃hat happens when you introduce new biology to a system?鈥欌

The researchers found fossil evidence of new animals 鈥 worms and worm-like animals 鈥 burrowing into sediment on the ocean floor.

 

 

鈥淲e can see trails all over the place, showing evidence of different behaviours like burrowing, feeding and den building,鈥 Laflamme says. 鈥淲e documented how new populations of Ediacaran biota responded to the presence of things that we knew, for sure, were animal fossils.鈥

鈥淭he new organisms would have disrupted the layer of bacteria along the sea floor that Ediacaran biota likely fed on,鈥 Laflamme says. 鈥淚t made it difficult for anything that didn鈥檛 move to survive.鈥

Delicate and sedentary, the Ediacarans couldn鈥檛 move or adapt, leaving them vulnerable to the effects of emerging new animals that disturbed the ocean environment. Unable to compete with the new animals for ecosystem space for nutrients, for space on the sea floor, and for food and oxygen, the biota were edged out by animals who were better adapted to use the available resources.

Laflamme鈥檚 research team included UTM graduate students Thomas Boag and Sara Mason. Funding was provided by Yale Peabody Museum of Natural History, NASA Astrobiology Institute, the Connaught Foundation, National Science and Engineering Research Council of Canada, National Science Foundation-Earth Sciences and the National Geographic Society.

 

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