A Discovery That Rewound Time and Its Unique Features

The Afrovenator fossil was initially thought to be from the Early Cretaceous, but a re-examination of the rock layers corrected its period to the Middle Jurassic.
This was a very important discovery, as it demonstrated the diversity of dinosaurs on the African continent at that time.

Its skeleton is similar to that of a Late Jurassic Allosaurus, but its overall build was more slender and retained more primitive features.
Its skull was low and long, with a narrow, pointed snout.
Its tail was also stiff and the rest of its body was slender.

Hunting Style and Physical Characteristics

The forelimbs of Afrovenator were powerful, and its three sharp claws were a strong weapon for catching and tearing prey.
Its teeth were thin and knife-like, making them well-suited for slicing meat.

However, its hind limbs had a shorter tibia than its femur, so it was likely not a runner type that could run fast for long distances.
Therefore, it is believed to have hunted by ambushing and surprise attacks rather than relentlessly chasing its prey.

North Africa, where Afrovenator lived in the Middle Jurassic, was a rich floodplain with vast rivers.
Fossils of other dinosaurs, such as the sauropod Jobaria and a theropod similar to Suchomimus, have been found in the same rock layers, suggesting that Afrovenator may have preyed on them.

Classification and Close Relatives

Afrovenator is considered a close relative of Dubreuillosaurus and Eustreptospondylus, both discovered in Europe, and some theories suggest that these dinosaurs form a group called “Afrovenatorinae.”

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A Storied History and the Bone Wars

The fossil of Anchisaurus was discovered by a well-digger in 1818.
However, its rarity was not understood at the time, and it was mistakenly thought to be human bones.
It was later identified as a reptile fossil in 1855 and formally named “Anchisaurus” by Othniel Charles Marsh in 1885.

The “Bone Wars” that erupted in North America during this period led to the excavation of many high-quality specimens, which allowed scientists to understand its complete appearance.
However, a complete skeleton has still not been assembled, and its neck and tail have been reconstructed based on other prosauropods.
The fossilized footprints of Anchisaurus were discovered in Connecticut 20 years before it was officially named, confirming its existence in the Early Jurassic period.

The Unique Ecology of a Small Body

Anchisaurus had leaf-shaped teeth that were not suited for attacking animals, and it is believed to have eaten low-lying plants.

Its teeth were leaf-shaped and not suited for attacking animals.

It is also known to have swallowed stones to aid in digestion.

With its small body, it typically moved on four legs, but it is presumed that it sometimes stood on two legs to eat from tree branches.

It sometimes stood on two legs to eat from tree branches.

The thumb on its hand had a sharp claw, but its shape was not suited for attack.
It was also a slow walker and could not run fast enough to escape from carnivorous dinosaurs.

It was a slow walker and couldn’t run fast enough to escape from carnivorous dinosaurs.

However, this small body and unique ecology may have been one of the reasons its lineage was able to thrive as the ancestor of sauropods.

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Size and a Storied History of a Giant Predator

Carcharodontosaurus, which reached lengths of over 13 meters, was comparable to Tyrannosaurus, but is now seen as being slightly smaller.
Nevertheless, the fact that such a massive predator existed some 10 million years before Tyrannosaurus surprised many researchers.

Its discovery was marked by an unfortunate history.
The first fossils were found in the 1920s but were initially mistaken for those of another dinosaur, Megalosaurus.
Although it was finally recognized as a new species in 1931, the valuable specimens discovered up to that point were destroyed in the fire of World War II, leaving its true nature a mystery for many years.

A turning point came in 1995.
A nearly complete skull was discovered in Morocco, and it was found to be over 1.5 meters long.
This skull was one of the largest ever discovered for a carnivorous dinosaur, but it was lighter and narrower than a Tyrannosaurus‘s, making it suitable for swift predatory actions.

Its Role as Africa’s Apex Predator

Carcharodontosaurus fossils have been found throughout North Africa, suggesting that it reigned at the top of the ecosystem over a vast region.

Another massive carnivorous dinosaur, Spinosaurus, also lived on the African continent during the same period.
The renowned German paleontologist Ernst Stromer, who also named Spinosaurus, is known for formally describing Carcharodontosaurus.
The two are thought to have been in competition in the same region, and fossils of Spinosaurus with what appear to be Carcharodontosaurus bite marks have been found.

Although few fossils of its torso have been found, based on the characteristics of its close relative Giganotosaurus, it is predicted to have had short arms, large hind legs, and a long tail.

It is predicted to have had short arms, large hind legs, and a long tail.

The teeth of Carcharodontosaurus were sharply triangular and lacked the significant curve seen in other theropods.
This tooth structure suggests that it was a ferocious predator that efficiently tore through the flesh of its prey.

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“Hollow Form” and a Sleek, Swift Runner

Origin of the Scientific Name

The scientific name Coelophysis means “Hollow Form” in Greek.
True to its name, the interiors of their bones were hollow.
This structure, which dramatically reduced weight while maintaining strength, is a characteristic shared with modern birds and served as a vital weapon for their success as agile hunters.

Physical Characteristics

Its total length was about 3 meters.
About the size of Deinonychus, it possessed an extremely slender physique.

It possessed an extremely slender physique

Using its long neck, tail, and powerful hind legs, it is believed to have been capable of running at speeds of 30 km/h.
Additionally, its forelimbs had three fingers equipped with sharp claws, and with over 100 serrated teeth lining its upper and lower jaws, it never let prey escape.

With over 100 serrated teeth lining its jaws, it never let prey escape

The Miracle of Ghost Ranch and the “Rioarribasaurus Incident”

Mass Death of Over 500 Individuals

In 1947, Edwin Colbert discovered a “bone bed” containing fossils of over 500 Coelophysis individuals at “Ghost Ranch” in New Mexico.
It is speculated that an entire herd was swallowed and deposited by a sudden flood. This became a precious discovery that included individuals of various growth stages, from children to adults.

Controversy Over the Scientific Name

This discovery later triggered a controversy known as the “Rioarribasaurus Incident.”
Suspicions arose that the initially discovered holotype and the Ghost Ranch specimens were different species, and for a time, the new name “Rioarribasaurus” was proposed.
However, a solution was ultimately reached to redesignate the Ghost Ranch specimen as the “neotype,” and the name Coelophysis was preserved.

Alleged “Cannibalism” and True Diet

Juvenile Bones in the Stomach?

The most sensational aspect of the Ghost Ranch discovery was the small bones found in the abdominal region of an adult.
Initially, this was taken as evidence that it “ate its own children (cannibalism),” and for a long time, Coelophysis was featured in illustrated books as a “cruel cannibal dinosaur.”

New Discoveries Clearing Its Name

However, recent reanalysis has overturned this established theory.
It was revealed that the bones in the stomach were not juveniles, but rather early crocodylomorphs such as “Hesperosuchus.”
It was not eating its own kind, but merely preying on small crocodile relatives.
After more than half a century, the stigma of “child killer” was finally cleared.

Actual Diet

Using their sharp teeth and agility, they hunted lizards, mammals, and small crocodylomorphs, while also appearing to have a side as scavengers that scavenged the leftovers of large carnivorous dinosaurs.

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Named After “Oak Trees”? A Paradox with Reality

Meaning of the Scientific Name and the Contradiction

The scientific name Dryosaurus means “Oak Tree Lizard” in Greek.
It is said to be derived from the shape of its teeth resembling oak leaves, or the fact that it lived in forests.

However, there is a botanical paradox here.
It is believed that “oak trees” and their relatives had not yet evolved on Earth during the Jurassic period when they lived.
This dinosaur, which despite its name knew nothing of oak trees, was a small ornithopod (Iguanodon relative) measuring about 3–4 meters in length and weighing 77–90 kg.

Its Only Weapon Was “Speed”! Three-Toed Feet and Evolution

The biggest feature of Dryosaurus is its extremely plain appearance.
It lacked the horns of Triceratops, the armor of Ankylosaurus, or the spikes of Stegosaurus.

Evolved Foot Structure

At first glance, it resembles the primitive Hypsilophodon, but it possesses more evolved characteristics.
While Hypsilophodon had four toes on its hind limbs, Dryosaurus had three, a structure better suited for running.

A “Spring” for Escape

Their only and greatest means of defense was to “run away.”
Examination of the skeleton reveals that the shin bone (tibia) is longer than the thigh bone (femur), a characteristic unique to fast-running animals.
Using its agile body and spring-like legs, it dashed through the forest like the wind.

Run from Allosaurus! A Harsh Environment Full of Giant Dinosaurs

The habitat of Dryosaurus was truly a “den of monsters.”

Giant Rivals

Giant sauropodomorphs like Diplodocus and Brachiosaurus, more than ten times its size, crowded the area.
While being careful not to get trampled by them, they survived by using their beaks to eat low-lying plants left over by giant dinosaurs or tough vegetation.

Ferocious Predators

Furthermore, ferocious large carnivorous dinosaurs like Allosaurus and Ceratosaurus prowled the surroundings.
Weaponless Dryosaurus, especially young individuals, were prime “prey candidates.”
Nevertheless, the large number of fossils discovered tells the story that they thrived as a species even in such a harsh environment.

Were Babies Quadrupedal? The Truth About Growth and Classification

Changes Due to Growth

Although basically bipedal, hatchlings had sturdy forelimbs and may have walked on four legs.
As they grew, their hind limbs developed, likely transforming them into fleet-footed bipedal runners.

Did They Live Worldwide? Changes in Classification

It was once thought that fossils were also found in the UK and Tanzania.
However, recent research has revealed that they are distinct species (the British species is “Valdosaurus” and the Tanzanian species is “Dysalotosaurus”).
Currently, Dryosaurus is established as a species representative of North America.

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A Swift Body and a Unique Evolution

Elaphrosaurus had a long, slender neck, torso, and tail, and its bones were hollow, making it very light.
Its weight was about 200 kg, roughly the same as a modern lion, and this physique is thought to have made it the fastest runner of the dinosaurs during the Jurassic period.

Initially, its slender body led researchers to believe it was a relative of the North American ornithomimids (ostrich dinosaurs).
However, it is now believed to have been a relative of theropods that lived in the Southern Hemisphere, such as Ceratosaurus and Carnotaurus.
This suggests that Elaphrosaurus followed a unique evolutionary path.

A Mysterious Full Appearance

Although fossils of Elaphrosaurus have been discovered, no skull has ever been found.
As a result, its complete appearance remains a mystery.
Some suggest that it was a type of Ceratosaurus, and thus may have had a horn on its nose, but this is not certain.

Elaphrosaurus was a dinosaur shrouded in mystery that ran through the Jurassic period with its lightweight body and speed.

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“Fierce-eyed Dawn Crocodile”: The Intimidating Face Indicated by its Scientific Name

The scientific name “Eocarcharia dinops” holds a very intense meaning that symbolizes the physical characteristics of this dinosaur.

Meaning of the Name

“Fierce-eyed Dawn Crocodile”

Supraorbital Ridges and Display

Why was it given such a name?
The reason lies in the shape of the skull around the eyes.
In the discovered fossils, the part protruding above both eyes like a visor (the brow area) rose significantly high with thicker bone than found in general theropods.
This is believed to have given it an intimidating and ferocious impression, as if it were constantly glaring at its opponents.

Paleontologists such as Paul Sereno and Stephen Brusatte have pointed out that this “supraorbital ridge” (brow ridge) was not merely a decoration but may have been used for combat between individuals of the same species or for courtship (display).
When males butted heads, this thick bone might have served as a weapon while simultaneously acting as a shield to protect their own eyes.

An “Active Hunter” with Shark-like Teeth

A Carnivorous Dinosaur 6 to 8 Meters Long

Eocarcharia was a carnivorous dinosaur with an estimated total length of 6 to 8 meters.
Although smaller compared to its relative Carcharodontosaurus that appeared later, it boasted sufficient size as a predator of its time and occupied a basal position within the family Carcharodontosauridae.

Sharp Teeth Designed to Tear Flesh

Its most defining feature was the “sharp, shark-like teeth” unique to its group.
Lined with thin, sharp teeth featuring serrations on the edges, this structure was suited not for crushing the bones of prey, but for tearing off flesh and causing massive blood loss.
This dental characteristic supports the theory that they were not scavengers feeding on carrion, but “active and powerful hunters” that attacked and brought down prey themselves.

Coexistence Through Skillful “Niche Partitioning” with Rivals

Other large carnivorous dinosaurs have also been found in the region where Eocarcharia lived.
They managed to coexist skillfully in the same environment by practicing “niche partitioning”—targeting different prey and occupying different spaces.

The Active Hunter “Eocarcharia”

An apex predator that utilized its sharp teeth and physical abilities to attack and prey on living herbivorous dinosaurs like Nigersaurus.

The Scavenger “Kryptops”

Abelisauridae.
It avoided competition by acting as a “scavenger,” eating leftovers and carcasses rather than hunting large prey itself.

The Fish-Eating Specialist “Suchomimus”

Spinosauridae.
By preying primarily on “fish” at the water’s edge, it established a status unrelated to the struggle for terrestrial prey.

The “Three-Way” Balance Inherited by the Next Generation

This magnificent division of roles was carried over to later eras (Late Cretaceous Africa).

• Position of Eocarcharia → To Carcharodontosaurus
• Position of Kryptops → To Rugops
• Position of Suchomimus → To Spinosaurus

Even as the actors became gigantic and were replaced, this tripartite balance of hunter, scavenger, and fish-eater continued to be maintained.

The Mystery of the “Chimera” Surrounding the Specimen

Was the “Fierce Eye” from Another Dinosaur?

Eocarcharia is also a dinosaur shrouded in mystery.
No new specimens have been found since its discovery in 2000.
Furthermore, in recent years, it has been identified that part of the skull (around the eye socket) previously considered a characteristic of Eocarcharia actually belonged to a member of the Spinosauridae (likely Suchomimus) living in the same era.

If this observation is correct, the skull information we have for Eocarcharia might be a “chimera”—a reconstruction mixing fossils from multiple dinosaurs.
Even the characteristic of the “fierce eye,” which inspired its scientific name, might have actually been a misidentification of parts from another dinosaur.

While its true form remains in the mist, the fact that they played an important role in Early Cretaceous Niger remains unchanged.
Eocarcharia is a valuable existence that teaches us both the complexity of ancient ecosystems and the difficulties of fossil research.

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True to the Name “Dawn Runner”! Speedy Feet Specialized for Escape

Origin and Meaning of the Name

The scientific name “Eocursor” carries the meaning “Dawn Runner.”
True to its name, they possessed high physical abilities specialized for running.

Long Shin Bones = Proof of High-Speed Running

A characteristic of the discovered fossils is that the shin bones are longer than the femurs (thigh bones).
Biologically speaking, this leg structure indicates suitability for high-speed running.

At that time, the best defense for Eocursor against predators like carnivores was not to fight.
It is believed that their survival strategy was to use their long legs to run away at high speeds.

Iguana-like Teeth and Herbivorous Ecology

Leaf-shaped Teeth

Its mouth was lined with “leaf-shaped” teeth.
These teeth closely resemble those of the modern green iguana, telling us that they were adapted to eat plants efficiently.

A small herbivorous dinosaur with iguana-like teeth, dashing like the wind across the land over 200 million years ago.
That is the true image of Eocursor.

The Roots of Ornithopods? An Important Taxonomic Position

Regarding classification, there is a theory that it is not a true ornithopod, but as an early dinosaur, it is certainly positioned close to the evolutionary roots of ornithopods.
Eocursor is positioned as a crucial entity for understanding the origins of the ornithopods that flourished in later eras (such as Iguanodon and Hadrosaurus).

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An “Old Timer” with a History Longer than Tyrannosaurus

The 1863 Discovery and the Bizarre Scarcity of Fossils

The discovery of this dinosaur dates back to 1863, approximately 200 years ago.
This predates the discovery of the famous Tyrannosaurus (1892), making it a historic figure—effectively a “veteran”—in the field of paleontology.

However, despite this long history, the number of excavated bones remains strangely low to this day, consisting only of limb bones and vertebrae.

Name Recognition in Japan: Countable on Two Hands?

An old discovery, yet few fossils.
Perhaps because of this, it is said to be a very obscure dinosaur that most people in Japan—perhaps only a handful, to be extreme—would not know.
It is a niche existence known only to true enthusiasts.

From Carnivory to Herbivory: Dietary Transition and Evolution

Characteristics as an Intermediate Dinosaur

Prosauropods, the group to which Euskelosaurus belongs, are believed to represent an “intermediate” stage where dinosaurs transitioned from meat-eating to plant-eating.
In fact, the teeth of Euskelosaurus were shaped to handle both animal and plant matter efficiently.

A Body Too Large for Hunting

While the shape of their teeth suggested potential omnivory, their bodies were likely too large to actively attack and hunt prey.
Therefore, it appears they lived primarily on a diet of plants.

“Curved Femur” to Support Large Digestive Organs

A distinct physical characteristic is that the femur (thigh bone) curves outward from the torso.
This is hypothesized to be due to reasons specific to herbivores.

Because plants take longer to digest than meat, a longer intestinal tract is required.
The curvature of the femur may be an evolutionary adaptation of the skeleton to accommodate the massive digestive system needed to process and absorb plant matter within the abdomen.

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“Fabre’s Lizard”: Dedicated to an Entomologist

Origin of a Rare Name

The scientific name Fabrosaurus was coined in 1964 by French paleontologist Leonard Ginsburg.
The name is derived from the French naturalist and entomologist Jean-Henri Fabre.
It literally translates to “Fabre’s Lizard,” and is known as a very rare case where a dinosaur is named after an entomologist.

Scanty Fossils

The fossil that served as the basis for this name was extremely fragmentary, consisting only of a part of a “lower jawbone” equipped with a few teeth.
This fact is the trigger for the potential “disappearance of the name” described below.

The Biggest Mystery: Is It the Same Dinosaur as Lesothosaurus?

One cannot discuss Fabrosaurus without addressing its relationship with “Lesothosaurus,” which lived in the same region (such as Lesotho) at the same time.

Two of a Kind

The two are extremely similar in appearance and ecological characteristics.
However, while Fabrosaurus fossils are fragmentary, Lesothosaurus is known from the discovery of numerous well-preserved fossils.

Possibility of the Name Disappearing

Currently, many researchers believe that “Fabrosaurus and Lesothosaurus may actually be the same dinosaur (synonyms).”
This is because the Fabrosaurus fossil is too poor to fully prove unique characteristics.
If they are determined to be the same species, the name “Lesothosaurus,” which has better specimens, may take precedence, and the name Fabrosaurus could disappear as a nomen dubium (doubtful name).

Human Child Size! A Runner with “Mammal-like Legs”

Although they are in a taxonomic crisis, their physical abilities were excellent and specialized for their environment.

Agile Escape Artist

It was about 1 meter in length and weighed approximately 18 kg.
Standing only about as tall as a human child, its bones were hollow to reduce weight.
Carnivorous dinosaurs like Megapnosaurus existed in Africa at that time, but since Fabrosaurus had no weapons, it protected itself solely by “running away.”

Distinctive Leg Structure

Bipedal in nature, their hind limbs did not splay out to the sides like reptiles, but extended vertically beneath the torso like mammals.
It is believed that they sprinted at considerable speeds by utilizing this efficient running structure, along with spring-like long hind legs and a tail used for balance.

Primitive Ornithischian: No Cheeks and Poor at Chewing

Fabrosaurus belongs to an extremely early group of Ornithischia (herbivorous dinosaurs), which would prosper in later eras.

No Cheeks

Unlike later dinosaurs such as the duck-billed dinosaurs, they did not have developed “cheeks” to hold plants in their mouths.

Simple Teeth

They possessed only small, pointed, simple teeth and could only move their jaws up and down to “slice” vegetation.

They seemingly adopted a simple eating style of biting off plants growing on the ground and swallowing them whole.

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