What Kinds Of Animals Survived The Dinosaur Extintion And How

Great Spotted Woodpecker — A great spotted woodpecker eats a hazelnut. Bird beaks may have allowed the animals to consume seeds and nuts afterward an asteroid hit the earth, wiping out many forms of life. Photo by: Arterra/Universal Images Group via Getty Images

Birds are the only dinosaurs left. That might seem strange. A pigeon or a penguin doesn't await much like a Tyrannosaurus. But the connection is still there, all the way downward to the bone. Nigh 150 million years ago, in the Jurassic, the first birds evolved from small, feathery, raptor-like dinosaurs, becoming another co-operative on the dinosaur family tree. For more than eighty one thousand thousand years, birds of all sorts flourished, from loon-like swimmers with teeth to beaked birds that carried streamer-similar feathers as they flew.

With retrospect, birds can exist categorized as avian dinosaurs and all the other sorts—from Stegosaurus to Brontosaurus—are non-avian dinosaurs. The entire reason paleontologists make that split up is because of a catastrophe that struck 66 meg years agone. An asteroid more 6 miles across struck what's now the Yucatan Peninsula, triggering the fifth mass extinction in the earth's history. Some of the droppings thrown into the atmosphere returned to Globe, the friction turning the air into an oven and sparking woods fires as it landed all over the earth. And so the intensity of the heat pulse gave way to a prolonged bear upon winter, the sky blotted out by soot and ash every bit temperatures fell. All told, more than 75 percent of species known from the stop of the Cretaceous period, 66 one thousand thousand years ago, didn't make it to the following Paleogene menstruum. The geologic break betwixt the 2 is chosen the K-Pg boundary, and beaked birds were the simply dinosaurs to survive the disaster.

"In that location has been a lot of discussion about what enabled modern-blazon birds to survive the K-Pg extinction while other birds groups, non-avian dinosaurs, and even pterosaurs perished," says Regal BC Museum paleontologist Derek Larson. The end of the Cretaceous boasted an entire array of birds and bird-like reptiles. Just of these groups, information technology was merely the beaked birds that survived. The happenstances of evolution had given birds a lucky suspension, the fundamental events set in move long before the asteroid struck.

All living birds have toothless beaks, only this wasn't always so. The very first bird, the 150 million-year-old Archaeopteryx, initially confounded 19th century naturalists because information technology had teeth. For tens of millions of years after Archaeopteryx, toothed birds continued to thrive and evolve alongside their dinosaurian relatives. And some of these toothed birds eventually lost their teeth, plucking up their meals with toothless beaks instead.

The question is what evolutionary pressures pushed birds to lose teeth when teeth seem and so useful. Given that most birds fly, adaptation to the air seemed similar a possibility. "Older hypotheses focused on the idea of weight reduction for flight," says University of Texas at Austin paleontologist Grace Musser, but the discovery that some toothed birds were strong fliers has led researchers back to the drawing board.

Rather than flight, nutrient might have given birds an evolutionary nudge towards toothless beaks every bit aboriginal avians thrived among other dinosaurs. Paleontologists accept noticed that some dinosaur groups, including birds, evolved beaks and lost teeth every bit they became more herbivorous. While the earliest birds had teeth to nab insects and other minor morsels, some bird lineages started to specialize on fruit, seeds, and other establish foods. Instead of teeth to catch, the birds evolved beaks to pluck and pick.

Among the birds that began to lose teeth in favor of beaks, the mode beaks form during development may have helped the evolutionary shift. "Changes to the skull and face every bit the beak became more than circuitous may have moved developing tissues effectually, changing how they interact in the embryo, and resulted in the loss of molar formation," says King's Higher London anatomist Abigail Tucker.

"All the things that make birds, birds, were already in place well before the mass extinction," says University Higher London anatomist Ryan Felice.

When the extinction struck, the traits birds had been evolving for millions of years fabricated the difference between life and death. While some birds survived the affect and its backwash, not all of them did. "When nosotros think about hypotheses of traits that let birds survive, nosotros need to take into account that it was only a small sliver of diversity that fabricated information technology to the other side," Felice says. Entire groups of birds, such as toothed birds called enantiornithes, went extinct. It's unlikely that 1 single trait determined the fate of all these species. Still, surviving extinction oftentimes comes down to luck, and beaks may have been some birds' ace.

Past the stop of the Cretaceous, beaked birds were already eating a much more varied diet than their toothed relatives. These birds weren't specialized on insects or other animal food, and so they were able to pluck upwards difficult food items like seeds and nuts. And in the backwash of the extinction, when animal life was severely cut back, those hard, persistent petty morsels got beaked birds through the hard times. Beaked birds were able to feed on the seeds of the destroyed forests and await out the decades until vegetation began to return.

Non that beaks guaranteed survival of the impact event. The duck-like bird Vegavis lived at the end of the Cretaceous and had a neb, yet there's no indication that this avian survived. "Only having a beak was not enough," Tucker says. Rather, it's that birds with beaks and powerful gizzards capable of crushing tough seeds had an unexpected advantage that increased their chances of survival.

Both fossils and the timeline of bird evolution discerned from their genetic relationships indicates that early members of modernistic bird groups—such as birds related to ducks, parrots, and chickens—were around by time the asteroid struck. These groups nevertheless suffered losses, but enough survived to set up a new pulse of bird development in the millions of years following the catastrophe. Many bird lineages became smaller in size while maintaining their encephalon size. Through evolutionary shrinking, birds wound up with larger brains compared to their trunk size, setting the stage for avian intelligence beyond what the non-avian dinosaurs could have evolved.

But big evolutionary changes often come with constraints. "The loss of teeth does limit the number of dietary niches birds could explore," Felice says. "Herbivorous mammals and non-avian dinosaurs evolved ever-growing teeth and then that could continue eating as the plants wore their teeth down, simply this just isn't possible with a bill," Felice says. And that ways that bird skulls haven't needed to vary as much to support different jaws and ways of feeding, meaning that birds look like evolutionary slowpokes compared to non-avian dinosaurs—every bit Felice and colleagues constitute in a new study of bird skull evolution.

To empathize more than about how birds managed to survive and make a living in a world recovering from 1 of the worst mass extinctions of all fourth dimension, the task at hand is to observe more fossils from the time directly post-obit the mass extinction, from a time called the Paleocene. Paleontologists have some cracking examples of fossil birds from about 10 meg years after the disaster, from a fourth dimension chosen the Eocene, only birds fossils from the slice in betwixt the Cretaceous and Eocene are fragmentary and hard to observe. These are the bones that may reveal new secrets.

Source: https://www.smithsonianmag.com/science-nature/why-birds-survived-and-dinosaurs-went-extinct-after-asteroid-hit-earth-180975801/

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