New Fossil Treasure Documents Life Recovering on Earth After Dinosaur-Killing Asteroid Impact

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October 24, 2019

CGI rendering of Taeniolabisan ancient mammal, from the PBS NOVA special, “Rise of the Mammals”.HHMI Tangled Bank Studios

Scientists have discovered an extraordinary collection of fossils that reveal in detail how life recovered after a catastrophic event: the impact of an asteroid that wiped out the dinosaurs 66 million years ago at the end of the Cretaceous . Described in an article published Oct. 24 in the journal Science, the unprecedented discovery – thousands of exceptionally preserved animal and plant fossils from the first million years after the disaster – sheds light on how life emerged of one of Earth’s darkest hours.

Scientists found this new record of the first million years after the asteroid impact in the region around Colorado Springs, Colorado, which is part of a larger geological province known as the Denver Basin . The discovery includes both plants and animals, painting a portrait of the emergence of the post-dinosaur world.

The team behind this discovery was led by two scientists from the Denver Museum of Nature & Science, lead author Tyler Lyson, curator of vertebrate paleontology, and co-author Ian Miller, curator of paleobotany and Director of Earth and Space Sciences. Among the co-authors is Greg Wilson, professor of biology at the University of Washington and curator of vertebrate paleontology at the Burke Museum of Natural History & Culture, who joined the team as an expert on mass extinction. of the Cretaceous and the evolution of mammals in its aftermath.

Skulls of extinct mammals

An aerial view of the prepared mammalian skull and lower jaw fossils recovered from Corral Bluffs.HHMI Tangled Bank Studios

“I’ve been working on this time period and these mammals for 21 years, and it’s really an exceptional window into this pivotal event in the history of life,” said Wilson, who was a curator at the Denver Museum of Nature & Science before. joining the UW faculty in 2007. “We go from dinosaur-dominated terrestrial ecosystems to becoming mammal-dominated in the geological blink of an eye.”

“The course of life on Earth changed dramatically in a single day 66 million years ago,” Lyson said. “By blowing up our planet, an asteroid triggered the extinction of three out of four types of living organisms. While it was a very bad time for life on Earth, some things survived, including some of our earliest ancestors.

A moment of serendipity paved the way for these rare fossil discoveries. Lyson, who was unsuccessfully searching for post-impact vertebrate fossils, was inspired by a fossil in a museum drawer and fossil-hunting techniques used by colleagues in South Africa. In the summer of 2016, he stopped looking for shiny bits of bone in the Denver Basin and instead focused on egg-shaped rocks called concretions.

Opening up the concretions, Lyson and Miller found fossils such as the skulls of mammals from early generations of survivors of the mass extinction. Since most of what is understood from this time is based on tiny fossil fragments, such as bits of mammalian teeth, finding a single skull would be exceptional. Lyson and Miller found four in a single day and more than a dozen in a week. So far, they have found fossils of at least 16 different mammal species.

Fossilized plants

An aerial view of selected plant fossils recovered from Corral Bluffs.HHMI Tangled Bank Studios

Wilson participated in excavations at Corral Bluffs, a site just east of Colorado Springs. He and co-author Stephen Chester, an assistant professor at Brooklyn College at the City University of New York, worked to identify the mammal fossil the team found, calculate changes in body size over time, and analyze the diversity of species after the asteroid impact. The researchers determined that just 100,000 years after the cataclysm, the diversity of mammals had approximately doubled. 300,000 years after the impact, maximum mammalian body mass had tripled, and mammals were developing specialized diets, possibly in response to changes in plant diversity.

These discoveries illustrate how the Denver Basin site also adds evidence to the idea that the recovery and evolution of plants and animals were intertwined after the asteroid impact. More than 6,000 leaf fossils were collected as part of the study to help determine how and when Earth’s forest rebounded after the mass extinction event. Combining a remarkable record of fossil plants with the discovery of fossil mammals allowed the team to link millennial periods of warming to specific global events, including massive amounts of volcanism on the Indian subcontinent.

A skull of an extinct mammal

A skull of a Taeniolabis taoensisa herbivorous mammal, discovered at the Corral Bluffs fossil site. Taeniolabis appears about 700,000 years after the mass extinction at the end of the Cretaceous, around the same time as the oldest legume fossil in the world.HHMI Tangled Bank Studios

These events may have shaped ecosystems on the other side of the world. For example, the research team found another increase in mammalian body size about 700,000 years after the impact, which coincided with the evolution of legumes and then a new type of plant. Further analyzes of these fossils, as well as the unearthing of new specimens, will only deepen scientists’ understanding of this critical period in Earth’s history and the evolution of mammals that preceded humans. .

“Our understanding of the aftermath of the asteroid has been patchy,” Lyson explained. “These fossils tell us for the first time exactly how our planet recovered from this global cataclysm.”

Additional co-authors include David Krause, James Hagadorn, Antoine Bercovici, Farley Fleming, Ken Weissenburger with the Denver Museum of Nature & Science; William Clyde and Anthony Fuentes with the University of New Hampshire; Kirk Johnson and Rich Barclay with the Smithsonian Institution’s National Museum of Natural History; Matthew Butrim of Wesleyan University; Gussie Maccraken at the University of Maryland; and Ben Lloyd of Colorado College. The research was funded by the Lisa Levin Appel Family Foundation, M. Cleworth, Lyda Hill Philanthropies, David B. Jones Foundation, ML and SR Kneller, T. and K. Ryan and JR Tucker as part of the Denver Museum of Nature & Science No Walls: school initiative.

For more information, contact Wilson at [email protected].

Adapted from a press release from the Denver Museum of Nature & Science.

Tag(s): Burke Museum of Natural History & Culture • College of Arts & Sciences • Department of Biology • dinosaurs • evolution • Gregory Wilson Mantilla • paleontology