Unique Horns and Defense Mechanism

The most distinctive feature of Albertaceratops was the unique arrangement of its horns.
While many other ceratopsians had a large horn on their nose, Albertaceratops had two large horns on its brow and two large horns on the top of its frill.

It had two large horns on its brow and two more on the top of its frill.

These horns are believed to have helped protect it from the biting attacks of Tyrannosaurus.
It may also have swung its head from side to side, using its horns like a pickaxe.

It may have swung its head from side to side, using its horns like a pickaxe.

This unique defense mechanism suggests that Albertaceratops had its own unique survival strategy within its ecosystem.

Confusion Surrounding Its Naming

Before being officially described, Albertaceratops was for a time referred to by the name Medusaceratops.
However, the name Medusaceratops is now used for a different ceratopsian genus.

Thus, based on its unique horn arrangement, it is speculated that Albertaceratops had its own distinct defensive strategy in its ecosystem.
Future discoveries of more fossils are expected to unravel the remaining mysteries of this dinosaur.

Origin of the Name and Basic Data

The scientific name Aquilops is derived from a combination of Latin and Ancient Greek.

Meaning of the Name

Latin for “Eagle” (aquila) + Ancient Greek for “Face” (ops) = “Eagle Face”

Type Species

Aquilops americanus

This specific name was chosen to commemorate the fact that it was the first “very basal neoceratopsian” discovered in the United States.

History from Discovery to Naming: Recognized as a New Species After 17 Years

The first fossil of Aquilops was discovered in 1997.
An expedition supported by National Geographic excavated a single partial skull from the Cloverly Formation (Albian stage) in Carbon County, southern Montana.
The discoverer was paleontologist Scott Madsen.

Was it Mistaken for Another Dinosaur at First?

It was not introduced to the world as “Aquilops” immediately upon discovery.
Initially, while the specimen was undergoing preparation, it was described as a different dinosaur, Zephyrosaurus.
Later, Madsen himself realized it was a new species, but it took a long time for it to be formally recognized.

Finally, in 2014—17 years after its discovery—it was named and described by Andrew Farke and colleagues, etching the name Aquilops into history.

Only 60cm Long! Physical Characteristics of the “Eagle Face”

Aquilops was a very small dinosaur.
According to estimates by paleontologist Mathew Wedel, its dimensions were as follows:

• Total Length: Approx. 60 cm
• Weight: Approx. 1.5 kg
• Skull Length: 84.2 mm (Holotype specimen OMNH 34557)

Unique Features Proposed by the Describers

As its name implies, Aquilops possessed unique facial features.

An Eagle-like Beak

This is the most defining feature of Aquilops.
The bone core of the beak curves downward, and the front possesses an arched keel with a bump.

Distinctive Dentition

The tooth row in the back of the upper jaw, when viewed from the front, is longer than the entire length of the depression seen from the side.

Pointed Antorbital Fenestra

The antorbital fenestra (the opening in front of the eye socket) is twice as long as it is tall, pointing backward and extending beneath the eye socket.

Classification and Evolution: Between Psittacosaurus and Protoceratops

Taxonomically, it is considered to have occupied a position more advanced than the famous ceratopsian Psittacosaurus, but more primitive than Protoceratops.
As a very basal neoceratopsian, it is a crucial piece of the puzzle in understanding the evolutionary process of horned dinosaurs.

Remaining Mysteries: No Frill or Body Found?

Many mysteries still surround the detailed ecology of Aquilops.

Only “Part of the Head” Has Been Found

To date, only a partial skull including the upper and lower jaws has been discovered.
Most of the back of the head and the palate are missing. Not only are the body bones—necessary to know the dinosaur’s full appearance—missing, but even the “frill,” a symbol of ceratopsians, has not been found.

The Specimen Was Likely a “Child”

Furthermore, the discovered holotype specimen itself is likely not a fully mature individual, but a “sub-adult.”
Studies comparing it with related species suggest this specimen was about 60% of the size of an adult.

In other words, the Aquilops we know is still in the growth phase, and no one yet knows what a fully grown adult looked like.

Hopes for Further Discoveries

Due to the extremely low number of specimens—and the fact that only partial sub-adult fossils have been found—the full picture of Aquilops remains unclear.
To understand the true appearance of this mysterious dinosaur with the “Eagle Face,” further fossil discoveries are essential.

“Pointed Lizard”: The Misunderstandings and Truths Hidden in the Name

The scientific name Centrosaurus means “pointed lizard” in Greek.
Looking at their characteristic “large single horn on the nose,” the name seems fitting, but there is actually a somewhat complex story behind it.

Not a Nose Horn, but “Part of the Frill”?

At the time of naming in 1904, the specimen referenced was not the nasal horn but “part of the frill.”
Researchers mistakenly interpreted a hook-like projection on the rear edge of the frill as a “horn on the nose.”
The misunderstanding was later cleared up, but since they actually possessed a magnificent nasal horn, the name and the reality ended up matching perfectly.

Confusion Over the Name

Also, since the name was already used for a type of lizard at the time of naming, an attempt was made to rename it “Eucentrosaurus” (though Centrosaurus is now established for the dinosaur).
Note that although the spelling is similar to the stegosaur “Kentrosaurus,” it is a completely different dinosaur.

The Standard Model of the Centrosaurinae

Centrosaurus is the representative genus of the “Centrosaurinae” subfamily.
It lacks the “long horns above the eyes” seen in Triceratops (Chasmosaurinae), and instead has a developed “long single horn on the nose.”

A “long single horn on the nose” is developed

Nasal Horn

Individual variation is significant; it can curve forward or backward, or stand upright.

Frill

It is relatively short, with hook-like projections (hooks) on the rear curving towards the face.

These are believed to have functioned as displays to peers or “fashion” for species identification.
Their body shape was thick like a barrel, with a stable structure and a low center of gravity.

Alberta’s Bone Beds: A “Wildebeest-like Life” of 10,000

From “Dinosaur Provincial Park” in Alberta, Canada, fossils are discovered in such vast quantities that even if paleontologists from all over the world gathered, they couldn’t dig them all up.

Massive Herds Lost to Muddy Streams

“Bone beds,” where bones are concentrated in specific locations, contain the remains of thousands to ten thousand individuals.
The cause of death is considered to be mass drowning due to “river flooding,” rather than carnivorous dinosaurs or disease.

They migrated seasonally in massive herds, much like modern African wildebeests.
While crossing rivers, they were caught in floods, and the entire herd was swallowed by the muddy stream.
This tragic record is irrefutable evidence that they were highly social animals.

Evolutionary Mysteries and Records of Disease

Horn Evolution and the “Peaceful Resolution” Theory

There is an interesting hypothesis regarding the evolution of the Centrosaurinae.
The theory suggests they evolved from the sharp-horned Centrosaurus to “Achelousaurus” with stump-like horns, and then to “Pachyrhinosaurus” with a massive boss (bump).

Sharp horns carry the risk of inflicting fatal injuries in fights between the same species.
Therefore, it is thought that by evolving into a “boss” used for head-butting matches, they avoided unnecessary killing and ensured the prosperity of the species.

Dinosaurs Also Suffered from Disease

Thanks to the vast number of fossil samples, traces of healed fractures and osteosarcoma (bone cancer) have been found.
Mummified fossils with remaining skin also exist, and their appearance while alive is being revealed in detail.

“Lizard with Large Openings”: Was 80% of the Frill Hollow?

Origin of the Scientific Name

The scientific name “Chasmosaurus” derives from the Greek word “chasma” (meaning large hole or opening), translating to “Opening Lizard” (or “Chasm Lizard”).
Why was it given such a name? One look at its frill—its identity—makes the reason obvious.

Huge “Holes” Occupying Most of the Surface Area

The frill of Chasmosaurus was a massive rectangle reaching over 1 meter in width and 1.5 meters in length, but it was not a “solid shield” like that of Triceratops.
There were gaping openings on the left and right sides; surprisingly, more than 80% of the surface area was hollow (consisting only of a bone frame).

80% of the frill was hollow

The Role of the Massive Frill: Weight Reduction and Display

For what purpose did this massive, hole-filled frill exist?

“Weight Reduction” is Certain

First, “weight reduction” is considered a certainty.
If the entire frill were solid thick bone, it would be too heavy to support with the neck.
By reducing the bone to the absolute limit and opening holes, it is believed they could move nimbly while maintaining a huge ornament.
*In living individuals, these holes were covered by skin and muscle.

The “Display Theory” is the Leading Candidate

Currently, the most dominant theory is that the frill was used as a “billboard (display).”
Blood vessels ran through the skin, and it is possible they flushed blood to change color to intimidate rivals or displayed vivid colors to court the opposite sex.

Defense Theory and the “Defensive Circle”

It was once thought to be a defensive shield, but a frill full of holes is too fragile for physical attacks.
However, in group battles, it may have been a different story.
When attacked by carnivorous dinosaurs, they likely formed a defensive circle like musk oxen, sheltering the children in the center.
It is believed that by facing outward and lining up their massive frills, the adults created a visual “barricade” to intimidate enemies.

The Mystery of the Horns and Herds of 1,000

Horns That Disappear with Growth?

Chasmosaurus possessed three horns on its forehead and nose, but they were not as developed as those of Triceratops.
In recent years, theories such as “supraorbital horns (brow horns) being absorbed and shortened as they grew” or that the differences represent sexual dimorphism (differences between males and females) are being debated.

Bone Beds on a Scale of 1,000

In Alberta, Canada, “bone beds” containing fossils of many individuals gathered in one place have been discovered.
These are traces of entire herds being washed away by floods, suggesting that Chasmosaurus formed massive groups, sometimes reaching up to 1,000 individuals, and lived with a high degree of sociality.

Fossil “Children” That Thrilled Researchers

Chasmosaurus is one of the most thoroughly researched ceratopsians.
The reason lies in the “quality” and “quantity” of the fossils.

Skin and the Discovery of Juveniles

Many high-quality fossils exist, including “skin fossils” with scale impressions.
Furthermore, what delighted researchers was the excavation of multiple well-preserved “child fossils (juveniles).”
It is rare for the fragile bones of juveniles to remain, and this provided valuable clues for understanding changes in body shape (such as head-to-body balance) associated with growth.

Taxonomic Changes and Museums in Japan

Consolidation from 10 Species to 2

In the past, due to individual differences and growth stages, fossils were often classified as separate species, and it was said that over 10 species existed.
Currently, classification has been organized, and the following two are considered the main valid species.

Chasmosaurus belli

Has short supraorbital horns.

Chasmosaurus russelli

A primitive species with supraorbital horns.

Exhibitions in Japan

You can see reconstructed skeletons in Japanese museums, but names may change due to shifts in classification.
For example, a skeleton once labeled as “a species of Chasmosaurus” at the Fukui Prefectural Dinosaur Museum is now considered highly likely to be “Albertaceratops” or “Medusaceratops.” Information is constantly updated alongside research.

“Dragon King of Hogwarts”: A Name Inspired by Harry Potter

“Dragon Bones” That Surprised Even Paleontologists

The fossil of Dracorex was first discovered in 2003 in South Dakota, USA.
Upon seeing the discovered skull, renowned paleontologist Robert Bakker was reportedly astounded by its dragon-like shape and exclaimed, “This is a dragon’s bone!”

Meaning and Origin of the Scientific Name

When formally described in 2006, this dinosaur was given a very unique scientific name:
“Dracorex hogwartsia.”

• Draco: Latin for “Dragon”
• Rex: Latin for “King”
• Hogwartsia: Derived from “Hogwarts School of Witchcraft and Wizardry” in the Harry Potter novel series

In other words, the name means “Dragon King of Hogwarts.”
Thanks to this witty naming and its visuals resembling a fantasy creature, Dracorex instantly captured the hearts of dinosaur fans.

A Shocking Theory: “Does Dracorex Not Exist?”

However, a few years after its discovery, paleontologist Jack Horner, known for supervising the movie Jurassic Park, announced a shocking hypothesis that overturned the existence of this “Dragon King.”

The theory was that “an independent species called Dracorex does not exist; it is merely a juvenile (child) Pachycephalosaurus.”

Basis for the Suspicion

Unlike Pachycephalosaurus, famous as the “bone-headed dinosaur” with a domed skull, Dracorex has a flat head with no dome.
At a glance, they look like different species, but detailed analysis pointed out the following:

All Fossils are “Children”

Dracorex fossils are small in size, indicating a high possibility that they are growing juveniles.

Matching Parts

When comparing the skeleton with Pachycephalosaurus and Stygimoloch from the same era, characteristics other than the horns and dome match perfectly.

From this, a new diagram of “a dinosaur that changes its appearance dramatically as it grows” emerged.

From Dracorex to Pachycephalosaurus: A Dramatic Transformation

Jack Horner’s theory is now well-established, and the three dinosaurs once thought to be independent species are now believed to be different growth stages of a single species, “Pachycephalosaurus.”

If likened to humans, the growth stages are as follows:

Early Teens (Juvenile) = Dracorex

The period when the head is flat, but the horns on the back of the head are growing long and sharp.
This appearance was mistaken for a “dragon.”

Late Teens (Sub-adult) = Stygimoloch

The period when the dome on the top of the head begins to swell, but the horns on the back of the head still remain long.
It used to be called the independent species “Stygimoloch.”

Adult = Pachycephalosaurus

The dome on the head fully grows and becomes massive.
As a trade-off, the horns on the back of the head are absorbed, becoming shorter and rounder.

In short, Dracorex was essentially a nickname given to “Pachycephalosaurus during its childhood.”

Value Remains Even as an Illusion: A Carnivorous Childhood?

As an independent species, “Dracorex” is destined to disappear from taxonomy.
However, its discovery provided extremely valuable evidence.

Detailed examination of the Dracorex skull revealed that sharp triangular teeth resembling those of theropods (carnivorous dinosaurs) grew in the front of the jaw.

It was revealed that sharp triangular teeth resembling those of theropods (carnivorous dinosaurs) were growing.

While adult Pachycephalosaurus are considered fully herbivorous, during their childhood (the Dracorex phase), they may have been omnivorous, eating insects and small animals to ingest high-nutrition food for rapid body growth.

The name “Dragon King of Hogwarts” may become a phantom in academic terms, but the “story of growth” told by its bones has vividly changed our view of dinosaurs, just like magic.

Discovered in a Native American Sacred Site: Named After the “Buffalo”

A Rare Dinosaur Exclusive to Montana

Fossils of Einiosaurus were discovered in the present-day state of Montana, United States.
To this day, fossils of this dinosaur have only been found in Montana, making it a very regionally specific existence.

Meaning of the Scientific Name: “Buffalo-like Reptile with a Forward-Curving Horn”

Notably, the initial discovery site was within a Native American reservation (a sacred site).
In honor of this discovery location, their language was incorporated into the scientific name.

Einio

Means “buffalo” in the language of the Blackfoot tribe of Native Americans.

In other words, Einiosaurus means “Buffalo Lizard” (or Buffalo-like reptile) in the Blackfoot language.
The scientific name Einiosaurus procurvicornis, formally named in 1995, encompasses the meaning “Buffalo-like reptile with a forward-curving horn,” a name that beautifully fuses its distinctive appearance with local culture.

*Note: However, its actual movements are believed to have been much slower than a buffalo, incapable of running violently.

A Nose Horn Like a “Giant Can Opener” and a Unique Head

While Einiosaurus falls into the somewhat smaller category among ceratopsians, which include giant species, its head possessed a striking individuality.

A “Nose Horn” Curved Like a Reverse Hook

Its greatest feature is the shape of the horn on its nose.
It curled downwards toward the front, drawing a spectacular “reverse hook” arc.
Its shape is described as drooping forward like “melted soft-serve ice cream” or resembling a “giant can opener.”

Described as “melted soft-serve ice cream” or a “giant can opener”

Frill Spikes to Boost Defense

On the frill (neck shield) at the back of its head, there were large curved horns or two long, sharp, thick spikes, which enhanced its rear defense.
The skull itself was about 1.5 meters in size, which was compact compared to similar ceratopsians (which could reach the 3-meter class).

Unsuited for Battle? The Role of the Enigmatic “Curved Horn”

A horn so extremely curved and pointing downwards is clearly unsuitable as a weapon for piercing enemies.
Why it took this shape remains a subject of debate, with the following theories primarily proposed.

Theories Regarding Usage

Foraging Tool Theory

Used to dig up plant roots or rhizomes growing in the ground.

Defense Theory

While the shape was not ideal, it also served to protect against enemies.

Display Theory

Used for species identification or to appeal to the opposite sex (display).

Theories Regarding Formation Factors

Malformation/Mutation Theory

Could it be that an individual with a curved nose was simply born by chance due to a genetic mutation?

Fossil Deformation Theory

Could the fossil itself have been deformed as a result of compression within the geological strata?

In fact, since only one fossil with a well-preserved snout has been discovered so far, the truth remains a mystery.

Evolutionary Missing Link Theory

It was once thought that this unique horn might be a “missing link” showing the process of evolution.
The speculation is that it is an intermediate species where the horn gradually curved forward during the evolution from the nose-horn-developed “Styracosaurus” to “Pachyrhinosaurus,” which possessed a large boss instead of a horn.

Life in “Herds” and Sociality as Told by Bone Beds

Traces of Mass Death by Flood or Drought

Einiosaurus is believed to have lived in “herds” rather than alone.

Believed to have lived in “herds” rather than alone

The basis for this is the bone bed (a dense concentration of bones) at the “Dino Ridge Quarry” in the Two Medicine Formation of Montana.
Here, hundreds of bones representing more than 15 individuals were found at once, suggesting a high possibility that the entire herd perished simultaneously after being caught in some sudden accident or disaster (such as a flood or drought).

Protecting Themselves in Multi-Generational Herds

The discovered fossils included individuals of various ages, indicating that they formed herds containing everything from adults to children.
Ferocious predators such as Daspletosaurus existed in North America at that time.
For the Einiosaurus, which was not fast on its feet, forming herds was likely the best survival strategy to deter attacks from predators.

A Frill Like the “Snake Hair” of the Monster Medusa

The most prominent feature of Medusaceratops’ appearance is the massive, hook-like spikes (hornlets) growing out of the top of its frill.

Origin of the Name “Medusa”

Because these undulating, curved spikes look just like the “snake hair” growing from the head of the monster Medusa in Greek mythology, it was given a genus name meaning “horned face of Medusa.”

The True Role of the Spikes

These flashy spikes were not used for defense (as weapons) against natural predators.
Instead, it is believed they developed for visual display among peers, appealing to mates, or for “individual and species recognition” within a herd.

The “Trickster God Loki” That Baffled Scholars

Due to its peculiar physical traits, Medusaceratops is also a dinosaur that caused years of taxonomic headaches for researchers.

A Taxonomy Shifting Back and Forth

Ceratopsids are broadly divided into the “Chasmosaurus subfamily” (Chasmosaurinae) and the “Centrosaurus subfamily” (Centrosaurinae).
Because this species possessed magnificent brow horns (horns above the eyes), it was initially classified as a chasmosaurine.
However, later detailed analysis revealed that it was actually an “early member of the centrosaurines.”

Confusion With a Close Relative

Furthermore, there was a period when its fossils were confused with those of a very similar horned dinosaur, “Albertaceratops,” which was discovered in the same geological formation.

Established as a New Species in 2010

It wasn’t until 2010 that it was finally recognized as an independent new species through the research of paleontologist Michael Ryan and his team.

The Humor Behind the Specific Name “lokii”

The specific name was given in honor of “Loki,” the trickster god of Norse mythology.
Because its classification was so complex, the name includes the humorous implication that it had “baffled and played tricks on scholars for years,” just like Loki himself.

Medusaceratops: a dinosaur with undulating spikes reminiscent of a Greek monster, that toyed with scholars like a Norse trickster god.
Its unique appearance and complex research history beautifully illustrate the evolutionary diversity of ceratopsians and the profound depths of taxonomy in paleontology.

The Name “Microceratops”—Unnoticed for 50 Years

This dinosaur was once widely known by the name Microceratops.
It was named Microceratops in 1953, but it was later discovered that this scientific name was already in use as a genus name for a wasp.

Because there is a rule that scientific names must be globally unique, this dinosaur has the very unusual story of being renamed Microceratus in 2008.
What makes this story even stranger is that this duplication went completely unnoticed by anyone for over 50 years.

Characteristics as a Primitive Ceratopsian

Microceratus was a primitive ceratopsian, possessing a robust, bird-like beak (snout) and a small neck frill.

Its appearance shares very similar characteristics with Psittacosaurus, which also inhabited the same region.
However, Microceratus lived in a much later era than Psittacosaurus, so it seems the two never met in life.

Discovery and Naming: A New Face in the Dinosaur World Debuting in 2013

It was in 2013 that Nasutoceratops was officially recognized and named as a new species.
While “Sinoceratops,” registered in 2010, is famous as a “rising star” in the ceratopsian world, Nasutoceratops is even more recent—a true “promising newcomer.”

Currently, the recovered fossils are very limited, consisting only of a distinctive skull and parts of the upper arm. However, its unique shape has generated significant anticipation for future research.

Named for Its “Large Nose”: A Unique Facial Structure

The total length of Nasutoceratops is estimated to have been about 4 to 6 meters.
Its scientific name directly reflects its physical characteristics.

Meaning of the Name

“Nasutoceratops” translates to “large-nosed, horned face.”

Nose Characteristics

While its snout was short from front to back, the nasal cavity extended vertically, resulting in a structure where the nose was prominently emphasized.
The nose was rounded like that of Pachyrhinosaurus, suggesting a somewhat primitive physical constitution.

Its Most Defining Feature: Curved Horns Like a “Bull”

Even more eye-catching than its large nose are the unique “horns” growing from its head.

Curved horns resembling a “bull”

Unlike typical ceratopsians, the two horns above the eyes of Nasutoceratops curved strongly outward before pointing forward and upward.
They formed a beautiful arc, resembling the horns of a modern-day “water buffalo.”

Horn Structure

Like water buffalo horns, it is known that they were hollow inside, making them lightweight.

The Mystery of Function

Aside from the theory that this was for weight reduction, there is even a theory that they “served as swim bladders,” but the details remain shrouded in mystery.

Evolutionary Mystery: An Outdated Survivor?

Taxonomically, Nasutoceratops belongs to the Centrosaurinae subfamily, alongside dinosaurs like Styracosaurus.
However, they occupy a somewhat unusual position in the evolutionary history of ceratopsians.

They lived approximately 76 million years ago.
In North America (around Utah) during this era, Centrosaurine ceratopsians were already beginning to disappear, while the Chasmosaurus clan was expanding its influence.
Normally, Centrosaurines of the type with two brow horns and an undeveloped nasal horn should have already been extinct by this time.

Yet, Nasutoceratops popped up in this era.
As the world shifted toward newer types, it is suggested that they survived as “remnants of a primitive species,” maintaining their unique style.

Summary

Making its home in Utah while other ceratopsians underwent repeated evolution and replacement, Nasutoceratops stuck to its unique style of a “large nose” and “bull-like horns.”
Although few fossil parts have been found, its distinct shape and background as an “outdated survivor” continue to attract the interest of many dinosaur fans and researchers.

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.