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Let’s begin with a definition: Dinosaurs, in keeping with the Pure Historical past Museum in London, have been the dominant group of animals that roamed the land for between 140 and 160 million years.

Sure, all dinosaurs have been egg-laying reptiles. However they have been additionally distinct from different reptiles that lived across the identical time.

For one, that they had straight hind legs that stood perpendicular to their our bodies. These helped them to make use of much less vitality in contrast with different reptiles – similar to crocodiles, which have a sprawling gait.

Dinosaurs additionally had two holes behind their eye sockets, by means of which sturdy muscle tissues have been threaded. As a result of these muscle tissues related the jaw with the cranium, they allowed for a extra forceful chunk.

It might appear that their categorization as reptiles is probably a bit overly simplistic. The extra sophisticated reply hinges on how precisely we outline what a reptile is. And to reply that query, we should revisit the dinosaurs’ downfall.

Learn Extra: How the Age of Reptiles Started 250 Million Years In the past

When Did Dinos Go Extinct?

Most dinosaur species met their finish throughout a mass extinction occasion that additionally killed roughly 75 p.c of the planet’s complete plant and animal species.

What precisely prompted the mass extinction stays considerably open to debate, says Abdulrahman Bamerni, a geologist and lecturer on the College of Duhok in Iraq. He research the composition of rock layers to raised perceive what finally led to the creatures’ demise.

Theories have ranged from the credible, similar to international warming and volcanic eruptions, to the downright weird – similar to dinosaurs growing a style for their very own eggs, or there being not sufficient feminine dinosaurs to adequately repopulate.

One 2019 paper revealed within the Journal of Dietary Science even explored whether or not vitamin D shortages could possibly be responsible. Such a deficiency might have lowered the integrity of their eggs, leaving most lifeless earlier than they have been even born.

Specialists now largely agree, nevertheless, {that a} meteorite collision was concerned to some extent. Its affect probably set into movement a sequence of earthquakes around the globe, kicking up big quantities of particles and mud into the ambiance.

This particulate matter would have restricted daylight and lowered the capability of crops to photosynthesize — the results of which ultimately reverberated all the best way up the meals chain, to predators similar to dinosaurs.

Is a Chicken a Reptile?

Not all life was extinguished, nevertheless. Feathered dinosaurs, which later advanced into modern-day birds, managed to outlive.

Birds are, actually, the one direct descendants of dinosaurs. (Crocodiles and alligators come from a standard ancestor that predates the looks of dinosaurs.) Some specialists even make the case that birds nonetheless are dinosaurs.

That assertion has led to a debate over whether or not there’s a significant distinction between birds and reptiles. Are birds, because the heirs of Tyrannosaurus Rex, only a sub-type of reptiles?

To unravel this, it’s essential to know that there are two important techniques that biologists use to categorise animals: the Linnean system, which dates from the 1730s, and phylogenetics, which first happened within the Nineteen Forties.

Learn Extra: What Species As we speak Are Descendants of Dinosaurs?

What Is a Reptile?

The Linnean method of sorting depends on an animal’s bodily traits and largely ignores their ancestry. If we’re utilizing the Linnean system, we should admit {that a} reptile is a cold-blooded animal with scales — and due to this fact birds aren’t reptiles.

And if we settle for that definition, then we should additionally settle for that the feathered dinosaurs that later advanced into birds have been additionally not reptiles. Due to this fact, that signifies that not all dinosaurs have been reptiles, proper?

Phylogenetics is probably a little bit extra subtle. This cataloguing approach makes use of bodily attributes to research an animal’s evolutionary historical past after which group them by their shared ancestors.

Had been All Dinosaurs Reptiles?

On this case, that might imply any descendant of a reptile can be a reptile. And with that definition, it’s simpler to argue that birds are actually reptiles — and that every one dinosaurs have been reptiles too, in keeping with the College of Michigan.

The Linnean system helps us to grasp how animals dwell, what ecological area of interest they occupy and the way they work together with their atmosphere. However, the phylogenetic method helps us obtain a way of how animals got here to be.

Each strategies have their makes use of, so be at liberty to argue that every one dinosaurs have been reptiles — or weren’t reptiles — to your coronary heart’s content material.

Learn Extra: How Do Scientists Reconstruct What Dinosaurs Seemed Like?