MODERN DAY DINOSAURS
- Ayushi Mishra
- May 1, 2023
- 5 min read
Updated: May 4, 2023
“Dinosaurs are NOT extinct” say, and believe, all the paleontologists in the world. In fact, over ten thousand species of dinosaurs are alive and kicking today.
We are so used to saying that dinosaurs are extinct that we don’t even realize how close birds (dinosaurs of today) are to the dinosaurs of the past. Sure, you might have had the closest living relative of T. Rex for dinner (the chicken), but that doesn’t give us a right to denigrate them.
Birds evolved from dinosaurs, and that makes them dinosaurs. They are no less of a dinosaurian than, say, a T. rex. No group of animals, living or dead, share a degree of commonality as strongly as birds and theropods do. Just because all ancestors died, doesn't mean we can neglect their presence and call the evolved species’ branch a whole new clade. It's a cut from the same cloth.
Here is a little dinosaur overview to make our understanding more clear as to HOW A DINOSAUR BECAME A BIRD.
Theropoda IS a dinosaur clade “characterised by hollow bones and three toes and claws on each limb.” Basically, they are the dinosaurs that looked somewhat like this:
In contrast, sauropods were dinosaurs that looked like this, massive and herbivore.
The theropod lineage extends till modern day birds.
“THE REALISATION THAT birds are dinosaurs is probably the single most important fact ever discovered by dinosaur palaeontologists. ”
First Evidence
The first evidence comes from a Jurassic hybrid Archaeopteryx - the oldest bird in the fossil record. Archaeopteryx is the oldest dinosaur we know to possess “birdly” features. It had a wishbone, like a bird but its jaws were lined with sharp teeth, like a reptile.
Back in the 1920s, an argument was made that birds couldn’t have come from dinosaurs because dinosaurs apparently didn’t have collarbones (which birds fuse into wishbones). This viewpoint was held till the 1960s. Today we realize that dinosaurs did have collarbones.
Wishbones aside, scientists who believed that birds were in fact dinosaurs, needed to prove one thing that's quintessentially “bird”: feathers. Many dinosaurs like Velociraptor or Deinonychus were discovered later by scientists like John Harold Ostromom; but all that was available to observe were birdyl bones. No soft parts like feathers to prove their point.
Second Evidence
Phil Currie during the 1980s and the 1990s finally discovered the first dinosaur fossil preserved with feathers. These fossils were discovered in the Liaoning region of China. Twenty such species are known now.
Feathers have so many uses that it has been difficult to figure out which purpose they first evolved to serve and how they were modified into airfoils.
Liaoning fossils of species like Psittacosaurus—are found coated in some type of integument. The material that glazed their body was more like fluff, made up of thousands of hairlike filaments that palaeontologists call proto-feathers. So the first feathers must have evolved for something else, like to keep these small dinosaurs warm or maybe as a way to camouflage their bodies.
OTHER EVIDENCES
The features that allow us to immediately recognize a bird as a bird are not actually trademarks of birds. They’re attributes of dinosaurs.
As birds descended from dinosaurs and the fossilized feathers of the half-bird, half-dinosaur Archaeopteryx were later discovered, it is reasonable to assume that feathers originated somewhere along the evolutionary tree before birds came into picture. Feathers developed much earlier, in ground-living theropods, for reasons wholly unrelated to flight.
Long, straight legs and feet with three skinny main toes—hallmarks of the modern bird silhouette— first appeared more than 230 million years ago in the most primitive dinosaurs, as their bodies were reshaped into upright-walking, fast-running engines.
Some upright-walking dinosaurs—the earliest members of the theropod dynasty—fused their left and right collar bones into a new structure, the wishbone. This seemingly minor change stabilized the shoulder girdle and probably allowed these predators to better absorb the shock forces of grabbing prey. Later, birds would co-opt the wishbone to serve as a spring that stores energy when they flap their wings, just as the inventor of the propeller had no idea the Wright Brothers would later put it on an airplane.
Later, a subset of these small, upright, wishboned theropods started to fold their arms against the body, probably to protect the delicate quill- pen feathers that were evolving around the same time.
Not only anatomically, most notable behaviours and biological characteristics of living birds also have deep dinosaurian heritage.
Numerous theropods, found in the Gobi and elsewhere, had bones hollowed out by air sacs, which, are signs that they had the ultra-efficient “flow through” lung that takes in oxygen during both inhalation and exhalation, a precious feature of birds to maintain their high-energy way of life.
The microscopic structure of dinosaur bones indicates that many species—including all known theropods—had growth rates and physiologies intermediate between slow maturing, cold-blooded reptiles and the fast-growing, warm-blooded birds of today. Thus, a flow-through lung and relatively fast growth emerged more than 100 million years before birds took wing.
Both the typical sleeping posture of birds and the way in which they mine calcium from their bones for the shells of their eggs first arose in dinosaurs long before birds.
Later in North America, some dinosaur fossils had wings but also hefty bodies, pathetically undersized wings, and puny frames made them wholly unsuitable for the air. But why else would a dinosaur develop wings?
Today’s birds use their wings for many things other than flying (which is why, for instance, flightless birds like ostriches don’t lose their arms entirely).
Also used as display structures to entice mates and frighten rivals, as stabilizers that help birds climb, as fins to help them swim, and as blankets for keeping eggs warm in the nest, along with many other functions.
Wings could have evolved for any of these reasons—but display seems the most likely, and there is growing evidence for it.
Flight probably evolved many times in parallel, as different species of these dinosaurs—with their different airfoil and feather arrangements—found themselves generating lift from their wings as they leaped from the ground, scurried up trees, or jumped between branches. Yi qi—maybe the wackiest dinosaur ever found— had a wing, but not made of feathers. Instead, it had a membrane of skin stretching between its fingers and body, like a bat.
That Microraptor and Yi have such divergent wing configurations, is some of the strongest evidence that different dinosaurs were evolving distinct flight styles independently of one another.
The descendants of Microraptor or Anchiornis, evolved completely separately—got even smaller, developed bigger chest muscles and hyper elongated arms, lost their tails and teeth, ditched one of their ovaries, and hollowed out their bones even more to lessen their weight. Breathing became more efficient, their growth faster, and their metabolism more supercharged, so that they became fully warm, able to maintain a constant high internal body temperature. With each evolutionary enhancement, they became even better fliers. These were the dinosaurs that became the birds of today.
The first birds were evolving much faster than their dinosaur ancestors and cousins, and they maintained these accelerated rates for many tens of millions of years. It had taken tens of millions of years for evolution to make a flying bird out of a dinosaur. Many birds lived during the Age of Dinosaurs. The first flapping fliers must have originated sometime before 150 million years ago, because that is the age of Archaeopteryx.
EVOLUTION MADE BIRDS from dinosaurs. Velociraptor, Deinonychus, and Zhenyuanlong are on that “non-bird” side of the genealogy, but were they around today, we would probably consider them just another type of bird, no stranger than a turkey or an ostrich.
Book: The Rise and Fall of the Dinosaurs: A New History of a Lost World By Steve Brusatte
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