No other animals from the deep past capture our imaginations like dinosaurs.

Any kid old enough to hold a crayon can probably draw one.

And we older kids have our own images that come to mind when we think of the terrible lizards.

But the reason that we have to imagine the non-avian dinosaurs, of course, is that they're extinct.

Thankfully, a ton of science has gone into our understanding of how dinosaurs looked, and acted.

But the truth is, we've only had a few hundred years to bring that picture into focus.

So if you page through a book about natural history, or stroll through a museum hall, you'll get some idea of what paleontologists think dinosaurs looked like.

But even the most up-to-date restorations of our prehistoric favorites are only part of the story.

Because our image of dinosaurs has been constantly changing -- evolving, you might say -- ever since naturalists started studying them about 350 years ago.

And this evolution is reflected in hundreds of years' worth of drawings, paintings, and models of dinosaurs, each made in an attempt to get us a little closer to visualizing animals that have been lost to time.

Taken together, these pictures can tell us a whole lot about just how much we've learned in just a short three and a half centuries.

So today, we're going to explore the history of dinosaur science, as seen through the history of dinosaur art.

When naturalists first started to find dinosaur bones, they didn't quite know what to make of them ... as you can tell from the very first illustration of a dino fossil ever published.

Back in 1677 -- more than 160 years before the word "dinosaur" was even coined -- an English chemist named Robert Plot published his Natural History of Oxfordshire, a catalog of rocks, minerals and fossils from his home county.

And it included a drawing of a strange bone that had been found in a limestone quarry.

Plot could tell that it was the end of a femur, or a thigh bone.

But it was clearly from an animal far larger than any living in England at that time.

He suggested that the thigh fragment might have belonged to a Roman war elephant, or maybe even a giant human.

But it turned out that, in his book, Plot had given the world the very first scientific illustration of a dinosaur fossil.

In 1763, English naturalist Richard Brookes re-printed Plot's illustration, in a six-volume set he called A System of Natural History.

And Brookes bestowed a name on the fossil.

In a caption of Plot's picture, he called the specimen Scrotum humanum.

Because...really?

Because although he knew it was a piece of a femur, he thought it looked like ... a pair of human testicles.

Paleontologists now know that bone belonged to Megalosaurus, a dinosaur named by WIlliam Buckland in 1824.

Working from some more and better material - - including a lower jaw and teeth -- Buckland was able to tell that this animal was a previously-unknown kind of carnivorous reptile.

To Buckland's mind, the creature looked not like a giant, or an even elephant, but like a crocodile -- although, one about the size of a bus.

And from this time we still have a lithograph of the crucial fossil -- the one that established Megalosaurus as a new, fierce form of ancient life.

From these rather inauspicious beginnings - - cases of mistaken identity involving war elephants and human genitals -- the idea started to sink in that dinosaurs were something truly special -- specifically, a kind of reptile that used to exist, but didn't any more.

But, in the early 1800s, scientists still pictured dinosaurs as being much like the modern reptiles they knew.

The English physician Gideon Mantell, for example, figured that if dinosaurs were reptiles, then they must've basically been just giant lizards.

Based on some fossil teeth that he found in Sussex, Mantell was convinced that he had found the prehistoric equivalent of an iguana - - albeit one about 30 meters long.

He made a sketch of the creature's skeleton in his personal notes, following the same skeletal plan of the modern lizard.

And in 1825 he officially gave the animal the name Iguanodon, or "iguana tooth."

A few years later, Mantell was visited by artist John Martin.

Martin was famous for his paintings of dramatic, apocalyptic scenes, like his 1822 painting, The Destruction of Pompeii.

And after meeting Mantell, Martin used his vision of the Iguanodon to create the first - - and maybe the most over-the-top -- scene of dinosaur combat ever committed to canvas.

This painting, The Country of the Iguanodon is all coils and teeth and claws.

It's all very... Rawr.

And at the time, it summed up what experts thought ancient reptiles were like: Giant, vicious lizards who hissed and snapped at each other.

But all that was about to change.

British anatomist Richard Owen proposed that Megalosaurus, Iguanodon, and another newly discovered animal, called Hylaeosaurus, all shared special physical traits -- found in their hips and other bones -- that made them different from all other reptiles.

And in 1842, he came up with a new name for this form of extinct life: "dinosaur," from the Greek for "terrible lizard."

But Owen went even further than that.

Dinosaurs weren't just supersized lizards, he said.

In many ways, they resembled mammals in their structure and their stance.

And Owen portrayed his vision of dinosaurs not on paper, or canvas, but in three dimensions!

For England's Great Exhibition of 1854, Owen worked with artist Benjamin Waterhouse Hawkins to create life-sized versions of dinosaurs and other ancient creatures, as he pictured them.

The models were so immense that Hawkins even famously held a New Years' banquet inside a model of Iguanodon!

And when the models were unveiled to the public, they became the new image of what we thought dinosaurs looked like.

These animals were built more like rhinos, carrying their legs under their bodies, but with scaly skin and tails that dragged on the ground behind them.

And it was other new insights into dinosaurs' legs that led to the next big shift in how we imagined the animals.

Most of the earliest dinosaur fossils were found in Europe and were extremely fragmented.

Sometimes it was hard to tell which parts went with which.

But when naturalists started looking in North America, they found more complete skeletons that made paleontologists completely re-think dinosaurs.

A pair of critical finds were made in New Jersey.

In 1858, a farmer found the bones of an animal we now call Hadrosaurus.

The skeleton wasn't complete, but there were enough parts of the arms, legs, and tail to know that the forelimbs of this dinosaur were shorter than the hindlimbs.

Benjamin Waterhouse Hawkins was called in again to reconstruct the dinosaur's skeleton for the public in Philadelphia, the first one to be put on display anywhere.

And what was weird about this model was that ... it stood on two legs!

The discovery of a carnivorous dinosaur also in New Jersey, eventually named Dryptosaurus, showed that it was bipedal, too.

And its discoverer, the notoriously cranky American paleontologist Edward Drinker Cope, drew the dinosaur in a crouched, kangaroo-like pose, totally different from Owen's Megalosaurus.

Better finds only added fuel to this revolution in how we pictured dinosaurs.

The discovery of a whole herd of Iguanodon in a Belgian coal mine in 1878, including complete skeletons, confirmed that those dinosaurs had short arms and long legs, suggesting that they were also largely bipedal And the discovery of entirely new genera, like Stegosaurus, Brontosaurus, and Triceratops, showed that dinosaurs were stranger and more diverse than anything paleontologists expected.

Bone by bone and skeleton by skeleton, a new image of dinosaurs started to take hold.

Even though they were still classified as reptiles, by late 19th century, they were seen as acting more like mammals or birds than like lizards.

An important painting from 1896 drives this point home.

Charles R. Knight, working for the American Museum of Natural History, illustrated a moment of vicious combat between two snarling Dryptosaurus.

These weren't Martin's dragon-like lizards, or Owen's rhino-like reptiles.

Instead, they were agile, bird-like dinosaurs unlike anything we'd seen before.

Then, at the start of the 20th century, the scientific opinion on dinosaurs shifted yet again.

By this point, dinosaurs were seen as big and weird and scary -- great for drawing museum crowds!

-- but their reputation was starting to tarnish.

If dinosaurs were so great, some paleontologists wondered, then why'd they go extinct?

Instead of being awe-inspiring, dinos came to be seen as inferior, an evolutionary failure.

And this attitude was reflected in the paleo-art of the time, which depicted dinosaurs as slow, lumbering beasts -- usually stuck in some swamp.

Don't get me wrong, the artists of this time depicted these scenes beautifully.

Artists like Knight, Zdek Burian, and Rudolph Zallinger created some of the most iconic and detailed dinosaur art of all time.

They filled books and museums with their work, and you can still see many of their murals on display at places like the Field Museum and the Yale Peabody Museum of Natural History.

It's just that, their generation saw dinosaurs as tubby, dimwitted losers in the evolutionary game of life.

By the late 1960s, though, new finds had experts questioning what they thought they knew about dinosaurs.

The key here was the discovery of Deinonychus- the inspiration for Jurassic Park's tenacious "raptors" - by American paleontologist John Ostrom in 1969.

This small carnivore had a stiff, counterbalancing tail, and a wicked, sickle-shaped, "killing claw" on each of its feet.

It was impossible to envision this thing as a sluggish, dumb reptile.

It was nimble and dynamic, even ... one might say...birdlike.

This revelation sparked what came to be known as the Dinosaur Renaissance of the 1970s and 80s.

It opened up old debates and sparked new ones, transforming what we thought dinosaurs were like.

And paleoart went along for the ride!

What paleontologists were doing in labs and museums, illustrators like Greg Paul, Ely Kish, Douglas Henderson, and more were doing with their sketches and paintings.

In the work of these artists, dinosaurs' tails were lifted off the ground, their postures were adjusted, and they were shown running, jumping, clawing, and biting with greater vigor than ever before.

And of course, as with anything that evolves, our image of dinosaurs hasn't stopped changing.

These days, paleontologists are finding more dinosaurs than ever.

In fact, a new species is now being named, on average, every two weeks!

But more importantly, we're learning a lot more about dinosaur biology, like their anatomy and physiology.

In addition to fossil bones, researchers are now studying things like skin impressions, feathers, and other soft tissues -- giving us a fuller picture of not only how these animals looked, but how they moved and what they could, and couldn't, do.

In particular, the discovery of dozens of dinosaurs with feathers and fuzz has totally changed how we see some of our favorites.

And recent paleo-artwork has reflected these changes.

Artists like Julius Csotonyi, Gabriel Ugueto, Nobu Tamura and Emily Willoughby are incorporating the latest insights from the field, and they're also using new technology, like 3D scans, to re-create dinos in more detail than ever.

Where paleoartists of old worked with paint and lithographs, many modern artists have gone digital, rendering new visions of prehistoric life as soon as they're announced.

What really sets these modern paleoartists apart is how they draw on the traditions of previous generations, while also challenging the tropes and ideas that came before.

Paleoart is now in its great Experimental Phase, reflecting what we expect dinosaurs were like, while also speculating about what we don't yet know.

But the lesson here isn't that modern paleoart is right, while earlier editions were wrong.

The art of dinosaurs is always a reflection of the time it's made in.

Just as dinosaurs themselves evolved, so have our thoughts about their lives.

Paleoart is a living document of these alterations.

We've come a long way from the days when we thought the fossils of dinosaurs represented a race of giants, or big lizards, or bulky pseudo-mammals.

And a hundred years from now, natural historians may look back on the illustrations we use today and marvel at just how wrong we were.

Thankfully, the more science reveals to us about the nature of the non-avian dinos, the closer we get to representing the truth in our illustrations.

But as long as dinosaurs remain extinct, there might always be a little part of them that we'll just have to imagine for ourselves.

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