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How Do We Know Birds Are Dinosaurs?

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Illustration: Benjamin Currie

Fierce tyrannosaurs and important sauropods are gone, but dinosaurs continue to joke among us. We are talking about birds, of course, but it is not completely obvious why we should consider that birds are good faith dinos. Here are the many reasons why.

Make no mistake, birds are legitimate dinosaurs, and not some evolutionary branch. All non-avian dinosaurs were wiped out after asteroid-induced mass extinction 66 million years ago, but some bird species – probably birds that live on land-Manigated to survive, and them he wasted no time to recover once his parents were gone.

“Those little ones singing outside your window are the dinosaurs we’ve abandoned these days,” Adam Smith, curator of Clemson University’s Campbell Geology Museum, explains in an email. “Birds are just one type of dinosaur.” To say “birds descend from dinosaurs” is similar to saying that people descend from mammals. In short, all birds are dinosaurs, but not all dinosaurs are birds. “

This warbler doesn’t mind being called a dinosaur.

This warbler doesn’t mind being called a dinosaur.
Image: US Fish and Wildlife Service

That birds are somehow connected to dinosaurs is hardly a recent revelation. In the late 19th century, English naturalist Thomas Henry Huxley completely suggested that birds evolved from dinosaurs. As science writer Riley Black he wrote in 2010, his ideas about the origin of birds “were not a perfect anticipation of our current knowledge,” but Huxley, a skilled anatomist, was clearly on to something.

In fact, scientists have identified a number of features that comfortably position themselves as birds like dinosaurs in the phylogenetic tree. Kate Lyons, an assistant professor at Lincoln School of Biological Sciences at the University of Nebraska, says “it’s not just a smoking gun” that allows paleontologists to say that birds are dinosaurs, since they are there. ” several proofs ”indicating this conclusion, as she wrote me in an email.

Paleontologist Steven Brussatte of the University of Edinburgh says we know that birds are dinosaurs applying the same reasoning that bats are mammals.

Look at this dinosaur.  Specifically, a brown booby.

Look at this dinosaur. Specifically, a brown booby.
Image: NOAA / NMFS / OPR

“Yeah, the birds are small, they have feathers, wings, and they fly, and that’s different from the images of dinosaurs we’re used to,” he wrote in an email. “Bats are the analogy of mammals – they’re small, they have wings and they fly, and they don’t look anything like a dog, an elephant or a primate, but they’re still mammals.”

In fact, bats present many unique traits to mammals, such as hair, molar teeth, three small ear bones, and the ability to feed children with milk. Similarly, birds have characteristics that are only seen in theropod dinosaurs, explains Brussatte.

Like feathers.

In fact, while there isn’t a “smoking gun” to hit birds like dinosaurs, the presence of feathers is probably the coolest thing of all. The fossil record is full of examples of feathered dinosaurs they did not have, and because the feathers are unique to birds, scientists are able to link the two as dinosaurs.

Skeptics may argue that the emergence of feathers in both birds and non-avian dinosaurs is a consequence of convergent evolution, in which similar traits appeared independent in non-parent species Smith says convergent evolution is unlikely in this case because “many of the non-avian dinosaurs that were found with preserved feathers are the exact species that were already there, independently hypothesized to be close relatives of birds, ”he said Velociraptors and Sinosauropteryx.

Artist's interpretation of Velociraptor mongoliensis.

Artist ‘s interpretation of Velociraptor mongoliensis.
Illustration: Fred Wierum (Use Right)

He added: “Feathers are ridiculously complex structures, and while convergent evolution often gives results in similar structures – and even healthy animals – that appear on the surface to be quite similar, there are no examples of convergent evolution that doubles. structures on that scale, with that sort of fidelity. ”

Phylogenetics – the study of evolutionary relationships between species – provides other evidence that birds are dinosaurs, as Andre Rowe, a doctoral student from the School of Earth Sciences at the University of Bristol, explained in an email. With all due respect to Jurassic Park, Paleontologists are not able to extract and analyze ancient dinosaur DNA, but they can examine key features shared between species as indicated by their skeletons and anatomy. Based on these key features, scientists “can say with almost certainty that birds belong to the lineage of theropod dinosaurs,” Rowe said, referring to meat-eating dinosaurs such as T. rex, Allosaurus, and Compsognathus. Importantly, theropod and bird skeletons show “not abrupt changes in their evolutionary relationship, but rather a smooth transition over millions of years,” he added.

“By taking a trip back in time, we can trace the evolution of the bird’s body’s ground plan to some of the first dinosaurs,” wrote Kristi Curry Rogers, a vertebrate paleontologist at Macalester College in Minnesota. , in an email. “Like dinosaurs, birds walk with their paws held directly under their bodies, and dinos give birds a little more in growth rates.”

All birds are dinosaurs, but not all dinosaurs are birds.  Here, a Tyrannosaurus skeleton is mounted next to a Triceratops skeleton at the Los Angeles Museum of Natural History.

All birds are dinosaurs, but not all dinosaurs are birds. Here, a Tyrannosaurus skeleton is mounted next to a Triceratops skeleton at the Los Angeles Museum of Natural History.
Image: Matthew Dillon (Use Right)

Holly Woodward Ballard, an associate professor of paleontology and anatomy at the University of Oklahoma, says, “We know that birds are dinosaurs because they have more in common with extinct dinosaurs than other groups of living animals.”

In fact, there are several other features to consider – things like “desired bones, bones dug from air pockets, and wrists that can rotate,” allowing dinosaurs to “fold their arms against the body. “, according to Brussatte.

In an email, paleontologist and evolutionary biologist Jessica Theodor of the University of Calgary described these and other specific features of dino. For example, the structure that allows birds to fold their hands behind their wrists, which they do to bend their wings, is also found in the wingless arms. celurosaurs, and biologists can trace the modification of this structure “through the evolution of theropods,” he explained.

Compare between Majungasaurus air sacs and a duck.

Compare between Majungasaurus air sacs and a duck.
Graph: Zina Deretsky / NSF

Kat Schroeder, a doctoral student in the Department of Biology at the University of New Mexico, described the fusion of certain vertebrae in the synsacrum and pygostyle as one of the most significant evolutionary adaptations in birds.

“The synsacrum is the fusion of the vertebrae on the hips, which strengthens the shoulders and helps with flight, and the pygostyle is a fusion of the last caudal vertebrae that support the tail feathers, which is actually found in some dinosaurs had no like Oviraptorosaurs and Ornithomimosaurs which may have feather fans instead of long tails or fans at the tip of the tail, ”he wrote in an email.

“Birds have small flanges on their ribs, called hooked processes, that provide some mechanical advantage to the respiratory muscles of the rib cage,” and are also found in oviraptors and dromaeosaurs, as Theodor explained. In addition, “bird skeletons have many other structural similarities with dinosaurs in the skeleton, which all put together in phylogenetic analysis,” he said.

Try to cave among some dinosaurs, where animals rest on their nests to keep their eggs warm and protected, is a behavior seen in modern birds, as Rowe reminded me. In addition, dinosaurs and birds used both cane stones (stones that are ingested to aid digestion), “since the stones would have crushed food that was already ingested,” he said.

As I said before, scientists cannot study ancient dinosaur DNA, but they can study modern dinosaur DNA.

“Evidence that birds are really just small dinosaurs that have learned to fly comes from fossil records of dinosaurs and also from the bodies and genomes of living birds,” explains Curry Rogers. “When we look at modern birds, we can see small memories of their fiercest history locked into the depths of their genes – extensive development programs to build longer tails and teeth.”

She added: “It’s okay – written in the bones and bodies of dinosaurs, alive and extinct!”

So the next time a hummingbird comes to your feeder, feel free to greet the little bird like a visiting dinosaur. You can also say that you tasted dinosaurs after eating some chicken wings, or that you were attacked by a dinosaur when a goose scared you away from its nest. And when the Toronto Blue Jays face off against the Baltimore Orioles, you’re good to refer to the matchup as the battle of the dinos.

It sounds strange, but you have the science to support you.

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