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.

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.

Astonishing Speed and Anatomy

Among ornithomimosaurs, Gallimimus is a large species, second only to Deinocheirus. It measured 4 to 6 meters (13.1 to 19.7 feet) in length, and when standing, its head reached over 2 meters (6.6 feet) high.
While its body size was more than double that of an ostrich, its skeletal structure was lightweight, giving it an estimated weight of only about 400 kg (880 lbs).

The Secret of Its Swiftness

True to its agile appearance, Gallimimus was a highly fleet-footed dinosaur.
With a light body and powerfully developed hind limbs, there are various theories about its top speed. It is estimated to have run at speeds of 45 to over 60 km/h (28 to over 37 mph), with some theories even suggesting it reached 110 km/h (68 mph), matching the speed of a cheetah.
This is a speed comparable to a passenger car driving on a standard road.

The secret to this astonishing speed lies in its unique foot structure.

Flexible Feet

Compared to its ancestral species, the three bones making up the instep of its foot were of different thicknesses.
This structure provided flexibility to the foot and served to cushion the impact when running.

Characteristics of Fast Animals

It possessed the anatomical features of fast-running animals, such as the length of its tibia (shinbone) relative to its body proportions.

A Balancer

Its long tail, which made up more than half of its body length, is believed to have served as a balancer while running.

Its long tail is believed to have served as a balancer while running.

Physical Characteristics and Alert Behavior

Gallimimus had a very small head and a long, slender neck and limbs, much like a bird.
However, among ostrich dinosaurs, it is noted for having a relatively long torso and comparatively shorter forelimbs.

Field of Vision

A 1988 study suggested that Gallimimus’s eyeballs did not move much within their sockets.
Like modern herbivores, its laterally positioned eyes provided a wide field of vision, but it was poor at seeing things in three dimensions (binocular vision).
Therefore, it could not survey its surroundings without moving its neck. It may have constantly bobbed and turned its head around to watch out for predators, much like an ostrich or a pigeon.

Intelligence

Fossilized skulls reveal that it had a large brain, leading researchers to believe that Gallimimus was a relatively intelligent dinosaur.

Life in a Herd

Because individuals of various growth stages have been found clustered together, it is highly likely that Gallimimus formed herds composed of members of different ages and lived collectively.
The scene in the movie “Jurassic Park” where a flock of them flees in a panic from a Tyrannosaurus is iconic, but no conclusive evidence has yet been found to prove that they actually ran around in herds all the time.

A Diet Shrouded in Mystery

Although classified as a theropod, Gallimimus was not a ferocious carnivorous hunter.
Its most defining feature was its mouth; its face was shaped like that of a modern duck, and it had absolutely no teeth in its mouth.

Its face was shaped like a duck’s, and it had absolutely no teeth in its mouth.

Because of this, its exact diet has been the subject of long-standing debate.

The Omnivore Theory (Currently Mainstream)

Today, many researchers lean toward the idea that it was “omnivorous”—meaning it was not specialized for one specific food type, but rather ate primarily plants while opportunistically consuming insects and small animals when available.

Beak and Forelimbs

Its mouth was covered by a toothless keratinous beak that was thin and sharp, a shape well-suited for catching insects, other small animals, lizards, and mammals.
It would also have been ideal for pecking open the eggs of other dinosaurs to drink the contents.

The Role of the Arms

Its arms were long, allowing it to easily grab plants growing on the ground, as well as mammals, lizards, and other small prey.
Its fingertips were unusually well-developed, and it is thought to have been dexterous enough to use its hands like hooks to pull tall grasses and branches toward itself to eat.

The Herbivore Theory

The discovery of what appear to be gastroliths (stomach stones) used for grinding plant matter in its stomach region also supports the possibility that it was a herbivore.
Since it lacked teeth, it is believed to have swallowed foods like nuts and seeds whole, digesting them with the help of the gastroliths in its stomach.

The Filter-Feeding Theory

In a 2001 study, it was suggested that its beak was equipped with a comb-like filter (slits)—the first such discovery in a dinosaur.
This led to the “liquid diet theory” gaining major attention, proposing that it filtered aquatic organisms and microbes in lakes and ponds, feeding much like a flamingo.
However, there are counterarguments based on examples like its close relative Struthiomimus, which was much larger than a waterfowl. Critics argue that filtering aquatic cyanobacteria and small animals alone would not have provided sufficient nutritional volume.

The Discovery of Feathers and “Wings”

For a long time, Gallimimus was depicted as being covered in scales, just as it appeared in the movie “Jurassic Park.”
However, recent research has completely transformed that image.

Traces of Feathers

While traces of feathers have not been found directly on Gallimimus fossils, they have been discovered on its very close relative, Ornithomimus.

The Existence of “Wings”

Most surprisingly, it was revealed that adult Ornithomimus possessed “wings” on their forelimbs made of fully developed feathers with central shafts (quills).
These wings were not for flying, but are thought to have been used for courtship displays or for keeping eggs warm.

Based on this discovery, it is now the scientific standard to believe that as Gallimimus grew, its body became covered in feathers like an ostrich, and it developed wings on its forelimbs.

Additionally, two species of Gallimimus have been identified: *Gallimimus bullatus* and *Gallimimus mongoliensis*.

Relationship with Pteranodon and Its Independence: Why Did the Classification Change?

Geosternbergia’s habitat and time period overlapped with that of the famous Pteranodon, and its form was nearly identical, with the exception of its crest.
For this reason, it has a long history of being treated as a synonym of Pteranodon.
In fact, Geosternbergia sternbergi is still well known to the public by its former name, Pteranodon sternbergi.

However, Geosternbergia lived in an earlier time period than Pteranodon, and clear differences in their crest shapes were confirmed.
In recent years, as taxonomic “splitting” progressed based on the idea that too many species were classified under the genus Pteranodon, Geosternbergia was re-evaluated and recognized as an independent genus in 2010.
Since becoming its own genus, its presence in media and other platforms has also expanded.

The Most Prominent Feature: A Crest Like an Eboshi (Japanese Cap)

Geosternbergia’s most prominent feature is its uniquely shaped crest, resembling an eboshi (a tall, traditional Japanese cap), extending from its head.
This bony crest was located on the parietal bone (top of the skull) and extended upward and backward from the head.

The purpose of this crest is thought to have been primarily for display to attract mates, and it likely served as a visual marker for them to identify other species, or to distinguish age and sex within their own species.

Crest Variations: Differences Based on Species and Sex

The size and shape of the crest varied depending on age, sex, and the two known species.

G. sternbergi

The male’s crest was larger and more vertical, especially in older individuals.

G. maysei

The male’s crest was short, rounded, and vertical.

Females

The crests of females in both species were smaller, narrower, and more rounded than those of the males.

Fossils and Size

Geosternbergia was a large pterosaur with a wingspan reaching 3 to 6 meters.
The fossils discovered include an incomplete adult male skull and a nearly complete lower jaw (approximately 1.25m), among others.
Most specimens have been found in a fragmented state, but enough information has been recovered to reconstruct them in detail.

Astonishing Neck Structure

The most prominent feature of Mamenchisaurus is its abnormally long neck.
In some species, the neck accounted for more than half of the total body length, reaching from 12 meters up to a maximum of 16.9 meters.
This incredible length is a characteristic that sets it apart from all other sauropodomorphs.

Its neck is said to have reached a maximum of 16.9m.

19 Cervical Vertebrae (Neck Bones)

This extraordinary length was achieved by its number of neck bones, or cervical vertebrae.
While typical sauropodomorphs have 15 or fewer cervical vertebrae, Mamenchisaurus had an astounding 19.

Lightweight Strength to Support the Neck

Mamenchisaurus had an amazing physical structure to support a neck of this length.

Lightweighting

Each cervical vertebra was hollowed out on both sides, making them extremely light.
This is a feature also seen in theropods and modern birds, and it was an adaptation to prevent the long neck from becoming too heavy and causing a loss of balance.

Ensuring Strength (Suspension Bridge Structure)

Lightweight bones can be a concern for strength, but Mamenchisaurus’s cervical ribs (neck ribs) overlapped and bundled with the preceding and succeeding bones, creating a “suspension bridge” structure that increased its strength.
This allowed it to have a neck that was both light and strong.

The Debate Over the Purpose of Its Long Neck

So, why did Mamenchisaurus evolve such a long neck?
The purpose of this feature is still debated today.

The “Vertical Movement” Theory (Conventional Theory)

It was once believed that it held its long neck high, like a giraffe, to eat conifers and new shoots from tall trees that other dinosaurs could not reach.

It was believed to eat conifers and new shoots from tall trees.

As its skeletal structure seemed to make lateral movement difficult, this theory suggested it primarily moved its head up and down, monopolizing high-elevation food sources.

The “Horizontal Movement” Theory (Recent Theory)

Recent sauropodomorph research has pointed out that lifting the neck high would require an enormous amount of energy and put a massive strain on the heart.
Detailed analysis of the cervical vertebrae structure showed that it was not suited for lifting the neck vertically, and the “vertical movement” theory has now been discredited.

It is now believed that in order to minimize energy loss, it evolved to seek food by moving its neck. It likely stretched its neck out horizontally to efficiently graze on a wide range of plants (ground cover and low shrubs) without having to move its body.

Regardless of which theory is correct, there is no doubt that Mamenchisaurus utilized its unique neck structure to its fullest advantage to survive the harsh competition for survival.

History of Discovery and Research Progress

Mamenchisaurus fossils have only been found in the Sichuan, Gansu, and Xinjiang provinces of China.

First Discovery and Naming

Mamenchisaurus was first discovered in 1952 at a highway construction site in Sichuan Province, China.
The fossils found at this time were fragmentary and in very poor condition.
It was later named Mamenchisaurus constructus in 1954 by the representative Chinese paleontologist Yang Zhongjian.

Research Progress

Later, based on a well-preserved skeleton discovered in 1957, Mamenchisaurus hochuanensis was described in 1972, revealing the extremely long neck of Mamenchisaurus.
In 1996, a nearly complete, articulated skeleton, including a skull, was also discovered.
These specimens have shown that they were a more advanced species that evolved from dinosaurs like Vulcanodon and Shunosaurus.

Size, Classification, and the “Wastebasket Taxon” Mystery

The genus Mamenchisaurus was also an extremely diverse group.

Gigantic Size

The most well-known species, Mamenchisaurus hochuanensis, was 22m long, but Mamenchisaurus sinocanadorum from Xinjiang reached a length of 35m and a weight of 50 tons, making it one of the largest dinosaurs in history.

Unique Asian Evolution

While long thought to be closely related to Diplodocus, research on the skulls of Mamenchisaurus sinocanadorum and Mamenchisaurus youngi has led to the belief that they were a unique lineage of sauropods that evolved in Asia.
Omeisaurus and Chuanjiesaurus are cited as close relatives.

The “Wastebasket Taxon” Problem

For many years, Mamenchisaurus served as a “wastebasket taxon,” where many long-necked sauropods discovered in China’s Jurassic layers were classified.
However, the type specimen that was first named Mamenchisaurus was actually a very fragmentary fossil.

Therefore, it remains uncertain whether the more complete specimens discovered later truly belong to the “same genus” as the original Mamenchisaurus.
Recent research suggests that many of the species previously classified as Mamenchisaurus are actually likely to be separate, independent genera of dinosaurs.
For example, the massive Mamenchisaurus sinocanadorum is now strongly believed to be a separate genus, Xinjiangtitan.
Scientists are currently in the process of sorting out this taxonomic confusion.

Tail Hammer and “Death Pits”

Mamenchisaurus had other surprising features besides its long neck.

Tail Hammer

Amazingly, the tip of the tail of Mamenchisaurus hochuanensis was found to have a small bone club, formed from several fused vertebrae.
This is thought to have evolved independently of the weapons of Ankylosaurus and may have been used for defense, although some theories suggest it was merely a pathology (a result of injury or disease) or a type of sensory organ.

Skin and Footprints

Skin impressions of Mamenchisaurus have also been found, providing important clues about sauropod skin.
Furthermore, giant footprint fossils, believed to be from a Mamenchisaurid, have been discovered in the Junggar Basin in China.
These footprints, left in volcanic ash-laden mud, eventually became “death pits” where other small dinosaurs became trapped.
Fossils of dinosaurs like Guanlong, which were caught in these footprint traps, have been found, offering a glimpse into the ecology of the time.

Mamenchisaurus and Japan

Fossils of Mamenchisaurus hochuanensis have frequently been exhibited in Japan since the 1980s, making it a very well-known dinosaur in the country.
Currently, a reconstructed skeleton of Mamenchisaurus hochuanensis can be seen at the Fukui Prefectural Dinosaur Museum and other locations.

Also, Moshiryu, discovered in Iwate in 1978, was until recently said to be closely related to Mamenchisaurus, but it is now considered a sauropod of indeterminate classification (possibly a titanosauriform).

With its extraordinary neck length and unique evolution, Mamenchisaurus continues to be an extremely important presence in unraveling the mysteries of dinosaur diversity and gigantism.

The Secret and Purpose of Its Sturdy Head

The “thick head” was initially thought to be a weapon for head-butting in fights between males.
However, this theory is now questioned because there is no mechanism to absorb the impact of a head-butt, and no injuries from fighting have been found on the skulls.

The current leading theory suggests that the head was used as a display to establish dominance among its own kind or to attract mates.
However, this doesn’t mean it was completely useless as a weapon.
It is believed to have used its head to ram the legs or neck of a predatory dinosaur like Tyrannosaurus to defend itself.

The area around the top of its head and its nose was covered in bony horns and knobs, giving it a fully armored appearance.

The area around the top of its head and its nose was covered in bony horns and knobs.

Agile Movements and an Unexplained Full Appearance

The long tail of Pachycephalosaurus was reinforced with ossified tendons, allowing it to be held straight out in the air.
It is believed that this tail helped it balance, enabling it to make agile movements while walking on two legs.

It used its tail for balance, which allowed for agile bipedal movements.

However, a complete skeleton of Pachycephalosaurus has not yet been discovered, so its current appearance is a reconstruction based on data from closely related species where more research has been done.
This means there is still a possibility that a shock-absorbing structure might be found, which would prove that the head-butting dinosaurs from old illustrations were a reality.

The Mysterious Crest: Its Ticket to Stardom

The specific purpose of this unique, 1.8-meter-long crest has been the subject of various theories over the years, and it is still not completely understood.

It had a long crest.

Resonator Theory

The crest was hollow and connected to its nostrils.
When a model was made, it was found that it could produce a very loud sound that could travel for several kilometers, much like a modern elephant.
The pitch of the sound was determined by the length of the crest, suggesting that different species used different pitches to communicate.

If they used sound to communicate, it might have been an effective method for them to “talk” to each other while living in the forest.

Olfactory Amplifier Theory

Another prominent theory is that it was a device that amplified its sense of smell, allowing it to detect scents from a distance.

Display Theory

Since the shape of the crest varied between individuals and genders, it may have been used for mating displays or to establish social hierarchy by showing it off to other members of its species.

A theory once suggested that it was used as a snorkel, but this has since been disproven as there was no opening at the tip of the crest.

Surprisingly Few Fossils and Its Ecology

Parasaurolophus had a large body, with stocky legs and a robust shoulder and hip region, even for a member of the Lambeosaurine family.

It had stocky legs and a robust shoulder and hip region.

Bones extended upward from its spine, giving it a high, arched back.

In contrast to other hadrosaurs like Edmontosaurus and Maiasaura, whose fossils have been found in large numbers, very few Parasaurolophus fossils have been discovered.
This suggests that Parasaurolophus was one of the least numerous dinosaur species and may have lived a solitary life rather than in herds.

Diet and Behavior

Parasaurolophus was capable of walking on two or four legs, but due to its large body, it was not able to move very quickly.

Hadrosaurs had a special dental structure called a “dental battery,” which consisted of many rows of small, packed teeth.
They used their duck-like, broad beak to cut off plants and then used their back teeth to grind them into a pulp for easier digestion.

In recent years, a dinosaur similar to Parasaurolophus was found in China, so it is no longer considered a one-of-a-kind creature.
However, its mysterious crest and enigmatic ecology continue to fascinate many people today.

Giant Wings and an Amazingly Lightweight Skeleton

Pteranodon’s wingspan could reach up to 9 meters, an enormous size unimaginable for present-day flying animals.

Its wingspan Reached a Maximum of 9m.

Despite its colossal size, its body weight is estimated to have been only about 15 to 25 kg, a light weight that was advantageous for flight.

The secret to this incredible weight reduction lay in its skeleton.
Pteranodon’s bones were hollow and extremely thin, and the bones of its torso—the heaviest part of its body—were minimized to the extreme.

It is believed that Pteranodon relied less on muscle power and primarily used a gliding flight style, catching air currents like a glider.
Due to its body structure, it was not suited for swift movements on land.
Therefore, it is thought to have carefully chosen landing spots and launched itself from high points, such as cliffs near the ocean, to glide.

Distinctive Crest and Diet

Pteranodon is characterized by the long, large crest located at the back of its head.

Characterized by the Long, Large Crest at the Back of Its Head.

There are several theories about the role of this crest, and while it is mainly thought to have been used for mating display, the following theories have also been proposed:

Species Identification

A marker for distinguishing members of its own species.

Thermoregulation

An organ for dissipating body heat.

Flight Balance

A structure used to balance the body around the neck as a pivot point, or to detect air currents during flight.

Its beak was long and sharply pointed, but it had no teeth.
It is believed to have primarily subsisted on fish, and its large jaws, similar to a pelican’s beak, suggest it mostly swallowed its prey whole, which would not have hindered its predation.

It Swallowed Its Prey Whole with a Large Beak Like a Pelican’s.

History of Discovery and Habitat

The first Pteranodon fossil was discovered in the 1870s by American paleontologist Othniel Charles Marsh, who excavated numerous wing bones in the Kansas rock layers.
It was initially classified as the toothed Pterodactylus, but the discovery of a toothless skull in 1876 confirmed it as a new genus and it was renamed “Pteranodon.”

It was mainly discovered in North America, but fragments of its fossils have also been found in Japan.
Pteranodon coexisted with its relative Nyctosaurus and the toothed bird Ichthyornis, and is thought to have nested in high places to avoid predators.

The Secret to Its Strength: Its Heavily Armored Body

The secret to Stegosaurus’s strength lies in its heavily armored body.
The four sharp, meter-long spikes on the end of its tail were its weapons for fighting enemies.
In fact, a fossil of an Allosaurus with a wound that appears to have been caused by a spike has been found, confirming that the spikes were indeed used as weapons.

Four sharp spikes on the end of its tail

Additionally, its throat, which at first glance appears defenseless, was covered in over 100 small, pebble-like ossicles, providing a very flexible yet robust armor.
Small bones were also embedded under the skin around its hips, and this heavy armor is believed to have played a crucial role in protecting it from ferocious carnivorous dinosaurs.

The Mysterious Back Plates: A Weapon, or Something Else?

The most distinctive feature of Stegosaurus, its back plates, formed a mysterious shape made of 16 interconnected bony plates.
When fossils were first discovered in the 1870s, the plates were thought to be a defensive weapon that covered its back.
However, this theory was later questioned because the plates were very thin and lacked durability.

A hundred years after the fossil’s discovery, traces of blood vessels were found on the surface of the plates, leading to the theory that they were an organ for thermoregulation, absorbing solar heat and dissipating excess heat.

A theory was proposed that the plates were a thermoregulation organ for absorbing and dissipating solar heat

However, since the number of blood vessels in the plates was limited, their effect was likely minor.
Currently, many paleontologists speculate that the plates had flashy colors and patterns and were used as a display for social signaling or for attracting mates.
That being said, the edges of the plates were as sharp as blades, so their potential use as a weapon cannot be ruled out.
Their function may not have been just one thing.

Small Head and Body Characteristics

Stegosaurus is characterized by its unusually small head relative to its gigantic body.
Studies of its skull have revealed that its brain capacity was only about 28 grams, roughly the size of a walnut.
This makes it one of the smallest-brained dinosaurs ever discovered.

An unusually small head for its huge body

A theory once suggested that it had a “second brain” in its tail, but this has since been disproven.

Its body mass was about 2.5 to 3.5 tons, similar in weight to a modern white rhinoceros.
It had short forelimbs and a distinctive arched posture, with its hips positioned higher than its shoulders.

It lived in an arched posture, with its hips higher than its short forelimbs.

Due to this body structure, it was completely unable to run away from enemies.

A Unique Eating Method

Stegosaurus was a herbivore with a small head, a long snout, and small teeth located only at the back of its mouth.
When eating, it used its sharp beak to pluck low-lying plants from the ground.

It used its beak to pluck plants from the ground.

It would rub its upper and lower teeth together to chew and finely chop the plants.
It is also believed that it had cheek pouches to temporarily hold plucked plants before chewing them.

Summary

Despite the visual impact of its appearance, much about Stegosaurus’s ecology remains a mystery.
However, its heavily armored body is the ultimate proof that it thrived throughout the Late Jurassic period and was widely successful around the world.