Dinosaurs terrorized Earth’s lesser creatures for nearly 200 million years. But many details of their daily lives are lost to history forever—or at least until a reliable time machine is built.

Don’t let that bum you out, though, because scientists are really good at gleaning loads of information from the most seemingly inconsequential remains. From ulcers to foreplay, these scenes of dinosaurian daily life probably won’t be in the next Jurassic Park.

10 They Suffered From Parasites And Ulcers

Fossilized poo nuggets (aka coprolites) reveal surprisingly valuable information.

The ancient feces show that the ruthless reptiles suffered the same affliction as your cat: parasites. Fecal remains from a fossilized Iguanodon graveyard in Belgium were loaded with cyst-causing Entamoeba organisms as well as trematode and nematode worm eggs, parasites that remained mostly unchanged in the intervening 125 million years.^[1]

Not even the tyrant king T. rex was immune from tiny invaders. Researchers have on occasion found holes in Tyrannosaurus jaws, which they attribute to protozoans, little single-celled parasites that cause ulcers and lesions in the mouth and throat.

9 Some Land Dinosaurs Swam After Prey

If the carnivores weren’t terrifying enough, there’s evidence that some of them could even swim after their prey.

One such scene is immortalized on a river bottom in Szechuan Province. It’s left behind by a theropod, a three-toed predator a la T. rex but smaller. It swam for about 15 meters (50 ft), scratching a series of claw marks in pursuit of quarry that jumped into the water.

Each mark shows the impression of three parallel claws. And not in a haphazard cat-in-the-bathtub way, but in a “coordinated, left-right, left-right progression.”^[2]

So not only were theropods assassins on land, but they could traverse water capably as well. It’s possible that swimming was an innate behavior for some dinos, as it is for dogs.

8 Nonflying Birdlike Dinosaurs Ate Flying Birdlike Birds

Researchers found two Sinocalliopteryx so fortuitously preserved that their last meals were still visible.

Sinocalliopteryx was related to Compsognathus, the ankle-biting “Compy” of Jurassic Park and Dino Crisis fame. Only Sinocalliopteryx was larger, up to 2.4 meters (8 ft) long, and covered in a light feathery fuzz. It wasn’t flight-worthy, but it did prey on creatures that were.

In one dinosaur’s stomach, researchers discovered Sinornithosaurus remains from a cat-sized, feathered theropod that could fly short distances. The other Sinocalliopteryx contained two crow-sized primitive flyers called Confuciusornis.^[3]

The avian meals may have been scavenged, but they’re in similar states of digestion. So it’s likelier that Sinocalliopteryx was a skilled killer who terrorized early birds of the Cretaceous about 125 million years ago.

7 Sauropods Had Special Claws For Digging Nests

The lumbering long-necked sauropods had a weird arrangement of claws that were unlike other animals. When their feet were flexed, the claws lined up along the front like scrapers.

Sauropod footprints disprove the better grip hypothesis because the claws weren’t “engaged.” Instead, sauropods might have used their scrapers to excavate trench-like nests in which they safeguarded their eggs.

Sauropods were also potentially good dancers. Researchers analyzed some more footprints in Morocco and recreated the dinosaur tracks. They found that the prints occasionally faced sideways and sometimes almost backward.

Before evolution made them ultra-gigantic, the daintier sauropods could rotate their forefeet for better agility depending on walking speed and center of mass.^[4]

6 Hadrosaurs Communicated Via Built-In Megaphones

Hadrosaurs are the duck-billed dinosaurs, members of the mostly herbivorous, ornithischian (bird-hipped) clade. Nature’s conveyor belt pumped out hadrosaurs in crested and uncrested varieties, with the lambeosaurs sporting crests on their heads.

It wasn’t just for show. The crests’ tube-filled interior acted as a resonating chamber. It amplified hadrosaur vocalizations, which could have coordinated herding efforts, warned off predators, and/or wooed potential lovers.

Some hadrosaurs, like Edmontosaurus regalis of around 73 million years ago, had a jiggly rooster’s comblike thingy on its noggin. Although it didn’t make noise, it probably signaled reproductive health or age or identified different species for mating purposes.^[5]

5 Some Made A Career Out Of Egg Snatching

Oviraptorosaurs (egg thieves) are feathered, beaked, birdlike dinosaurs that include the famous raptors. Most are horrible, but the newest member of the family not so much.

The endearing Gobiraptor minutus prowled Mongolia’s Gobi Desert around 70 million years ago when the landscape was less a desert and more wetland, crisscrossed by rivers and busy with life. Unlike many other theropods, G. minutus secured its niche with a uniquely omnivorous diet.

Its robust beak and strong jaws allowed it to take advantage of all sorts of overlooked food groups. Instead of tearing the flesh from its enemies and friends, it subsisted on small, crunchy dinosaur bar snacks, such as mollusks, seeds, and eggs.^[6]

4 Triceratops Horns Weren’t (Primarily) For Fighting

The Triceratops and its horned ceratopsian kin didn’t earn their menacing horns and fancy frills for protection but for sex appeal.

Researchers argue that the trademark horns and ornate armor serve mainly to differentiate between species and to add sex appeal. They seem like implements of war or thermal regulation but could instead be an evolutionarily efficient way to avoid shacking up with the wrong species.^[7]

Triceratop-esses didn’t waste their time on genetic scrubs. So a set of mighty frills and horns instantly displayed a male’s hereditary health, as tail feathers do for peacocks.

3 Dinosaurs Engaged In Birdlike Foreplay

Not much is known about dinosaur sex, but in at least one way it resembled bird sex. The revelation comes from a bunch of ancient ruts clawed into a hunk of 100-million-year-old limestone.

The “scrape-like dinosaur tracks” are bathtub-deep, more than 1.8 meters (6 ft) across, and curiously end in a claw mark. These 50 or so ruts, which appeared in pairs, confused researchers.

Then they remembered that modern birds leave similar markings as a prelude to mating. To captivate females, males swagger about and scratch the ground to exhibit their nest-building skill. If these ruts are truly the result of “pseudo-nest-building” foreplay, they’re the first evidence of dinosaurian lovemaking habits.^[8]

2 Some Dinosaurs Were Night Owls

Some vertebrates like birds and lizards have a ring of bone around their eyes called the sclerotic ring. Animals that are active during the day have smaller sclerotic rings and smaller pupils that let in less light but allow for greater depth of focus.

In contrast, nocturnal animals feature wide rings and large central apertures relative to eye size. This larger pupil accommodates a higher number of photons for better visibility in low-light conditions.

Based on sclerotic ring remains, the massive, long-necked herbivores were active both day and night, probably foraging during the cooler twilight periods. And raptors (as well as other carnivores) stalked prey by night.

Along with the previously mentioned fact that some dinosaurs could swim, this makes the Mesozoic so much more terrifying.^[9]

1 T. rex Was Surprisingly Stealthy

Despite its size and apparent clunkiness, T. rex may have used ninja-like stealth to ambush foes.

Scientists looked at footprints from a variety of dinosaurs and then plugged the feet into computer simulations. The theropod feet proved to be the strangest. They were elongated and twice as long as they were wide.^[10]

Sounds clumsy, like trying to run in clown shoes. But unlike other feet, they’re the right proportion for “seismic wave camouflage.” This means that the sound of T. rex footsteps wouldn’t have changed with distance, so unassuming prey animals had no idea how close they were to a thrashing. Less ruthless dinosaurs like herbivores lacked this advantage.

+ Young Dinosaurs Lived Unsupervised

The long-necked, trunk-legged sauropods—history’s largest land animals—easily surpassed 30 meters (100 ft) in length.

A juvenile Diplodocus named Andrew reveals how. Young sauropods were more like ancestral species than adults, which had peg-like teeth fixed in broad snouts. The babies had narrow snouts full of spatula-like teeth. Peg teeth and square snouts are great for chewing on soft ferns, but the young spatulate teeth allowed for consumption of rougher foods.

Researchers say that the juveniles may have lived without parental supervision in age-restricted foraging groups, munching away on tough plants that no one else wanted. As a bonus, isolation helped them to avoid getting trampled by the lumbering adults.^[11]

++ Some Dinosaurs Were Adorably Tiny

The name “raptor” inspires dread, but some unique, recently discovered tracks in South Korea reveal an adorable, sparrow-sized raptor that you could hold in the palm of your hand.

The Lilliputian footprints are about 110 million years old and just 1 centimeter (0.4 in) long. Tiny prints like this are rarely found. But here, they’ve been luckily preserved by Cretaceous lake deposits which also safeguarded similarly little tracks left by frogs, birds, and turtles.

These are the smallest dinosaur tracks ever found. They indicate a creature of raptorian persuasion because one claw is lifted, or retracted, while the other two contact the ground. If the newly named Dromaeosauriformipes rarus is indeed a new type of dinosaur and not a chick, it would be the smallest yet.^[12]

Ivan writes about neat things for the Internet. You can contact him at [email protected].

Dinosaurs continue to fascinate us. Every now and then, we discover a fossil that reveals some new facts about their lives—for example, their diets, injuries, or habitats. However, some fossils also reveal evidence of diseases that affected dinosaurs. Yes, these animals had their own illnesses, too, just like every other living creature out there.

The diseases ravaged the dinosaur population and even killed a good number of them. Many of these illnesses are still around today, and some even affect humans, which sort of makes the whole thing more interesting. We also included some early reptiles that lived around the time of the dinosaurs.

10 Dandruff

A 125-million-year-old dinosaur is the oldest creature known to have suffered from dandruff. That dinosaur is the microraptor, a small carnivore that was the size of a modern crow. Scientists have also found evidence of dandruff in two more dinosaurs, the beipiaosaurus and the sinornithosaurus. Both were about two times larger than the microraptor.

The researchers discovered evidence of dandruff by chance while studying how dinosaurs shed their feathers. They found that some parts of the feathers of the fossils contained corneocytes. This was a big deal because corneocytes are also formed when dandruff appears on human skin.

The researchers did not call it dandruff because corneocytes and dandruff were believed to only form on skin and not feathers. The researchers also found that dinosaurs shed their feathers in small bits—just like modern birds—and not in larger pieces as they would have expected for their size.^[1]

9 Cancer

Dinosaurs had their fair share of cancer, too. This was revealed by a study led by Bruce Rothschild of Northeastern Ohio Universities College of Medicine in Rootstown, Ohio. Rothschild and his team made the discovery after scanning 10,000 dinosaur fossils stored in several museums across North America with an X-ray machine.

The researchers found that 29 of the 97 tested hadrosaur bones contained cancerous tumors. To be clear, not all tumors are cancerous. These were considered cancerous because they closely resembled tumors found in human cancer patients.

Researchers do not know why the hadrosaur often ended up with cancer. However, they think it was because of the conifers eaten by these animals. The conifer is a plant with needlelike leaves that is known to contain cancer-causing chemicals.^[2]

8 Malaria

Malaria has been killing living organisms since the time of the dinosaurs. In fact, some researchers like George Poinar Jr., an entomologist (a scientist who studies insects) from Oregon State University, even think it killed dinosaurs.

Interestingly, this version of malaria was transmitted by flying insects that were probably not mosquitoes. Researchers know a now-extinct midge, a small flying insect that lives in riverine areas, did transmit this earlier version of malaria 140 million years ago. However, they also suspect that sand and horseflies also transmitted malaria.

These flying insects would have bitten the dinosaurs, which they probably considered a major source of blood, the way the female Anopheles mosquito considers humans its primary source of blood today. The flies infected the dinosaurs with an extinct version of malaria called Paleohaemoproteus burmacis.

While the malaria definitely made the dinosaurs sick, Poinar does not think it could have made the dinosaurs go extinct.^[3]

7 Cataracts

There is no hardcore evidence that dinosaurs had cataracts. However, the theory was suggested by L.R. Croft in his book, The Last Dinosaurs. In fact, he says the widespread formation of cataracts made dinosaurs go extinct.

Croft claimed that these creatures started suffering from cataracts when excessive heat and dangerous ultraviolet radiation from the Sun caused global warming. The dangerous radiation also caused dinosaurs to develop cataracts, which later led to blindness. So many dinosaurs went blind that they soon went extinct after becoming unable to fend for themselves.

Croft argued that mammals and reptiles did not go extinct because they cleverly avoided the Sun and switched to hunting in the dark. However, the dinosaurs continued roaming during the day.

However, a lot of people do not think that dinosaurs went extinct after developing cataracts. Natural selection would have made the dinosaurs develop some form of protection against the dangerous radiation. Besides, the whole theory seems weird.

But that is what you get when you ask an ophthalmologist like L.R. Croft why dinosaurs went extinct.^[4]

6 Osteoarthritis

Osteoarthritis is the most common type of arthritis that affects humans today. It sets in when the slippery cartilage at the ends of bones wears out, causing the harsh bone joints to come into direct contact with each other. This causes friction between the ends of the bones, which soon wear out. Pain sets in at this point.

Researchers have discovered that the Caudipteryx, a small flying dinosaur that was just as big as the modern peacock, suffered from this condition, too. In fact, the dinosaur, which lived 130 million years ago, is the oldest creature known to have suffered from osteoarthritis.

Researchers made the discovery while studying the ankle bones of several birds and flying dinosaurs held in Chinese museums. They discovered that 3 of the 10 fossils of the Caudipteryx had the condition. However, researchers do not know why the dinosaur was susceptible to the condition. Interestingly, many small modern birds also suffer from osteoarthritis.^[5]

5 Osteomyelitis

In 1997, researchers exhumed the remains of a Lufengosaurus huenei that lived 170–200 million years ago. They observed that the ribs of the dinosaur were somewhat abnormal. Several parts were missing, indicating that it had suffered some injuries before its death. However, the researchers did not really deliberate on the cause of the injuries and just kept it in storage.

Two decades later, researchers restudied the fossil and determined that the rib injuries were caused when the dinosaur was attacked by a larger predator that was trying to eat it. The team could not confirm the identity of the predator. However, it would have been huge considering that the Lufengosaurus huenei was also enormous. It reached 6 meters (20 ft) in length and weighed almost two tons.

The Lufengosaurus huenei got away from the predator but with a terrible rib injury that soon got infected with some deadly bacteria. The bacteria caused pus to form inside the rib bones, resulting in a deadly bone disease called osteomyelitis.

In humans, osteomyelitis is caused by Staphylococcus aureus. However, the researchers did not confirm whether the bacteria also caused the bone disease in dinosaurs. Nevertheless, the disease could have caused severe fever, fatigue, and nausea in the dinosaur, subsequently leading to its death. Some of the bacteria could have escaped into the brain, making the animal’s demise swifter.^[6]

Curiously, the dinosaur could have still had the condition even if it was not bitten. The bacteria could enter its body some other way and travel into its rib bones through its blood.

4 Septic Arthritis

The hadrosaur, a herbivorous duck-billed dinosaur, seemed to be one unfortunate creature that suffered from a myriad of diseases. Besides cancer, it also suffered from septic arthritis, a severe condition that could have caused pain in its joints.

Unlike the osteoarthritis we mentioned earlier, septic arthritis is caused when germs travel through the blood to reach the joints. Septic arthritis can also be directly introduced into the joints during injury. In either case, it causes severe pain in the joints, sometimes immobilizing them.

Researchers discovered evidence of septic arthritis in dinosaurs while analyzing the elbow fossil of a hadrosaur. They found three unusual growths at the joints which were caused by septic arthritis. Scientists could not confirm how the hadrosaur ended up with the disease. However, they believe that it was so painful that the animal had difficulty walking.^[7]

3 Intestinal Worms

Dinosaurs suffered from several parasitic worms, including tapeworms and trematodes. Researchers do not know how long these tapeworms became, but they think they could have reached 30 meters (100 ft), which is actually small when talking about dinosaurs. Tapeworms reach over 24 meters (80 ft) in humans.

It is almost impossible to find evidence of parasitic worms in dinosaur bone and skin fossils because the worms probably died and decayed after the demise of the dinosaur. However, we can determine the kinds of worms that lived in dinosaurs by analyzing the coprolites (poop fossils) of the dinosaurs. Coprolites sometimes contain worm eggs or cyst samples.

This was how researchers George Poinar and Arthur Boucot discovered the first evidence of dinosaur worms in 2006. The poop belonged to an unidentified carnivorous dinosaur that lived somewhere in modern Belgium. The researchers found evidence of trematode and nematode worms along with a protozoa suspected to be Entamoeba.^[8]

2 Tooth Decay

The Labidosaurus hamatus (aka the lipped lizard) is one extinct creature we have probably never heard of. It was a 1-meter-long (3 ft) reptile that lived around the time the dinosaurs roamed the Earth. However, it is popular for other reasons. It is the earliest creature known to have suffered from toothache and decay.

We discovered this a few years ago when Robert Reisz of the University of Toronto Mississauga led a team of researchers to scan the lower jaw of a fossilized Labidosaurus hamatus. They discovered that the creature had suffered from severe tooth decay that caused it to lose a good number of teeth.

Researchers do not know how the jaw got infected even though they think it had to do with the animal’s diet. The Labidosaurus hamatus was an omnivore. However, its main diet consisted of plants. Herbivores and omnivores with a predominantly vegetarian diet often have teeth specialized for chewing.

This was a major disadvantage for the Labidosaurus hamatus. Excessive chewing wore down its enamel, leaving the nerves inside the teeth exposed. The nerves got infected with bacteria, causing the damaged tooth to develop an abscess. This caused a painful toothache and, consequently, tooth decay.^[9]

1 Tuberculosis And Pneumonia

Pneumonia and tuberculosis predate even dinosaurs. The earliest evidence of the lung diseases was found in the Proneusticosasiacus, a marine reptile that lived over 245 million years ago.

Researchers made the discovery after performing an X-ray analysis of a Proneusticosasiacus fossil. They discovered that some of its ribs were abnormal. Injury, cancer, fungi, and scurvy were initially suspected until the team narrowed it down to pneumonia and Pott’s disease, a lethal form of tuberculosis that often affects the bones.

The researchers discovered that the reptile had suffered from the infection for months or even years until it died. However, other scientists say that the fossil really belonged to a Cymatosaurus, a marine reptile that is closely related to the Proneusticosasiacus.^[10]

The Proneusticosasiacus and Cymatosaurus are closely related to another reptile called the nothosaur. This creature lived and bred on land but hunted in water, just like the seals of today. Interestingly, modern seals are the likeliest marine mammals to end up with tuberculosis.

The reign of the dinosaurs on Earth was a lengthy one. For about 165 million years, they dominated every continent, and today they have conquered our imaginations. But they were far from the only animals on Earth. They shared their world with many species just as weird and wonderful as they were, a few you may not be aware of.

And with that, there will be no Archosaurs on this list. The term “Archosaur” refers to the clade in which dinosaurs belong, alongside their modern counterparts, birds and crocodilians. But they used to be even more diverse, including the likes of the flying pterosaurs and some ancient marine reptiles. Everything else is fair game.

It’s hard to say when exactly the first dinosaurs appeared, with estimates ranging from 250 to 235 million years ago. The first true non-avian dinosaurs appeared around 243 million years ago and went extinct 66 million years ago. Any species that could have reasonably existed within this time frame has a chance of being included.

Now, let us take a trip through time to look at some very weird critters!

Related: Top 10 Dinosaur Fossils Frozen In Time

10 The Sort-of Turtle

Sinosaurosphargis yunguiensis lived in what is now southwestern China 243 million years ago. And it looks just like any turtle should, complete with the broadened ribcage. However, unlike many modern turtles, which are protected by very large hardened scales along their back, ancient turtle “shells” often consisted of a multitude of smaller osteoderms—scale-like bony deposits on the skin.

Except Sinosaurosphargis was notably not a turtle. It shared the turtle’s common ancestor, certainly. But it had split off from that lineage millions of years before the first “true” turtles began to appear.

Interestingly, those same bony coverings in this species threw a bit of a wrench into the ideas about turtle shell evolution, as it was something that the actual ancestral turtles notably lacked.^[1]

9 The Not-Quite-First Mammal

Skittering about the arid ground of Late-Triassic France 200 million years ago, the tiny Megazostrodon could be mistaken for a weird rat or shrew. But this little critter holds a lot of significance for many paleontologists.

This little guy is considered a transitional form between the mammal-ish cynodonts and the true mammals, making it one of the most significant discoveries in the study of mammal evolution. Even so, where exactly it fits into the mammalian family tree remains somewhat controversial, as does the debate surrounding when exactly mammals truly became mammals.

Megazostrodon was probably much too busy eating bugs to consider its rather convoluted place in the world, however.^[2]

8 The Tuatara

Okay, okay, I know I’m technically cheating on this one. I’m not actually referring to the modern tuatara—Sphenodon punctatus—but rather the whole Order of Sphenodontia. Because I couldn’t bring myself to choose just one species.

The Sphenodontids were well established by the early Jurassic, just under 200 million years ago, and were once very a very diverse group. They were part of a larger group called the Rhynchocephalians, the sister group to the Squamates (modern lizards and snakes). They were essentially a diverse group of not-quite-lizards, very similar in design but distinct enough to be classed separately.

Unfortunately, though, all the Rhynchocephalians except for just one genus—Sphenodon—ultimately declined and went extinct millions of years ago. Only the tuatara remains, now threatened by human activity.^[3]

7 The Fish Lizard

The ichthyosaurs (literally “fish lizard”) were a very diverse group of marine reptiles that emerged some 250 million years ago.

For the purposes of this list, though, I am including the dolphin-like Stenopterygius, which lived roughly 180 million years ago. The reason for this choice is a particularly well-preserved specimen that shows just how weird these creatures were.

This specimen not only preserved traces of pigment in the skin but also a layer of blubber underneath. While not conclusively warm-blooded, the find is further evidence that these creatures did regulate their own body temperatures to some degree, an important trait for a reptile that regularly dove to the ocean’s depths.

At one point, the ichthyosaurs may have been some of the apex predators of the Mesozoic seas. But, ultimately, they went extinct around 90 million years ago, 25 million years before the non-avian dinosaurs did.^[4]

6 The Beaver-Otter

Castorocauda lutrasimilis is one example of how nature tends to just use the same design motif over and over again. Much of its body was really quite similar to that of the modern beaver, from the flattened, scaly tail to its little webbed feet.

This was no primordial rodent, however. Instead, its narrow skull was fitted with many needle-sharp teeth well-suited for catching fish, not unlike modern otters. Interestingly, the fur of this 164-million-year-old critter is also remarkably similar to that of modern aquatic mammals, replete with guard hairs and a thick undercoat.

Unlike most modern mammals, Castorocauda likely laid eggs, leading some to suggest its lifestyle may have resembled that of the modern platypus.^[5]

5 The Long Lizard

The origin of snakes and the loss of their limbs remains one of the most contentious debates within the paleontological community. So when a fossil of a Brazilian serpentine reptile somehow emerged in Germany under questionable circumstances (considering that it’s been illegal to export fossils from the country since 1942) and was examined, many were understandably ecstatic.

See, most primitive snakes known to science were generally already partially transitioned to limblessness, possessing no more than one set of limbs. This was different. So finally finding a four-limbed snake truly would have been earth-shattering.

But it was not to be. This was Tetrapodophis amplectus, which lived during the Early Cretaceous some 120 million years ago. And it really was just a very long lizard, not a snake at all.

That’s not to say that this critter added nothing to the debate, though. Tetrapodophis was a burrower, and the structure of its tiny limbs has often been compared to those of known primitive snakes. It is now thought that snakes ultimately lost their limbs to become more adept burrowers as this little lizard did.^[6]

4 Ancient Platypus

Yes, they get even weirder.

Modern monotremes descend from a very old lineage, though it’s not very clearly known how old. Estimates for the timing of the split from other modern mammal lineages vary anywhere from the Early Triassic to Jurassic periods. Still, the oldest-known platypus relative, Teinolophos trusleri, can be placed comfortably into the Early Cretaceous about 120 million years ago. After that, many other related species were quick to follow.

Unfortunately, most of these fossils are incomplete. Even so, it has been suggested that the traits that make the modern platypus so dang weird found their start here. Though only one species of platypus remains today, they were once a very diverse group whose reach even extended beyond Australia, as it did with the South American Monotrematum sudamericanum.

Also, one fun fact! Another very strange critter, the echidna, actually split off from a platypus relative anywhere from 20 to 50 million years ago (or even before that).^[7]

3 The Antarctic Sea Dragon

Recently featured in BBC’s Prehistoric Planet, Kaikaifilu hervei was the king of the Late Cretaceous Antarctic seas 66 million years ago.
https://www.sciencedirect.com/science/article/abs/pii/S0195667116303123
Kaikaifilu was a mosasaur, a marine reptile most closely related to modern lizards and snakes. More specifically, Kaikaifilu was a kind of tylosaurine mosasaur, which meant it had a longer, more serpentine body than the comparatively bulky mosasaurine mosasaurs.

Its estimated length was an impressive 33 feet (10 meters) long, the largest from the South Pole, and it was likely the apex predator of the region. Its reign would not last long, however, as the mosasaurs all died out at the end of the Cretaceous.^[8]

2 The “Crazy Beast”

Adalatherium hui certainly had to have made a strong impression on its discoverers to be given its name. And I assure you, it did.

Using the words of lead researcher David Krause: “Knowing what we know about the skeletal anatomy of all living and extinct mammals, it is difficult to imagine that a mammal-like Adalatherium could have evolved; it bends and even breaks a lot of rules.”

This is all to say that this Madagascan critter from 66 million years ago was really, really weird.

For starters, it had more holes in its skull than any other mammal. It had strange teeth unlike those of any other mammal. It had more vertebrae than any contemporary mammal. Also, researchers had one heck of a time trying to figure out how it walked because “the front half… doesn’t match the back half.”

And this seven-pound (3-kilogram) weirdo was probably still a baby!^[9]

1 Primates

Okay, I might be cheating a little again.

Technically, one of the earliest primates (or perhaps one of the earliest direct predecessors), Purgatorius janisae, is known only from fossils dating to just after the Cretaceous extinction event. However, studies have suggested that the genus is likely much older, perhaps dating back to roughly 81 million years ago. So I feel no guilt.

Purgatorius, to put it lightly, looked like someone mixed up a ferret and a squirrel. But it also possessed the flexible ankle and wrist joints that would become a staple in later primates, allowing it to thrive in the treetops and far above most predators.

And things would only get crazier for primates from here.^[10]

Steven Spielberg’s Jurassic Park came out in 1993 and was an immediate success. On its opening weekend in the United States and Canada, it raked in over $47 million, which went a long way to covering its budget of $60 million.

If the scientists who cloned the dinosaurs had had a more limited amount of cash, they might have looked around the modern world to find the dinosaurs’ closest living relatives—birds. And, as a stand-in for the terrifying T. Rex, they could have used one of its nearest kin—the chicken. Granted, the movie might not have had such an impact, but it would have been accurate.

We tend to think dinosaurs went extinct after a catastrophic event 66 million years ago. This is only true of some of them. We can divide dinosaurs into two groups: avian and non-avian. At least some of the avian dinosaurs survived to evolve into birds, and the non-avians disappeared.

Dinosaurs appeared between 243 and 233 million years ago in the Triassic period. They became the lords of the earth, a position they kept for millions of years before an asteroid smashed into the Yucatan peninsula. All the flesh-eating dinosaurs, such as the T. Rex, belonged to a subgroup known as Theropods. Members of this group had hollow bones and three digits on each foot, just like a chicken.

We have a problem with the term “dinosaur” because it covers a broad range of animals. When someone mentions dinosaurs in conversation, we imagine large vicious brutes such as T. Rex or the placid leaf-eating giant Brachiosaurus, but that is not always the case. So let’s explore ten reasons chickens are dinosaurs.

Related: 10 Fascinating Peeks Into The Daily Lives Of Dinosaurs

10 Tyrant Chicken King

Montana is rich in dinosaur fossils, and in 2003, Doctor Jack Horner (the man Doctor Grant was based on in Jurassic Park) found a T. Rex femur bone. A wonderful discovery, but it was too big to fit inside Horner’s helicopter. Taking a practical approach, he broke the femur in half and ferried it to the North Carolina Museum of Natural Sciences.

In North Carolina, the paleontologist, Doctor Mary H. Schweitzer, set to work on the bone. She discovered soft tissue inside. Unfortunately, any DNA had long since degraded, but Doctor Schweitzer could run tests on the proteins in the soft tissue. The analysis showed her that Tyrannosaurus Rex was more closely related to ostriches and chickens than any living reptile.

9 Bones

In our introduction, we said dinosaurs fall into two groups – avian and non-avian. Doctor John M. Rensenberger of the University of Washington and Doctor Mahito Watabe of the Hayashibara Museum of Natural Sciences in Japan did important work that strongly supported this idea.

They looked at the differences in the bone structure of modern mammals and birds. They found that in mammals, including ourselves, the tubes that bring nutrients to bone cells run parallel to each other like train tracks. When they looked at bird bones, they discovered no tube pattern.

Turning their attention to dinosaur fossils, they found two groups. Some dinosaurs—the flesh-eating Theropods—had the same pattern as modern birds like the chicken. Some, the ones that died out, had a pattern like modern mammals.

Fun Fact: The T. Rex had a wishbone, but you would need help in snapping it.

8 Eggs

As far as we know, dinosaurs laid eggs just like modern chickens and other birds. The fossil record is incomplete, but scientists are fairly sure that all dinosaurs laid eggs. As we are using T. Rex as our example of a chicken’s ancestor, we should make it clear that, so far, we haven’t discovered a T. Rex nest. But we have found nests of other Theropods. If T. Rex followed a similar pattern, which is very likely, she probably laid around twenty eggs.

Most of her hatchlings wouldn’t have reached their first birthday, but the ones that did survive would have put on around 1,700 pounds (771 kilograms) a year until they reached full adulthood at 20 years and reached a weight of about 9 tons. A recently hatched T. Rex would have been about the same size as a modern turkey.

7 Feathers

We don’t see flocks of chickens darkening the evening sky as they migrate for the winter. Chickens can fly, of course, but only for short distances and not very high. They prefer not to do it unless they have to.

We tend to link feathers with flight, but the ability to fly isn’t limited to animals with feathers. Feathers help a bird to fly, but this is an adaptation because feathers evolved for different reasons. A feather’s first uses were for insulation, communication (think of a peacock mating display), and acting as a water-repellant.

Many avian dinosaurs had feathers, and it seems many in the non-avian group had them too. The example that everyone uses to show the link between dinosaurs and birds is the Archaeopteryx, a genus of bird-like dinosaurs. This group of creatures lived in the late Jurassic period, about 150 million years ago, and most would have been around the size of a magpie.

A modern chicken would recognize them as fellow birds.

6 Feet

Going back to the movie Jurassic Park, one of the stars of the show was the Velociraptor. At nearly 7 feet (2.1 meters) tall, these were fearsome beasts. In reality, Velociraptors were not nearly so awe-inspiring. In truth, they were much closer in size to a chicken than to an ostrich.

Their similarity to chickens could also be seen if you looked at their feet.

Dinosaurs tended to have three-toed feet that were remarkably similar to modern birds. Analysis of fossil footprints shows that they moved in the same way too. In fact, early finders of dinosaur tracks often assumed that they were looking at bird tracks.

5 Parenting

Most birds take great care of their helpless young. A hen is no exception. She will teach her chicks how to scratch for food and drink, protect them from danger, and keep them warm.

We have fossil evidence suggesting that at least some dinosaurs behaved in the same way. This is perfectly logical, as hatchlings are very vulnerable. Even a baby T. Rex would have needed looking after until it could care for itself; it would need to learn about the world around it and look to its parent for protection.

Some paleontologists have suggested that an adolescent T. Rex probably went through a phase when it hunted differently from full adults. Not yet fully grown, it was probably faster and more agile than mom or dad and so went off hunting different beasts. Teenagers!

Still, like teenagers today, a young T. Rex seems to have moved around with the rest of his family, although we don’t know if he was reluctant to be seen in public with them.

4 Color

Most of us might think that dinosaurs were quite drab—a little like an elephant, perhaps. But feathered dinosaurs could be just as gaudy as modern birds. We know this because fossilized feathers contain melanosomes. Very simply, melanosomes process and store melanin and give an animal its color.

By studying how melanosomes are arranged in different sizes and densities, researchers can accurately recreate what color or combination of colors the dinosaur had.

It’s a pity that we have so few samples to work from, but there are enough to show that a feathered dinosaur could be just as glorious as a Brahma chicken. And for the same reasons—mating displays, communication, and, perhaps, camouflage are all factors for such bold color schemes.

3 Air Sacs

If you’ve ever picked up a chicken, you will have noticed that it is lighter than it should be. This is because birds have air sacs extending from their respiratory system. This system makes breathing more efficient, which is very useful when a bird needs to exert itself and makes their bodies lighter.

But chickens and other birds didn’t evolve this system; they inherited it from dinosaurs. Some dinosaurs were tiny, but others reached truly incredible sizes. The Argentinosaurus, for example, was at least 98 feet (30 meters) long and weighed at least 72 tons.

Some dinosaurs could grow to such incredible sizes due to air sacs making their bodies lighter and more efficient than they would otherwise be.

2 Wings

A chicken’s wings evolved from short forearms that animals used to capture small prey because their ancestors were jumping into the air to grab things above them. Chickens are a good example of an early stage of this process because they often flutter up rather than properly fly.

If you look closely at a chicken wing, you will see that it is simply a collection of fingers fused and folded against the arm bone, just like its dinosaur relative—a Velociraptor.

1 Tooth or Beak?

The expression “rarer than a hen’s teeth” indicates that chickens don’t have teeth. Not only does this save on dental care, but it also makes flying easier—not that chickens have made much of this advantage.

Many of our chicken’s earliest relatives did have teeth, but a beak made things easier. Some Theropod dinosaurs also developed beak-like structures.

An interesting example of this movement from teeth to beaks comes from China. There, a team discovered a dinosaur named Limusaurus that roamed around in the late Jurassic period 160 million years ago. A young Limusaurus had teeth, but as it grew older, it lost them, and its jaw morphed into a beak. This must have been a very strange sight and somewhat painful for the adolescent beast.