How mammals recovered after dinosaur extinction


This 2017 video is about Paleogene animals.

By John Pickrell in Science News, October 24, 2019 at 2:00 pm:

Remarkable fossils capture mammals’ recovery after the dino-killing asteroid

Survivors grew from the size of a rat to that of a wolf within 700,000 years of the impact

Understanding how life rebounded after an asteroid strike 66 million years ago, which wiped out up to 75 percent of Earth’s species and ended the dinosaurs’ reign, has been hard. Fossils from the immediate aftermath are exceedingly rare (SN: 4/2/19). Now, though, a fossil-rich deposit in Colorado’s Denver Basin is offering paleontologists a window into how mammals, plants and reptiles recovered and flourished following the impact.

The find has allowed the scientists to piece together a detailed timeline of how mammals quickly diversified and grew in size once nonavian dinosaurs were out of the way. Within 700,000 years after the impact, for instance, some mammals had grown to be 100 times as heavy as the original survivors, researchers report online October 24 in Science.

“This is one of those discoveries all paleontologists dream of,” says Steve Brusatte, a paleontologist at the University of Edinburgh who was not involved in the research. “With a snap of a finger, mammals took over from the dinosaurs. More than 150 million years of dinosaur dominance was ended, just like that, and our ancestors took over.”

The Corral Bluffs site in the Denver Basin is the only known locality in the world to have numerous fossils of animals and plants representing a whole series of time slices in the 1 million years following the Cretaceous–Paleogene, or K–Pg, extinction.

Over the last three years, a team led by researchers at the Denver Museum of Nature and Science has uncovered more than 7,000 fossils there. These include 233 kinds of plants and 16 species of mammals — among which are the earliest known mammals to reach relatively large sizes as they evolved and filled ecological roles previously occupied by dinosaurs (SN: 1/25/17).

Despite a century of searching, the site had previously yielded few fossils — until paleontologist Tyler Lyson realized in 2016 that bones were preserved inside nodules of rock called concretions, rather than visible among the surface rocks.

That eureka moment allowed his team to “crack the code” of discovery there, Lyson says. “That was the real game-changing moment when I broke open the first concretion and saw a mammal skull staring back at me.”

By comparing plant and animal fossils with data on precise dates, the researchers have puzzled together the story of what happened at Corral Bluffs 65 million to 66 million years ago. Following the global devastation wrought by the asteroid impact, ferns and palms dominated, but were slowly replaced by forests with a much greater diversity of trees.

Mammals took a little while to recover, but then swiftly diversified into a variety of forms and body sizes. The biggest initial survivors of the impact weighed just 500 grams, about the size of a rat. But in layers of rock dated to just 100,000 years later, raccoon-sized mammals weighing up to six kilograms appear, Lyson says, not too far off from the maximum size mammals had reached before the mass extinction.

A lack of large predators in the post-impact world — as well as an explosion in plant diversity, offering a wider variety of better food sources — may be what allowed some mammals to reach 25 to 30 kilograms, such as beaver-sized Carsioptychus, by 300,000 years after the impact.

By 700,000 years in the same rocks that the earliest known members of the legume, or bean, family of plants are found, mammals of nearly 50 kilograms appear, such as wolf-sized Eoconodon.

Aside from the sheer number of fossils and different time slices revealed at Corral Bluffs, it was the number of mammal skulls — at least 40 so far, Lyson says — that astounded Brusatte. Skulls are usually very rare and mammals from around this time are typically “known just from teeth, and maybe a few bones here and there,” he says.

Brusatte is working on a site in New Mexico that is one of very few others with similarly aged vertebrate fossils. Though those fossils are less complete, they also point to a rapid recovery and diversification of mammals after the impact. “Different areas are giving the same signal; that tells us that it’s probably true,” he says.

While many mammals before the impact were from long-extinct subgroups, placental mammals, the young of which develop in a womb, came to dominate afterward, making up 95 percent of the roughly 6,500 mammal species alive today. “This is the best record to my knowledge on Earth that shows the recovery of terrestrial biotas after the K–Pg extinction,” says Jin Meng, a paleontologist and expert on dinosaur-era mammals at the American Museum of Natural History in New York City. “The study shows at least part of the earliest record, part of the trunk, of the placental mammal tree of life.”

How bald eagles fly, new research


This 2017 video from the USA says about itself:

An American Bald Eagle flies with a GoPro

Jeep is a 5-year-old American Bald Eagle in Apopka, Florida. After losing a talon in 2012, Jeep (named after the “GP” in GoPro) is now rehabilitated and acting as an educational ambassador for the Avian Reconditioning Center in Apopka.

From the University of British Columbia in Canada:

Why are bald eagles such great gliders? It’s all in the wrist

New research helps explain how nature reshapes wings

October 24, 2019

Summary: Birds come in an astounding array of shapes and colors. New research helps explain why bird species with similar flight styles or body sizes don’t have consistent wing shapes. Bird species tend to reshape the range of motion of their wings — rather than wing shape or size itself — as they evolve new ways of flying.

Birds come in an astounding array of shapes and colours. But it’s their physical prowess — like a bald eagle’s incredible ability to soar — that captivates human imagination.

An enduring mystery is why bird species with similar flight styles or body sizes don’t have consistent wing shapes. All hummingbirds, and some species of falcons, hawks, kingfishers and passerines can hover, but the birds have strikingly different morphologies and are only distantly related. Ravens soar like eagles while their look-alike cousins, crows, stick more closely to the ground.

New research in Science Advances helps explain why. Bird species tend to reshape the range of motion of their wings — rather than wing shape or size itself — as they evolve new ways of flying.

“Birds essentially swim through the air — they flex, extend and bend their wings in flight,” explains Vikram Baliga, a researcher at the University of British Columbia and lead author on the paper. “As a bird specializes in a flight style, nature doesn’t appear to reshape the size or shape of the wing as much as it remodels the wing’s range of motion. Much like a swimmer adjusting their stroke.”

Hovering birds, according to the research, are relatively restricted in their ability to extend their elbows, but have a generous capability to move their wrist.

“Hummingbirds basically tuck their elbows in and predominately rely on rapidly swinging their wings at the wrist joint,” says Baliga. “For birds that glide, it’s more about maintaining the position of the limbs to keep steady sail. The most restricted species in our study are the bald eagle (Haliaeetus leucocepalus) and the sooty shearwater (Ardenna grisea), both of which frequently soar and glide.”

Baliga and UBC zoologists Douglas Altshuler and Ildiko Szabo categorized 61 species of birds by flight style — from hovering to gliding to soaring. Using samples collected by the UBC Beaty Biodiversity Museum, the researchers manually measured the shape, flexibility and extendibility of each species’ wing. They also built an evolutionary family tree of the birds to then determine how range of motion evolved in the wrists and elbows of bird’s wings.

This work provides insights for drone and aircraft design. Engineers are looking to nature, using bioinspiration to improve flying performance.

“By looking across avian flight diversity, our research has determined one component of how birds use their wings,” says Baliga. “We’re working towards understanding how wings in nature morph during flight so that the knowledge can be applied to unmanned aerial vehicles — particularly in turbulence, wind gusts, or when attacked by aerial predators.

“Evolution has tested a range of wing designs and motions for specific circumstances. Looking at the restrictions that nature places on birds of different sizes and flight styles can help us understand what does and does not work when designing new technology.”

Dutch government attacks press freedom, journalists protest


The Rotterdam, the Netherlands courthouse, ANP photo

Translated from Dutch NOS radio today:

Journalists demonstrate for release of NOS reporter

At 10:00 a demonstration for the release from jail of NOS [Dutch national TV and radio] journalist Robert Bas starts at the court in Rotterdam. Bas was jailed by a judge yesterday, because he doesn’t want to say anything about a conversation with one of his sources. As a result, he might endanger his source and himself, he says. Bas relies on his journalistic rights.

The demonstration is an initiative of NRC daily journalist Marcel Haenen. The journalists’ union NVJ and journalists from many other media support it.

Turkish situation

Haenen said in the NOS Radio 1 Journal that the government on the one hand says that freedom of news gathering and protection of resources is important, but at the same time they are spying on whistleblowers or suspending them.

As a result, sources are taking more and more precautionary measures to avoid difficulties. “That makes the work of the journalists increasingly difficult, certainly for investigative journalists,” says Haenen. “Then you would expect the judiciary to protect journalists and see that it is a democratic achievement that you have a free press. These are Turkish conditions, you should not want that.”

In addition, some journalists have to be protected 24 hours a day because criminal gangs are threatening them. “Then it is completely outrageous that a judge now decides that a journalist should be locked up because he does not want to give up his source. It is an ever-increasing violation of the freedom to gather news.”

Haenen also considers jailing a stupid measure for practical reasons. “It is an illusion to think that a journalist is inclined to talk if you put him behind bars. That will have no effect whatsoever.”