About 66 million years ago, mammals were lucky. An asteroid bumped into what is now Chicxulub, Mexico, and launched a catastrophic chain of events that led to the destruction of non-bird dinosaurs. That day began his hairy climb to the top of a brave new world, the one from which our species would one day emerge . But little is known about the period immediately after the disappearance of the Cretaceous-Paleogene or the K-Pg event, because there is no fossil.
A team of paleontologists has discovered in Colorado a trail of thousands of fossils that provides an in-depth look at the first millions of years after the K-Pg mass extinction event. The discovery provides an insight into the interactions between animals, plants and the climate that emerged in the earliest days of the mammalian era, and allowed them to grow from the size of large rodents in the diverse wildlife we can begin to recognize today.
Dr. Leeson has been hunting fossils since the age of 10. Although he has discovered many dinosaurs, he has discovered fossils of species that appeared immediately after the extinction of dinosaurs proved to be quite elusive in his field of study.  "You can only find so many Trikeratop skeletons and partial skeletons of T. rex and stuff, until you want a bigger challenge," Dr. Lison said. "Finding fossils right after the K-Pg disappears is a huge, huge challenge."
In the spring of 2016, he and some colleagues explored a fossil site near Colorado Springs called Corral Bluffs. He knew years earlier Sharon Milito, a fan of fossil hunting, had discovered a mammal's skull, which was confirmed to be from the K-Pg border. He went looking for mammalian bones protruding from the ground. But his search proved fruitless.
While wandering through the bluff, he returned to his time as a graduate student working in South Africa. There he had learned to spot certain rocks, called concrements, that hold fossils in captivity, like pearls in oysters. He shifted his focus from the bones to the rocks.
"I found this ugly, white-looking rock that looked like a small mammalian jaw," Dr. Lison said. He opened it and found it inside a fossilized crocodile. "That was the moment when the bulb went out. If there is one fossilized concrete inside, there should be more more . "
He and his colleagues returned to Coral Bluff in September and searched for more ugly rocks.
"When I cracked open the first nodule I found in a mammal's skull," said Dr. Leeson.
It was the most complete mammal in the K-Pg interval he had ever seen. Four hours later they found Five have so far discovered more than 1,000 vertebrate fossils and 16 different mammalian species.
"With this discovery, we begin to see the whole skull of many of these mammals that we previously only knew from the teeth," says Stephen Chester, a mammalian paleontologist at Brooklyn College and author of the article.
Skulls While mammal-sized mammals survive the extinction event, raccoon-sized mammals die, and about 100,000 years after the K-Pg event, mammals recede as the mammal-sized mammals collapse. reappeared
About 300,000 years after the asteroid hit, more mammals appeared, such as Loxolophus and the small size of Carioptychus pigs. Within 700,000 years, capybara size Taeniolabis and wolf size Eoconodons began to flourish.
"You are going from a very small dog that you will see on the streets of New York to a very large wolf within these hundreds of thousands of years," says Dr. Chester.
The team also collected more than 6,000 fossils and Analyzes more than 37,000 pollen grains Together, the items describe the recurrence of plant life, which may have been a decisive factor in the evolution of mammals.
Ferns first appeared, with their feather-like leaves spreading in the wasteland in the continuation of many hundreds to several thousand years
Next, palm trees paraded in, dominating the green scene for hundreds of thousands of years.
Then, around 300,000 years after the disaster, a diverse array of nuts appeared . This coincided with a jump in the diversity and body size of herbivorous mammals, suggesting that they are an important food source.
"We call this world 'the world of pie pecans,'" says Ian Miller, a paleobotanist at the Denver Museum of Art. nature and science. He added that this era also coincides with a period of fossil warming, which may indicate that a shifting climate plays a role in the development of plants and animals after the event of extinction.
One of their most important botanical findings – a pod of fossil legumes – was made one summer by a student in high school while the team worked with NOVA for a documentary to be aired Wednesday, October 30 on PBS.
"It holds the world's earliest fossil legumes," Dr. Miller said. "She just smiled from ear to ear, totally radiant."
They date the bean plant about 700,000 years after the mass extinction. This period was associated with another short warming pulse as well as the appearance of wolf-sized mammals. Perhaps legumes feed on fluffy animals, according to the team.
"We liken them to the protein bars of the ancient world," says Dr. Miller. One of the remaining questions, he added, is whether climate has caused changes in plants and mammals. Courtney Spring, a geologist at the University of Florida, said she was impressed with their animal, plant and climate records.
Other paleontologists agreed.
"I looked at this and it went 'Aunt, these are many skulls!' "said Jailin Eberle, a vertebrate paleontologist at the University of Colorado in Boulder, who is not involved in the document. She said the next step should be to perform a micro CT scan of the skull, brain size determination and compartments which will provide an insight into the sensory abilities of animals .
The finding also helps to clarify how species are able to respond to catastrophic events in a relatively quick time frame.
"There are obvious implications for present biodiversity the climate crisis as we begin to approach similar levels of devastation, "says Anjali Goswami, a paleontologist on vertebrate animals at the Natural History Museum in London. The current crisis, she added," is unfortunately caused by our shortsightedness, but from a chance encounter with an alien body. "