A Swift Hunter: Hunting Style and Physical Characteristics

Allosaurus was approximately 12 meters long, and its overall appearance was that of a typical theropod. However, its skull was more slender than other theropods, so it is believed to have been relatively lightweight for its size.
Thanks to its slim build, it was a fast runner, with some theories suggesting it could run at speeds of 30 to over 60 km/h.

There are also theories that it ran at speeds of 30 to over 60 km/h.

Allosaurus was an agile hunter that used this speed to corner its prey.
Its long, sharp teeth were serrated like a saw, making them perfect for tearing through meat.
When it attacked its prey, it is believed to have firmly grabbed it with its three curved, 15-centimeter-long claws on its forelimbs, and then, after biting deeply, it would violently shake its head to tear off the flesh.

Some studies also suggest that Allosaurus may have resorted to cannibalism when prey was scarce.
It is also believed to have lived and hunted in packs, making it a very troublesome opponent for large herbivorous dinosaurs like Stegosaurus.

Unique Skeleton and Physical Abilities

The skull of Allosaurus was long and slender, and it could open its mouth wide.
Computer analysis has revealed that there were holes on the side of its skull that made the bone lighter and helped to distribute force.
It is also believed that these holes may have housed air sacs, similar to those in birds.

The relatives of Allosaurus had a pair of raised bony ridges on their upper jaw, which helped to strengthen the skull.
Above its eyes, it had short, triangular horns that are said to have served no particular purpose and were likely a form of decoration.

It had short, triangular horns above its eyes.

It stood on two long, powerful hind limbs, and it supported its massive body by distributing its weight across four toes (three pointing forward and one pointing backward) on each foot.

It stood on two long, powerful hind limbs, supporting its massive body.

A Hero Born from the Bone Wars

The first Allosaurus fossil was discovered in the 1800s.
This era was a fierce competition in paleontology known as the “Bone Wars,” during which countless dinosaurs were discovered.
However, while many dinosaur finds from this period were fragmentary, Allosaurus is known for having had most of its body excavated.

In Utah, over 40 Allosaurus fossils were found together, suggesting that they had been lured by herbivorous dinosaurs trapped in the mud, only to get stuck themselves.

The Allosaurus specimen “AMNH 5753” became famous for a reconstruction depicting it feasting on an Apatosaurus.
After that, many fossils of various parts and age groups were discovered. One specimen excavated in 1991, known as “Big Al,” was an Allosaurus with an astonishing preservation rate of over 95% of its skeleton still intact.

Even though it was discovered in the early days of paleontology, the abundance of well-preserved specimens meant that Allosaurus quickly became a benchmark for studying subsequent carnivorous dinosaurs.
Even Tyrannosaurus‘s skull was initially reconstructed using an Allosaurus model in its early days.

Impenetrable Defense and the Ultimate Weapon

The greatest strength of Ankylosaurus was its thorough defense.
Its back was covered in a hard, bony shield (osteoderms), like a suit of armor, from which countless horns protruded.
The bones of its skull were also thick, and it even had bony armor over its eyelids, leaving almost no weak points.
This impenetrable defense was like an “unassailable moving fortress.”

An unassailable moving fortress

It is believed that even a large carnivorous dinosaur like Tyrannosaurus would have hesitated to attack a fully grown Ankylosaurus.

Furthermore, at the end of its tail, Ankylosaurus had a giant mass of bone, a hammer known as a “tail club.”
The bones in the latter half of the tail were fused together, forming a stiff handle for swinging the hammer.
This allowed it to swing the club from side to side at a powerful speed, using the flexible muscles at the base of its tail.

It could swing the hammer from side to side at a powerful speed

According to a 2009 study, a single blow from this hammer could generate a force of up to 364 to 718 MPa (megapascals), which was powerful enough to shatter the leg bones of a Tyrannosaurus.
The height of the tail was right at a Tyrannosaurus‘s knee, so a direct hit could inflict serious damage.
Ankylosaurus compensated for its weakness of being a slow walker with this hard armor and powerful weapon, allowing it to thrive for millions of years.

A Mysterious Full Body and a Unique Diet

Despite being so famous, no complete skeleton of Ankylosaurus has ever been discovered, making it a dinosaur shrouded in mystery.
Our knowledge of its appearance is a reconstruction based on fragmentary fossils like skulls and armor, as well as research data from its close relative Euoplocephalus, for which a more complete fossil record exists.

Ankylosaurus was a herbivore with a beak-like snout.
Its teeth were small and weak, so it could not chew hard plants. It appears to have eaten plants, such as ferns, by plucking them with its wide beak and swallowing them almost whole.
According to a 2017 study, it is estimated to have needed about 60 kg of ferns per day.

It is estimated to have needed about 60kg of ferns per day

The Secret of Its Surprising Skull and a History of Success

A CT scan of an Ankylosaurus skull revealed a complex interior of its nasal passages.
The air passage deep inside its nose was divided into eight small chambers, leading to the interesting theory that it functioned as an “air conditioner” to warm and humidify inhaled air, or as a “resonating chamber” to produce loud calls.

Ankylosaurus is one of the most famous dinosaurs of the late Cretaceous period, but one reason a complete skeleton has not been found in over a century is the theory that its population was originally very small.
If this theory is correct, it means that they lived with a limited population even in their heyday.
As evidence, no Ankylosaurus fossils have been excavated from the very end of the Cretaceous period, leading some to believe that it was one of the few dinosaur species that “did not witness the moment of mass extinction.”

Colossal Body and Unique Physical Structure

Among the many sauropods, Apatosaurus was characterized by its sturdy body and neck.
It was approximately 26 meters long and is said to have weighed between 24 and 32 tons, making its size overwhelming.
It is believed to have been heavier than Diplodocus, another member of the Diplodocidae family.

Its long neck, which reached a length of 6 meters, is presumed to have been held up by strong ligaments.

It held up its 6-meter-long neck with strong ligaments.

Another unique feature of Apatosaurus was that its forelimbs were longer than its hind limbs.

It was once believed that such a heavy body would have been crushed under its own weight on land, and a theory that it lived in water was widely accepted until the 1960s.
However, subsequent research has completely disproven this aquatic theory.

The Birth and Disappearance of “Brontosaurus”

Around 1877, when Apatosaurus was discovered, a fierce competition known as the “Bone Wars” was unfolding in the United States.
During this time, a scientist mistakenly identified an Apatosaurus skeleton as a new species and named it “Brontosaurus” or “thunder lizard.”
Brontosaurus went on to gain more popularity and fame than the original Apatosaurus and was featured in many encyclopedias and media for a long time.

However, a later review concluded that Brontosaurus was the same species as Apatosaurus.
Because the name Apatosaurus was registered first, it was given priority, leading to the conclusion that “Brontosaurus did not exist.”

Astonishing Growth Rate and Little-Known Ecology

Apatosaurus’s greatest weapon for protecting itself from predators was its massive size.
In particular, it had large claws on the thumb of its forelimbs and on three toes of its hind limbs, which were highly effective weapons against predators.

Its growth rate was astonishing, and it may have reached adulthood in just about 13 years.
During its juvenile stage, it is theorized to have gained as much as 15 kg per day, which suggests that plants—its food source—were incredibly abundant at the time.

Apatosaurus had pencil-shaped teeth at the front of its square-shaped mouth, but these were not useful for chewing.
It used its teeth like a rake to strip leaves from plants and then swallowed them whole.

It used its teeth like a rake to strip leaves from plants and swallowed them whole.

Also, because an Apatosaurus skull was not found for many years, a relatively similar skull from Camarasaurus was used for its reconstruction.
However, when a complete fossil was discovered in the 1990s, it was found to have had a slender, streamlined face.

New Research and an Unfortunate Dinosaur

Having its skull misrepresented for many years and being called by the incorrect name “Brontosaurus” for so long, Apatosaurus might have suffered an unfortunate fate.
However, in 2015, a new study was published suggesting that “Apatosaurus and Brontosaurus are very likely different species,” leading to an interesting movement to “revive” Brontosaurus.

Apatosaurus’s very sturdy and large skeleton serves as a valuable clue that conveys its impressive presence to the modern world.

Scant Fossils and “Savage” Tooth Characteristics

Currently, the only specimen known as Atrociraptor is the holotype, “RTMP 95.166.1.”
This consists only of the tips of the upper and lower jaws, and a complete skeleton has not been found.
Therefore, its detailed appearance and ecology remain shrouded in many mysteries.

Meat-Tearing Serrations

Based on information from the limited fossil parts, it is known to be similar to its close relative, Saurornitholestes.
However, as a decisive difference, the serrations on Atrociraptor’s teeth were much larger and more developed.

With these saw-like, jagged teeth, it is thought to have been exceptionally skilled at tearing through the flesh of its prey.
This is also tied to the origin of its name, “savage robber.”

Estimated Size and Weight

Although a full skeleton has not been discovered, according to estimates by Gregory S. Paul in 2010, it is speculated to have been a predator with a small but robust build, measuring about 2 meters in length and weighing approximately 15 kilograms.

Taxonomic Changes: Relationship with Velociraptor

When first described, this species was placed in the “Velociraptorinae” subfamily, which includes the famous Velociraptor.

However, subsequent research led to a revision of its classification, and a 2009 phylogenetic analysis resulted in it being placed in the “Saurornitholestinae” subfamily.
This result was also supported by a 2020 phylogenetic analysis, and it is currently considered to be a species closely related to Saurornitholestes.

Era and Environment: Did It Meet Tyrannosaurus?

Its fossils were discovered in the Horseshoe Canyon Formation in Canada.
In terms of geological time, it was a dinosaur that lived during the “Maastrichtian” age, which falls at the very end of the Mesozoic era.

Relationships with Rivals and Formidable Foes

When speaking of the Late Cretaceous, Tyrannosaurus is famous, but Atrociraptor thrived in an era slightly before Tyrannosaurus.
Therefore, it seems they never actually crossed paths with one another.

Among the contemporary carnivorous dinosaurs that lived in the same era as Atrociraptor were species like Albertosaurus, an ancestor of Tyrannosaurus, and it is believed that they engaged in a struggle for survival within the same environment.

The Pioneer of Piscivorous Dinosaurs and the Mystery of Its Diet

The greatest mystery of Baryonyx was its unique diet.
Its mouth was long and slender, like a crocodile’s, and it had a total of 96 cone-shaped teeth in its upper and lower jaws.

It had a total of 96 cone-shaped teeth in its upper and lower jaws.

Because its teeth lacked the serrations used by other carnivorous dinosaurs to tear meat, it was initially believed to have been incapable of attacking and taking down large animals.

However, the discovery of a half-digested fish fossil in its stomach drew attention to Baryonyx as a very rare dinosaur that primarily ate fish.
Like its relative, Spinosaurus, it is believed to have caught and eaten fish in a similar way to modern bears.

On the other hand, the discovery of an undigested Iguanodon bone in its digestive tract revealed that it was not exclusively piscivorous and also ate the meat of land-dwelling herbivorous dinosaurs.
It would have used the sharp claws on its forelimbs to attack other dinosaurs when it had the chance.

Hunting Style and Physical Characteristics

The neck and jaw of Baryonyx were long and slender, very similar to a crocodile’s.
It likely used its long, low-resistance snout to quickly snap at its prey.
This crocodile-like snout and tooth shape were a crucial clue for identifying its relatives, such as Spinosaurus and Suchomimus. Even today, the existence of Baryonyx is indispensable for research on these dinosaurs.

Baryonyx’s forelimbs were large for a theropod, and it appears to have had great arm strength.
Its large, curved thumb claw is believed to have been used to hook fish or to slash the bellies of prey.

A fossil of a Baryonyx claw

An Unexplained Full Picture and Future Outlook

The Baryonyx fossil was discovered in 1983 by amateur fossil collector William Walker.
Only one specimen has been found, but it is well-preserved, with about 70% of the bones identified.
However, a complete skeleton has not yet been assembled, and its full appearance remains a mystery.

In recent years, new research on its relatives has sent shockwaves through the scientific community. There may come a day when new information about Baryonyx is revealed that we do not yet know.

Size and Characteristics of Brachiosaurus: The Unconventional Physique of the “Arm Lizard”

Brachiosaurus was a super-massive sauropodomorph (herbivorous dinosaur) that lived primarily in North America during the Late Jurassic period.

An Exceptional Style with Long Forelimbs

While typical sauropodomorphs (like Diplodocus) had long hind limbs and a horizontal back, Brachiosaurus was the exact opposite.
Its forelimbs (humeri) connected to the shoulders were developed to be extremely long and thick, while its hind limbs were only about half that size.
It is such an exceptional case among sauropodomorphs that the discoverer initially mistook the forelimb bones for the hind limb bones.
Because of this, its backline sloped backward from the shoulders to the hips like a slide.

Its backline sloped backward from the shoulders to the hips like a slide

Differences from “Giraffatitan”

After the first fossils were discovered by Elmer Riggs in Colorado, USA, in 1900, similar giant fossils were also found in Tanzania, Africa.
Although considered the same species for many years, the African specimens are now distinguished as a separate genus, “Giraffatitan.”
The image of Brachiosaurus that we are so familiar with often heavily reflects the appearance of this Giraffatitan.

The Truth Behind Its Biggest Mystery, the “Neck”: Was Raising It Vertically Impossible?

In encyclopedias and movies, the image of it stretching its neck high vertically like a giraffe to eat tree leaves has been popular.
If raised to the maximum, it would reach a height of 16 meters (about the 5th floor of a building).
However, recent research flatly denies this iconic image.

Reason 1: The Fear of Fainting from Dizziness

Sending blood against gravity to a brain over 10 meters high would require a powerful heart and incredibly high blood pressure.
It is pointed out that if it suddenly raised its neck from a low position, blood would not reach the brain, highly likely causing severe lightheadedness and causing it to faint and collapse.

Reason 2: Skeletal Limits and the “Suspension Bridge” Theory

CT scan investigations revealed that the inside of the neck bones (cervical vertebrae) were sparse cavities, with the thinnest parts being less than the thickness of a postcard.
It would be impossible to attach massive muscles to support the neck vertically.
Currently, the leading idea is the “suspension bridge theory,” where the hind limbs and pelvis act as main towers, suspending everything from the neck to the tail with strong ligaments.

The “suspension bridge theory” suspending from neck to tail with strong ligaments

The “Horizontal Posture Theory” Derived from 3D Simulations

In 2005, a 3D analysis by Michael Parrish and others revealed that the range of motion for moving the neck up and down was at most about 20 degrees from the horizontal.
On the other hand, because the side-to-side range of motion was wide, the current mainstream view is the “horizontal posture theory,” which suggests they ate by sweeping across a wide range of plants while keeping their massive bodies still and their necks at an angle close to parallel to the ground.
Furthermore, the action of “standing up on only its hind legs,” as depicted in the movie “Jurassic Park,” was physically impossible because its hind legs were too short.

Why Did They Evolve Such Long Necks?

If it wasn’t for eating leaves from tall trees, why did they make their necks extremely long, even bearing disadvantages like the risk of fainting and restricted movement?

The hint lies in the fossils of their young (juveniles).
A child’s neck was not as long as an adult’s.
Features that develop significantly as an animal reaches adulthood are biologically considered to be “sexual appeal (display) for reproduction.”
In other words, a prominent theory is that they evolved their necks as a sign of strength and maturity, prioritizing the reproductive advantage of “the longer the neck, the more attractive to the opposite sex” over practical life benefits.

The Phantom Aquatic Lifestyle Theory and the Life of a Giant Glutton

Complete Refutation of the Aquatic Lifestyle Theory

It was once thought that “to alleviate their heavy body weight with buoyancy, they lived in the water of swamps and lakes, exposing only the nostrils on the top of their heads.”
However, it has been discovered that if their massive bodies submerged in water, water pressure would crush their lungs, making breathing impossible. Furthermore, it was found that their nostrils were located at the front (snout) rather than on top of the head. Today, it is confirmed that they lived entirely on land.

A Diet of Eating for 20 Hours a Day

Brachiosaurus was a purely herbivorous dinosaur.
In a very small skull—only about 50 cm relative to its body—grew teeth shaped like pencils or spatulas.

How They Ate

Without chewing, they used their thick mouths to bite off conifers and ferns, swallowing them whole in large quantities.

Digestion

They swallowed “gastroliths” (stomach stones) to help grind up the food and aid digestion.

Eating Time

To obtain energy from low-nutrition plants, they spent about 20 hours a day eating.

It is thought that they had an extremely high energy efficiency due to a mechanism called “gigantothermy,” where their massive bodies experienced little temperature fluctuation (or they were warm-blooded animals with a high metabolic rate).

Moving in Large Herds and Defense

Based on dense clusters of fossilized footprints, it is believed they possessed the sociality to travel in large herds of hundreds.

Brachiosaurus moving in a herd

They maintained a rational cycle of migrating to areas abundant in food.
Also, when predators like Allosaurus appeared, it seems they used their massive bodies as shields and swung their long tails like whips as weapons.

The Jurassic Giant Holding Evolutionary Mysteries

Although fossils of Brachiosaurus are rarely found outside Late Jurassic strata, their lineage was passed down for a long time, as related species have been confirmed even in the Early Cretaceous.
The debates surrounding their unique proportions with long forelimbs and the angle of their necks continue to fascinate many people today.
With new discoveries in the future, the image of this great “arm lizard” will surely be updated into something even more astonishing.

The Origin of “Meat-Eating Bull” and the Mystery of Its Horns

The scientific name Carnotaurus means “meat-eating bull” in Latin.
As the name suggests, their most distinctive feature is their head.
With a face reminiscent of a bulldog—tall vertically and compressed horizontally—it possessed two thick horns protruding sideways above its eyes.
Its appearance is truly that of a “bull in the shape of a lizard.”

It had two thick horns protruding sideways above its eyes.

It is extremely rare for carnivorous dinosaurs to have such horns, and their purpose has long been a mystery.
Since they lacked the strength to be used as weapons, the prevailing theory today is that they functioned as “intra-specific display.”
It is believed that the size of the horns was used as an appeal point to attract females or to intimidate rival males.

The “Ultimate Tiny Arms”: More Vestigial Than Tyrannosaurus

Essential to discussing Carnotaurus are its extremely vestigial forelimbs.
While Tyrannosaurus is famous for its small arms, Carnotaurus takes this to the extreme, with arms measuring only about 50 cm long.

Its forelimbs were only about 50 cm long.

The elbow and wrist joints were fused, making it look at first glance as if the hand grew directly from the upper arm.

However, they were not simply degenerate.
While many advanced theropods reduced their digit count, Carnotaurus retained a primitive “four fingers.”
Even more surprisingly, despite the arms being minuscule, the shoulder girdle was well-developed, revealing that the range of motion in the shoulder was remarkably wide.
The purpose of these bizarre forelimbs remains even more shrouded in mystery than the horns.

The Fastest Giant Hunter on Land? Astonishing Physical Abilities and the “Caudofemoralis”

Contrary to its strange appearance, recent research has revealed that Carnotaurus was likely a hunter possessing terrifying physical capabilities.

According to a 2011 study, Carnotaurus is considered one of the “fastest dinosaurs,” boasting top-class speed among all large theropods.
The basis for this is the size of the “caudofemoralis,” a muscle extending from the tail to the thigh.
Research suggests that the caudofemoralis of Carnotaurus was among the largest of any animal on Earth.

Its caudofemoralis muscle was among the largest of any animal on Earth.

It is believed that this robust muscle generated explosive propulsion, allowing for tremendous charging power like a bull.
However, in exchange for this massive muscle, the tail had low flexibility, and it is presumed that it could not turn very tightly.
It may have specialized in a style of closing the distance instantly with overwhelming straight-line speed to deliver a powerful strike.

It boasted top-class speed among large theropods.

Proof of “Scales” in the Age of Feathers

In recent years, the theory that “carnivorous dinosaurs had feathers” has become common, but regarding Carnotaurus, it is asserted that it “almost certainly did not have feathers.”

This is due to the exceptionally good condition in which the Carnotaurus fossil was discovered.
Fossils discovered in Patagonia in 1985 preserved clear impressions (traces) of “scaly skin.”
This confirmed that Carnotaurus had reptile-like scale-covered skin, making it an extremely important resource in the study of the Abelisauridae family.

One of the Largest Species of Abelisauridae

Carnotaurus is estimated to have been approximately 7.5 to 9 meters long and weighed 1.35 to 2.1 tons.
It was once considered the largest among abelisaurids, but in recent years, a species called Pycnonemosaurus has emerged as a rival.
Regardless, Carnotaurus undoubtedly possessed a massive body representing this group.

Thanks to the well-preserved complete skeleton and even skin traces, Carnotaurus is particularly well-studied among the Abelisauridae.
Its unique appearance and abilities tell the story of how diverse dinosaur evolution was, exceeding our imagination.

Discovery and the “Missing Link” Debate

The Compsognathus fossil was discovered in 1859 in the Solnhofen limestone quarry in Bavaria, Germany.
This geological formation is world-renowned for its exceptionally well-preserved fossils, and the Compsognathus skeleton was found in a near-complete state.

A Fateful Encounter with Archaeopteryx

The impact of Compsognathus’s discovery on the paleontological community was not just due to its small size.
From the same rock layer and at roughly the same time, the fossil of “Archaeopteryx” was discovered.

Archaeopteryx

Archaeopteryx caused a sensation as the “missing link” between reptiles and birds, as it possessed dinosaur-like sharp teeth and claws, yet also had feathers unique to birds.

The discovery of these two fossils led scientists like Thomas Huxley to realize the striking skeletal similarities between Compsognathus and Archaeopteryx.
This fact strongly supported the hypothesis that “birds evolved from dinosaurs,” and for many years, Compsognathus was thought to be the dinosaur most closely related to the ancestors of birds.

A Chicken-Sized, Agile Hunter

Compsognathus was one of the smallest dinosaurs of the Jurassic period.

Astonishing Smallness and Speed

Its maximum length was only about 1 to 1.4 meters, and it weighed only 2 to 3 kg (about the same as a one-year-old child).
Its head was smaller than a human palm, about 10 cm, and more than half of its body length was taken up by a long, whip-like tail.

More than half of its body length was taken up by a long, whip-like tail.

However, its small body was a highly sophisticated weapon for hunting.
There is no doubt that it was an extremely agile dinosaur, with a slender, delicate build and developed hind limbs.
A 2007 study estimated its running speed could have reached 64 km/h (though dinosaur running speeds are still debated).

Its running speed is estimated to have potentially reached 64 km/h.

The long tail, which made up a significant portion of its body length, functioned as a balancer when running at high speeds.

“Delicate Jaw” and Small Teeth

The name “delicate jaw” is derived from its long, lightweight skull.
Its mouth was lined with numerous small, sharp teeth, which were suitable for holding prey, but they were not robust enough to tear flesh or crush bone like larger theropods.

Its teeth were small and suited for holding prey.

The Mystery of the Fingers

The fossil hand discovered had only two fingers, which was initially thought to be their characteristic trait.
However, later research indicated that a third finger was likely present but was either lost during the fossilization process or had become very small and vestigial.
Although the forelimbs were short, they were solidly built and had large claws, believed to be used for powerfully grasping prey.

It had large claws on its forelimbs.

Diet as Told by Fossils: Swallowing Lizards Whole

With its small body, it was, of course, unable to hunt large herbivorous dinosaurs.
Compsognathus is believed to have primarily fed on insects and lizards smaller than itself.

The Last Meal Preserved in the Stomach

This fact is supported by the exceptionally well-preserved fossil.
The German specimen discovered in 1859 was found to have the complete skeleton of a lizard (later named Bavarichthys) preserved in its stomach area, believed to be its last meal.
This is definitive proof that they actively hunted agile small animals.

The Feather Mystery: Why Have No Traces Been Found?

Because Compsognathus lived in the same time and region as Archaeopteryx, and many of its close relatives have been found with feathers, it is strongly suggested that Compsognathus was also covered in feathers.

However, despite the Solnhofen limestone being an excellent environment capable of preserving even the traces of feathers, no clear feather impressions have been found on Compsognathus fossils.

Evidence for the Feather Theory

The fossil of Sinosauropteryx (a close relative of Compsognathus) found in China had clear traces of feathers.
Because of this, many researchers believe Compsognathus must have had feathers too.

Counterargument (The Scale Theory)

On the other hand, since no feather traces have been found, the theory that it was covered in scales, like a modern lizard, is also considered plausible.

This “feather mystery” is one of the biggest controversies surrounding Compsognathus, and further research is awaited.

Evolutionary Classification and the Surprising Link to Tyrannosaurus

Compsognathus is classified as a member of the Coelurosauria group.
This group flourished alongside dinosaurs like Allosaurus in the Jurassic, and eventually evolved into Deinonychus, Velociraptor, and even the Tyrannosauridae lineage.

Although initially thought to be a direct ancestor of birds, current research places it within the Tetanurae group (which includes many carnivorous dinosaurs) and not directly related to birds.
Furthermore, a paper published in 2023 proposed that Compsognathus belongs to the Tyrannosauroidea superfamily. This raises the possibility that this chicken-sized, agile hunter was a distant relative of the strongest dinosaur of a later age, Tyrannosaurus.

Compsognathus is an extremely important dinosaur, holding a major key to the mystery of dinosaur evolution within its small body.

The Surprising Ecology, Different from the Movies

In the movie Jurassic Park, Dilophosaurus was portrayed as a venom-spitting dinosaur, but no evidence of this has ever been found.

Dilophosaurus was about 5 to 7 meters long and slightly taller than a human, which made it one of the largest carnivorous dinosaurs of the Early Jurassic period.
Despite its slender build, it was a typical theropod, with a mouth full of sharp, thin teeth and sharp claws on its forelimbs.
Its teeth were well-suited for slicing soft meat, and it has been suggested that it may have been a scavenger.
Furthermore, because its upper jaw curved like a hook, it is also believed to have played a role in holding open space when it put its head into an animal’s carcass to eat its internal organs.

The Mysterious Role of the Crests

The two crests that are the trademark of Dilophosaurus were made of bone but were as thin as paper and very fragile, making them unsuitable as weapons.

There are various theories about their role, but the most plausible ones suggest they were used for display among their own kind or as a marker to distinguish them from other species.
It is also known that they had air sacs, so it is possible that they inflated them to intimidate enemies or send signals to other Dilophosaurus.
They may have also served as a “visor” to protect their eyes from strong sunlight.

The Mysterious Role of the Crests

Vast Habitat and Clues to Evolution

The first Dilophosaurus fossil was discovered in Arizona, USA, but a very similar fossil was later found in China.
While the Chinese fossil has now been classified as a separate genus called Sinosaurus, this fact suggests that Dilophosaurus lived in a wide range of areas during a time when the supercontinent Pangea had not yet fully split.

Footprint fossils have also been found in places like Italy, which further suggests that they had a wide habitat around the world.

Discovery by the “Mother of Paleontology”

Dimorphodon first appeared in human history about 200 years ago, in 1828.
Its fossil was unearthed by Mary Anning, a renowned British fossil collector often called the “Mother of Paleontology.”

Because the fossil she discovered was missing its head, it was initially identified as a species of the famous Pterodactylus.
However, when a fossil of its distinctive skull was later excavated, it became clear that this was an entirely new species.

This pterosaur was formally described in 1859 by Richard Owen, the prominent British paleontologist who also coined the word “dinosaur.” He gave it the scientific name “Dimorphodon.”

“Two-Form Teeth” and a Giant Head That Defy Pterosaur Images

Dimorphodon’s most defining characteristic, from which its name is derived, is found inside its mouth.

Two Forms of Teeth

Unlike the “bird-like beak” image many people have of pterosaurs, Dimorphodon’s jaws were lined with many teeth.
Furthermore, these teeth were clearly divided into two distinct shapes: long, sharp teeth at the front of the jaw, and short, small teeth at the back.

Giant Head

Dimorphodon had a particularly large head for a pterosaur, with a short neck.
Its appearance is sometimes described as a “raptor with wings,” giving it a strange, lizard-like impression.

It Has Been Described as a ‘Raptor with Wings.’

However, despite its sturdy appearance, this large skull had a lightweight structure.

The Debate Over Flight and Walking

Dimorphodon was about the size of a seagull, with a maximum wingspan of 1.4m and a body length of only about 1m.
However, due to the imbalance of its oversized head, its flight and walking abilities are the subject of much debate.

Flight Capability

Because its head was large and its wings were disproportionately small, it is believed not to have been a particularly strong flier.
It couldn’t fly by constantly flapping its wings like a bird; rather, while self-powered flight was possible, it is thought to have relied primarily on gliding and descending.

It Is Believed to Have Relied Primarily on Gliding and Descending.

Locomotion

Its body structure suggests that walking on land would have been quite difficult, leading to the assumption that its habitat was the coastline.
Its long tail, which was used for steering during flight, would not have been useful for walking. It is thought that it spent most of its time on land clinging to trees or cliffs.
On the other hand, some theories suggest that its long hind limbs and the claws on its first to fourth toes may have enabled it to walk bipedally.

There Is Also a Theory That It Was Capable of Bipedal Locomotion.

The Diet Debate: Fish-Eater or Land Hunter?

It is certain that Dimorphodon was a carnivore, but what it used its “two-form teeth” for has long been a topic of discussion.

Traditional Theory (Piscivore)

Because closely related species ate fish, the traditional theory held that Dimorphodon lived on the coast and caught fish from the air.

Recent Prevailing Theory (Terrestrial Predator)

However, recent analyses of its jaw shape, poor flight capability, and dental structure strongly suggest that it hunted insects and small terrestrial vertebrates, rather than fish.

If this theory is correct, Dimorphodon may have reigned over the ecosystem of Early Jurassic England as a unique “little hunter” that glided through the air and sometimes moved bipedally on the ground to hunt small animals.