how dinosaurs shrank and became birds

Huge meat-eating dinosaurs shrank steadily over 50 million years to evolve into small, flying birds, researchers say.

The branch of theropod dinosaurs which gave rise to modern birds decreased inexorably in size from 163kg beasts that roamed the land, to birds weighing less than 1kg over the period.

The radical transformation began around 200m years ago and was likely driven by a move to the trees where creatures with smaller, lighter bodies and other features, such as large eyes for 3D vision, fared better than others.

Scientists pieced together the dinosaurs sustained shrinkage after analysing more than 1,500 anatomical features of 120 species of theropods and early birds.

The evolutionary tree reveals that the theropod ancestors of modern birds underwent 12 substantial decreases in size that led to archaeopteryx, the earliest known bird on Earth. The rate at which they evolved distinct features, such as feathers, wings and wishbones, was four times faster than adaptations in other dinosaurs.

“Birds evolved through a unique phase of sustained miniaturisation in dinosaurs,” said Michael Lee at the University of Adelaide. “Being smaller and lighter in the land of giants, with rapidly evolving anatomical adaptations, provided these bird ancestors with new ecological opportunities, such as the ability to climb trees, glide and fly. Ultimately, this evolutionary flexibility helped birds survive the deadly meteorite impact which killed off all their dinosaurian cousins,” he added. The study is published in the journal, Science.

The steady reduction in size saw the two-legged land-based theropods evolve new bird-like features, including shorter snouts, smaller teeth and insulating feathers.

Gareth Dyke, a vertebrate palaeontologist and co-author of the study at Southampton University said: “The dinosaurs most closely related to birds are all small, and many of them, such as the aptly named Microraptor, had some ability to climb and glide.”

In an accompanying article, Michael Benton at Bristol University, said that the long-term trend that led to modern birds was probably shaped by the animals taking up in new habitats. “The crucial driver may have been a move to the trees, perhaps to escape from predation or to exploit new food resources,” he writes.

A smaller body size would have benefited animals living in the trees, while enlarged eyes would improve their 3D vision to avoid collisions with branches. Insulating feathers could have helped them hunt at night, and elongated forelimbs gave them increasingly more impressive wings to enable more daring leaps from tree to tree, Benton writes.

In an accompanying article, Michael Benton at Bristol University, said that the long-term trend that led to modern birds was probably shaped by the animals taking up in new habitats. “The crucial driver may have been a move to the trees, perhaps to escape from predation or to exploit new food resources,” he writes.

The evolutionary tree shows that the earliest known bird on Earth, archaeopteryx, descended from the theropod ancestors of modern birds, who underwent twelve significant size reductions. Their unique characteristics, like wings, feathers, and wishbones, evolved four times more quickly than those of other dinosaurs.

Over the course of time, the 163 kg beasts that once roamed the land gave way to birds weighing less than 1 kg, a gradual decline in size from the theropod dinosaur branch that gave rise to modern birds.

Researchers assembled the shrinkage that the dinosaurs experienced by examining over 1,500 anatomical characteristics from 120 theropod and early bird species.

The study’s co-author, Southampton University vertebrate palaeontologist Gareth Dyke, stated: “The dinosaurs most closely related to birds are all small, and many of them, like the aptly named Microraptor, had some ability to climb and glide.” “.

They discovered that there were two activity patches in mammals and reptiles, one on each side of the growing nasal cavity. In contrast, birds had a single, much larger patch across their entire face. Because alligators and dinosaurs share similar snouts and premaxillary bones, the researchers reasoned that the alligator pattern could be used as a stand-in for the dinosaur pattern. The scientists then used chemicals to block the genes in the middle of the face, undoing a bird-specific pattern of gene expression in chicken embryos. (They refrained from letting the chickens hatch out of ethical concerns.) ).

But as soon as those avian characteristics appeared, birds took off. According to Brusatte’s research on coelurosaurs, the evolution of archaeopteryx and other extinct birds started considerably faster than that of other dinosaurs. The optimistic monster theory had it almost exactly backwards: birds weren’t produced by a burst of evolution. Rather, birds produced a burst of evolution. “It appears that birds discovered a highly effective new body plan and new kind of ecology—flying at small sizes—and this resulted in an explosion of evolutionary change,” Brusatte stated.

Theropods, a group of two-legged dinosaurs that included the massive Tyrannosaurus rex and the smaller velociraptors, are the ancestors of modern birds. The most closely related theropods to modern birds weighed between 100 and 500 pounds on average, making them giants in comparison. They also had large snouts, large teeth, and little space between their ears. For instance, a velociraptor’s brain was about the size of a pigeon’s, while its skull resembled that of a coyote.

Two bones called the premaxillary bones combine to form the beak in modern birds. That structure is very different from the majority of other vertebrates, dinosaurs, alligators, and extinct birds, where these two bones stay apart and shape the snout. Researchers mapped the expression of two genes found in these bones in a variety of animals, including alligators, chickens, mice, lizards, turtles, and emus, a living species that resembles prehistoric birds, to determine how that change might have developed.

(In fact, paedomorphosis may have contributed to several significant evolutionary transitions, including the emergence of mammals and humans. Our large skulls in comparison to chimpanzees may be the result of paedomorphosis. Moreover, paedomorphosis contributed to the skull’s transformation into a blank canvas, allowing selection to forge new structural patterns. It may have cleared the way for the development of the beak, another crucial characteristic of birds, by eliminating the snout.

FAQ

How did the dinosaurs evolve into birds?

And recent research suggests that a few simple change—among them the adoption of a more babylike skull shape into adulthood—likely played essential roles in the final push to bird-hood. Not only are birds much smaller than their dinosaur ancestors, they closely resemble dinosaur embryos.

How long did it take for dinosaurs to turn into birds?

It took 50 million years of continual shrinking to turn massive, lumbering dinosaurs into the first small flying birds.

How did dinosaurs become smaller?

Evolution Required Change Therefore, the primary reason dinosaurs shrank and became birds is because it gave them more opportunities for survival. Theropods had to shrink over millennia, meaning their two legs, snouts, and teeth became shorter.

Did chickens evolve from dinosaurs?

It turns out that one species of maniraptoran dinosaurs was the ancestor of all birds, including chickens. That lineage branched off in the Creataceous and by 65 million years ago there were at least 3 Orders of birds.