Pterosaurs are a group of reptiles that lived during the same era as the dinosaurs and possessed the ability to fly.
They are closely related to dinosaurs and are classified as part of the larger group known as Archosauria.

While we tend to imagine gigantic creatures walking on the ground when we hear the word “dinosaur,” the Earth at that time was also home to pterosaurs that dominated the skies.

Representative Pterosaurs and Their Astonishing Characteristics

Here are some of the most well-known and representative species from the diverse array of pterosaurs.

Pteranodon

Pteranodon

It is one of the most famous pterosaurs in movies and encyclopedias.
With a body that reached nearly 10 meters when its wings were spread, it commanded an overwhelming presence in the skies of its time.

Details on Pteranodon here

Quetzalcoatlus

Quetzalcoatlus

Considered the largest flying animal in history, its wingspan is estimated to have exceeded 10 meters.
This scale, comparable to a modern small aircraft, speaks to the dynamism of ancient Earth.

Details on Quetzalcoatlus here

Eudimorphodon

Eudimorphodon

It was a relatively small pterosaur, characterized by a very long tail, which was reminiscent of a demon.
Flying creatures with such long tails are not seen in the modern world.

Details on Eudimorphodon here

Pterosaurs as Superior Hunters

Pterosaurs survived for a long period, from the Jurassic to the Late Cretaceous.
It is believed that they were not merely creatures that flew, but highly capable hunters with excellent flying and predatory skills.

Although dinosaurs and pterosaurs took different paths in their evolution, both are fascinating ancient creatures that left a spectacular legacy on Earth’s history.

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Have you ever heard the term “marine dinosaur”?
In reality, dinosaurs primarily inhabited the land, and animals generally thought to be in the sea are classified as marine reptiles.
These are creatures specialized for the sea that flourished in the same era as dinosaurs.

These marine reptiles are divided into several groups.

Ichthyosaurs

Possessing streamlined bodies similar to modern fish and dolphins, they were adept at swimming quickly.
Fossils of Utatsusaurus have also been found in Miyagi Prefecture, Japan.

Utatsusaurus

Plesiosaurs

There were types with long necks (such as Elasmosaurus) and

Elasmosaurus

types with short necks (such as Liopleurodon).

Liopleurodon

The long neck is thought to have been useful for catching fish.
Futabasaurus, discovered in Iwaki City, Fukushima Prefecture, is a representative species of this group.

Futabasaurus

Lepidosaurs

While they are thought to have lived on land as well, some species in this group adapted to the sea.

Crocodilians

There were also marine species with heads resembling crocodiles, such as Metriorhynchus, which is an ancestor of modern crocodiles.

Metriorhynchus

Turtles

The giant Archelon, despite existing millions of years ago, had an appearance surprisingly similar to modern sea turtles.

Summary

During the age of dinosaurs, these marine reptiles lived in the vast oceans.
Their existence, having undergone evolution different from terrestrial dinosaurs, tells the story of the diversity of life on the ancient Earth.

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Ornithopoda is a group of herbivorous dinosaurs belonging to the order Ornithischia, represented by famous species such as Iguanodon and Parasaurolophus.
Appearing in the Early Jurassic of the Mesozoic Era, they distributed across almost the entire world, including Antarctica, and flourished greatly until the mass extinction at the end of the Cretaceous.

Distributed across almost the entire world, they flourished greatly.

Ornithopods are known as one of the most successful groups of herbivorous dinosaurs throughout the dinosaur era.

Characteristics and Evolution: Diversity as the Key to Success

Diversity in characteristics and evolution

Due to their high adaptability, ornithopods ranged in size from small species of about 1 meter in length to large species exceeding 10 meters, such as those in the Hadrosaurus family (duck-billed dinosaurs).

Locomotion Style

They were characterized primarily by bipedalism, but larger species could switch between bipedal and quadrupedal walking, using four legs to support their weight.

Diet

Possessing a beak at the tip of their mouths and developed teeth (such as dental batteries), they could grind food finely, allowing them to eat even tough plants efficiently.

Evolutionary Diversity

Ornithopods adapted to a wide range of regions and eras, becoming one of the most widespread dinosaur groups in Earth’s history.

Historical Confusion Surrounding Classification

Because the trait of bipedalism was ancestral to all ornithischians, the group Ornithopoda historically became a “wastebasket taxon” where early species of other groups, such as the Lesothosaurus family and primitive thyreophorans, were mistakenly included.
However, with scientific advancements, species classification has been refined, and their diverse evolutionary paths are becoming clearer.

The post The Bird-Footed Dinosaurs: Ornithopods—A Worldwide Success Story of Astonishing Diversity and Survival. first appeared on 恐竜大百科.

Thyreophorans are a group of ornithischian dinosaurs clad in armor ranging from small to super-sized, inhabiting all continents from the Early Jurassic to the end of the dinosaur era.
As their name implies (meaning “shield bearers”), their most distinctive feature was the armor-like osteoderms (bony plates) that covered their entire bodies.

Thyreophorans are a group of defense specialists composed mainly of stegosaurs (such as Stegosaurus) and

Stegosaurs (such as Stegosaurus)

ankylosaurs (such as Ankylosaurus), whose bodies were covered in armor.

Ankylosaurs (such as Ankylosaurus)

Characteristics of Thyreophorans: Defense and Survival Strategies

Thyreophorans survived the dinosaur era with their heavy armor and unique body structures.

Full-Body Armor (Osteoderms)

All thyreophorans possessed armor-like osteoderms covering their bodies.
Early species had simple scale-like osteoderms, but more evolved species developed elaborate armor such as tail clubs or structures resembling bulletproof vests.
In some species, even the area under the throat was densely covered with osteoderms.

Diet and Locomotion

All were herbivorous, and relative to their body size, their heads were comparatively small and robustly built.
Early species were bipedal, but as carnivorous dinosaurs grew larger, thyreophorans also increased in size and shifted to quadrupedal locomotion to support their weight.

Growth Rate and Habitat

Compared to most other dinosaurs, their growth rate is considered to have been relatively slow.
They adapted to a wide range of environments, from deserts to humid forests.

Unraveling the Mystery: History of Discovery and Research

The history of thyreophorans is long, having been studied even before the word “dinosaur” was coined.

Early Discoveries in Europe

The oldest thyreophoran fossil is Hylaeosaurus, discovered in the UK in 1832.

Hylaeosaurus

Hylaeosaurus was one of the animals, along with Iguanodon and Megalosaurus, cited by Richard Owen as the basis when he proposed the classification group “Dinosauria” in 1842.
However, the discovery of Hylaeosaurus was extremely incomplete.

Around 1874, extensive fossils of a large herbivore clearly equipped with spikes were discovered in the UK, marking the beginning of full-scale research into stegosaurs.

The Full Picture of Stegosaurs and Ankylosaurs

The discovery of more complete fossils accelerated entering the 20th century.

For ankylosaurs (Ankylosaurus family), complete fossils began to be discovered in Asia and North America after World War II, allowing for more accurate identification of their appearance.

In the 1980s, Minmi, the first ankylosaur from the Australian continent, and

Minmi

Antarctopelta, the first ankylosaur from Antarctica, were discovered.

Antarctopelta

From the 1990s onward, fossils of basal thyreophorans important for evolutionary history (such as Scelidosaurus and Scutellosaurus) were discovered in various parts of the world, including China and North Africa, revealing the full picture of their diverse classification.

Scelidosaurus

Scutellosaurus

The post The Moving Fortresses of the Dinosaur World: Thyreophorans—An Evolutionary History Protected by Armor and Spikes. first appeared on 恐竜大百科.

Marginocephalians are a group of dinosaurs belonging to the Ornithischia (Bird-Hipped) lineage, and their name means “fringed heads” or “creatures with decorated margins around the head.”
As the name suggests, their primary characteristic is that the back of the head projected like a frill, with horns and knobs lining the perimeter and face.
This group includes the Ceratopsians (horned dinosaurs), which later flourished greatly, and the Pachycephalosaurs (dome-headed dinosaurs).

Characteristics and Classification: Head Ornaments Are Key

All Marginocephalians were herbivorous, sharing the common feature of specialized head ornamentation.
They are also characterized by having bony projections on their cheeks and a different pelvic shape from other ornithischians.
This group is mainly composed of the following two types:

1. Ceratopsians: Defense Specialists with Horns and Frills

Characteristics

This group is typified by Triceratops, and features large horns on the face and nose, with a significant frill-like structure projecting from the back of the head.

They had horns on their face and nose, and a large frill-like structure protruding from the back of the head.

Many new species have been discovered recently, showing that they underwent an evolution that included a greater variety of skull decorations than previously thought.

2. Pachycephalosaurs: The Group with Dome-Shaped Skulls

Characteristics

This group is represented by Pachycephalosaurus, and is characterized by a thick, dome-shaped skull.

They had a thick, dome-shaped skull.

This solid block of bone is thought to have been used for defense against carnivorous dinosaurs or for display among their own kind.

Evolution and History of Success

The oldest species of Marginocephalians had already appeared by the Late Jurassic period, but they were not prominent at that time.

Early Features and Territorial Expansion

Some early Pachycephalosaurs and Ceratopsians primarily walked bipedally, but most Ceratopsians later shifted to quadrupedal locomotion.
Their diet was mainly herbivorous, though some research suggests certain species may have been omnivorous with a strong tendency toward plant-eating.

They gradually expanded their dominance during the Early Cretaceous, and by the Late Cretaceous, they flourished greatly in the Northern Hemisphere (Laurasia).
The North American Ceratopsians, in particular, grew larger and diversified, developing various forms of horns and neck frills.

The Southern Hemisphere Mystery

In the Southern Hemisphere (Gondwana), fossil evidence is scarce, and little is known about their presence there.

Marginocephalians were a dinosaur group that flourished in the Late Cretaceous of the Northern Hemisphere, using their showy head ornaments as both weapons and display features.

The post The Dinosaurs That Decorated Their Heads: Marginocephalians—Uncovering the Evolutionary Secrets of Horns and Frills. first appeared on 恐竜大百科.

Are you aware that there are three major groups of dinosaurs?
They are the Theropods, which include Tyrannosaurus; the Sauropodomorphs, which include Apatosaurus; and the Ornithischians, to which everyone’s favorites, Triceratops and Stegosaurus, belong.
In this article, we will focus on the Ornithischians, providing a clear explanation of their characteristics, representative dinosaurs, and surprising evolutionary history.

The “Bird-like Pelvis” That Defines Ornithischia

The defining feature of Ornithischia is the shape of their pelvis, which is the same as that of birds (the pubis bone projects backward), and is the origin of the group’s name (“Bird-Hipped”).
This unique pelvic shape has led to their classification as Ornithischia.
This group includes several subgroups of herbivorous dinosaurs, such as:

• Stegosaurs (Stegosaurus, etc.)
• Ankylosaurs (Ankylosaurus, etc.)
• Ceratopsians (Triceratops, etc.)
• Pachycephalosaurs (Pachycephalosaurus, etc.)
• Ornithopods (Iguanodon, etc.)

Ecology and Defense Mechanisms Unique to Herbivores

Since most Ornithischians were herbivores, they had large intestines to efficiently digest plant matter.
As a result, their pubis bones were relatively small and their leg muscles were less developed compared to theropods.

Bipedal ornithischians (such as some ornithopods and pachycephalosaurs) may not have been as fast runners as theropods of the same size.
However, most ornithischians were quadrupedal and possessed powerful armor for self-defense against carnivorous dinosaurs.

For example, Ankylosaurs had hard armor covering their entire bodies, while Stegosaurs, represented by Stegosaurus, used the plates on their backs and tail spikes as weapons.

Stegosaurus

Thanks to these robust defenses and offensive means, they were not easily preyed upon, even by large carnivorous dinosaurs.

The Surprising Truth: Ornithischians Are Not the Ancestors of Birds

Because of the name “Ornithischia” (Bird-Hipped), it is often mistakenly assumed that they were the ancestors of birds, but this is actually incorrect.
The latest research shows that the ancestors of birds belong to the other major group, the Theropods, within Saurischia (Lizard-Hipped).

One of the oldest known ornithischians is Heterodontosaurus, which lived in the Early Jurassic period, about 200 million years ago.

The world of dinosaurs still holds many unresolved mysteries.
Learning the history of unique groups like Ornithischia may deepen your interest in these ancient creatures.

The post What Are Ornithischians? Unveiling Key Species and Surprising Truths About One of the Three Major Dinosaur Groups. first appeared on 恐竜大百科.

Sauropodomorpha is the group of dinosaurs characterized by a long neck and a small head relative to the body, represented by Brachiosaurus and Diplodocus.
They appeared in South America during the Late Triassic period and flourished across vast regions of the Earth from the Early Jurassic to the end of the Cretaceous.
This group is known for including the largest land animals in the history of our planet.

The Truth About the Two Groups that Constitute Sauropodomorpha

In their evolutionary process, Sauropodomorpha consisted of two major groups: Prosauropods and Sauropods.
While it was once thought that “prosauropods evolved into sauropods,” the prevailing theory today is that “both groups split from the same common ancestor.”

1. Prosauropods: Pioneers of Prosperity

Characteristics

This group includes species like Plateosaurus and lived from the Triassic to the Early Jurassic.

Plateosaurus

Many species were only a few meters long and are thought to have been bipedal or facultatively quadrupedal, with omnivorous or herbivorous diets.

Primitive Advantage

They succeeded in achieving gigantism early in the dinosaur age and constituted the majority of the dinosaur population at the time.
They possessed primitive, superior characteristics not seen in later sauropods, such as serrated teeth, sharp hand claws, and grasping fingers.

2. Sauropods: The Largest Giants in History

Characteristics

Represented by Brachiosaurus, Diplodocus, and Argentinosaurus, this group flourished greatly from the Jurassic to the Cretaceous periods.

Argentinosaurus

All were herbivorous, and they walked on four robust legs to support their colossal bodies.
This group includes the largest land animals ever, sometimes reaching over 30 meters in length.

Characteristics and Evolutionary Secrets of Sauropodomorpha

Sauropodomorphs have captivated many people with their immense size and unique appearance.

1. The Role of the Unusually Long Neck

Their most defining characteristic is their extremely long neck.
This neck allowed them to feed on leaves high up, where no other animal could reach.

It could eat leaves from high positions.

Sauropods, in particular, had even longer necks than the prosauropods.

2. The Secret of the Gigantic Body and Skeleton

The largest creatures to have ever lived on land are all classified as Sauropodomorpha.
Their ancestors were bipedal, but they evolved into a quadrupedal posture to support their colossal size.

It is believed that as they grew to giant proportions, they developed air-filled bones (pneumatic bones), which reduced the burden on their legs and allowed them to support their immense mass.

3. Diet and Classification

All Sauropodomorpha were herbivorous and possessed specialized teeth and digestive systems adapted for eating plants.

They belong to the Saurischia (lizard-hipped) lineage, along with the theropods.
This classification was named for the structure of their pelvis, which resembles that of a lizard.

Through their magnificent appearance and evolutionary history, Sauropodomorphs symbolize the great diversity of the dinosaur age.

The post The Giants of the Dinosaur World: Sauropodomorphs—Unveiling the Evolutionary Secret That Produced Earth’s Largest Creatures. first appeared on 恐竜大百科.

Theropods are a group of dinosaurs belonging to the order Saurischia, characterized by lizard-like pelvises, and are known primarily for being carnivorous.
They are one of the three major dinosaur groups, flourishing across vast regions of the Earth from the Late Triassic, approximately 230 million years ago, to the Late Cretaceous, making them one of the most successful species in history.

Physical Characteristics of the Hunters That Reigned at the Apex of the Dinosaur World

Theropods reigned as apex predators in Earth’s ecosystems from the Jurassic to the Cretaceous.
Their strength and success were based on their unique physical structure.

1. Swift Bipedalism and Powerful Hind Legs

Theropods are characterized by slender bodies and long hind legs, with all species walking on two legs.
Their leg muscles were extremely developed, and many species were capable of running at speeds of over 30 km/h, making them adept at quick movements.

They excelled at quick movements

This agility was a major key in tracking down prey.

2. Powerful Heads and Skeletal Secrets

As seen in representative theropods like Tyrannosaurus and Giganotosaurus, they were armed with massive heads and rows of extremely sharp teeth inside their mouths for tearing apart prey.

Armed with rows of sharp teeth inside their mouths

They also possessed hollow bones that lightened their skeletons. This feature, which enabled their agile movements, was a significant evolutionary secret inherited by later birds.

Evolution and Diversity: Changes in Diet and Development of Intelligence

Theropods were not just giant predators; they underwent surprisingly diverse evolution and expanded their ecological niches.

1. Adaptation to Diverse Diets

Initially, theropods were carnivorous, producing numerous predators that stood at the top of the ecosystem, such as Allosaurus.
However, dietary diversity emerged during their evolution.
By the Cretaceous period, it has been confirmed that herbivorous dinosaurs like Jianchangosaurus had appeared.
By possessing diverse diets, like Oviraptor and Therizinosaurus, they adapted to different environments.

2. Intelligence and Sociality

Intelligence developed in theropods, centering on the lineage that became ancestors to birds.
In particular, the group to which Velociraptor belongs is considered to have had superior brainpower, and it is known that some dinosaurs exhibited social behaviors, such as forming packs to hunt.

Some dinosaurs formed packs to hunt

Evolution into Birds: Pioneers of Feathers

Theropods diversified dramatically by the Late Jurassic, and birds emerged from this evolutionary lineage.

Acquisition of Feathers and Evidence of Evolution

Theropods are also known as the first group of dinosaurs to acquire feathers.
The “Paravians” (or stem-birds), to which Deinonychus and Velociraptor belong, are considered the direct ancestors of modern birds.
The inclusion of early birds like Archaeopteryx also indicates that theropods followed the lineage of birds.

Archaeopteryx

Birds inherited theropod characteristics, such as bipedalism and hollow bones, and having survived the mass extinction at the end of the Cretaceous, they continue to thrive today.

Major Classification Groups and Discoveries in Japan

Theropods are divided into numerous subgroups, including Ceratosaurs, Tetanurans, Coelurosaurs, and Coelophysis-like dinosaurs.
The ultimate descendants of these groups are the birds living today.

Theropod fossils have also been discovered in Japan. In 2013, fossils believed to be from a theropod dating back approximately 85 million years were found in strata in Kuji City, Iwate Prefecture, attracting attention as the first such discovery in the Tohoku region.

Theropods are one of the most successful groups among dinosaurs, and their evolutionary history teaches us about the adaptability of life on Earth and its magnificent evolutionary journey.

The post The Main Architects of Evolution: Theropods—The Most Successful Hunters in History and the Lineage That Evolved into Birds. first appeared on 恐竜大百科.

Dinosaurs are broadly divided into two groups, Saurischians and Ornithischians, based on a decisive characteristic: the shape of their pelvis (hip bone).
This classification is extremely important for understanding the diverse ecology and evolutionary paths of dinosaurs.
While the “saurus” included in dinosaur scientific names means “lizard,” academically, it refers to a specific group of reptiles that evolved a unique upright walking gait.

The Two Pillars of Dinosaur Classification: “Saurischians”

Saurischians are characterized by resembling a lizard’s pelvis, with the pubis pointing diagonally forward and down.
This group includes professional carnivores and the largest giants in history.

1. Theropods: Carnivorous Professionals and Ancestors of Birds

Representative theropod dinosaur ‘Tyrannosaurus’

Characteristics

Popular carnivorous dinosaurs such as Tyrannosaurus, Spinosaurus, and Velociraptor belong to this group, and all species are fundamentally bipedal.

The Secret of Evolution

Theropods evolved into birds in later eras.
In that lineage, the pubis tilted diagonally backward, changing into a shape resembling a bird’s pelvis.
Archaeopteryx is also included in this group.

Dietary Diversity

Most are carnivorous, but in recent years, it has been discovered that there were also herbivorous dinosaurs like Jianchangosaurus, indicating a diversity in diet.

Intelligence

Some species, such as Velociraptor, are known to have possessed high intelligence and exhibited social behaviors, such as hunting in packs.

Representative Theropod Dinosaurs

• Tyrannosaurus
• Velociraptor
• Spinosaurus
• Allosaurus
• Giganotosaurus

2. Sauropodomorphs: The Group with the Largest Bodies in History

Representative sauropodomorph dinosaur ‘Brachiosaurus’

Characteristics

This includes herbivorous dinosaurs that walked on four legs with massive bodies, represented by Brachiosaurus and Argentinosaurus.
It is the group containing the largest land animals in history (exceeding 30 meters in length).

Secrets of the Skeleton

It is thought that because they possessed pneumatic bones (bones with hollows) during the process of becoming gigantic, the burden on their legs was reduced.
The long tail functioned to maintain body balance and also served as a weapon for defense.

Process of Evolution

Ancestral species such as Eoraptor were bipedal, but as they increased in size, quadrupedalism later became the mainstream.

Representative Sauropodomorph Dinosaurs

• Brachiosaurus
• Apatosaurus
• Diplodocus
• Argentinosaurus
• Amargasaurus

The Other Pillar of Dinosaur Classification: “Ornithischians”

Ornithischians are characterized by resembling a bird’s pelvis, with the pubis extending diagonally backward parallel to the ischium.
All dinosaurs belonging to this group are herbivorous and possess extremely diverse appearances.

1. Ornithopods: The Duck-Billed Group

Representative ornithopod dinosaur ‘Iguanodon’

Characteristics

Iguanodon and the Hadrosaurus family (duck-billed dinosaurs: Parasaurolophus, Edmontosaurus, etc.) are representative.
They are characterized by long, flat mouths (beaks) like ducks, and they ground down plants to eat using cheek teeth called dental batteries.

Representative Ornithopod Dinosaurs

• Iguanodon
• Parasaurolophus
• Maiasaura
• Edmontosaurus
• Heterodontosaurus

2. Marginocephalians: The Group Characterized by Head Ornaments

Representative marginocephalian dinosaur ‘Triceratops’

Ceratopsians

Represented by Triceratops, they are characterized by large horns and frills (neck shields).
It is believed that the frills also played a role in protecting the neck from attacks by enemies.

Pachycephalosaurs

Groups such as Pachycephalosaurus possess thick, dome-shaped skulls.

Representative Marginocephalian Dinosaurs

• Triceratops
• Protoceratops
• Pachycephalosaurus
• Styracosaurus
• Stygimoloch

3. Thyreophorans: Defense Specialists with Armor and Spikes

Representative thyreophoran dinosaur ‘Stegosaurus’

Ankylosaurs

Represented by Ankylosaurus, they specialize in defense, possessing features such as a club at the end of the tail.

Stegosaurs

Represented by Stegosaurus, they are characterized by having plate-like bones (plates) on their backs.
It is thought that this armor and plates were used for defense and counter-behavior.

Representative Thyreophoran Dinosaurs

• Stegosaurus
• Ankylosaurus
• Gargoyleosaurus
• Kentrosaurus

Definition of Dinosaurs and Standards for Scientific Names and Classification

While the word “dinosaur” is often thought to refer to giant ancient reptiles in general, academically it is very strict.

1. Academic Definition and Upright Walking

Academically, dinosaurs are defined as “the most recent common ancestor of birds and Triceratops, and all its descendants.”
Put more simply, dinosaurs can be thought of as “reptiles that walk upright.”
For example, crocodiles walk with their joints bent, but dinosaurs possess the decisive characteristic separating them from other reptiles: they do not bend their joints outward but extend their legs straight down.

2. Creatures Easily Mistaken for Dinosaurs

Creatures that do not fit the definition of upright walking are distinguished as “non-dinosaur reptiles.”
Pterosaurs such as Pteranodon are a sister group to dinosaurs, and marine reptiles such as Mosasaurus and Plesiosaurus are not included in dinosaurs.

3. Secrets and Changes in Dinosaur Names

The “saurus” attached to part of dinosaur names is the Greek word for “lizard (reptile).”
Also, dinosaur research is constantly advancing, and previous common knowledge may be overturned.
For example, if fossils thought to be different species are found to be the same, they may be unified under the name given first, and the other name may be revoked.
Additionally, since dinosaur body lengths are estimated values based on fossils, the figures may change with repeated research.

The Truth That “Birds” Are Dinosaur Survivors

Modern birds are direct descendants of dinosaurs that evolved from small theropods.
Current taxonomy states that “birds are dinosaurs (theropods) themselves,” and they are included in the academic definition.
There are approximately 10,000 species of living birds, widely distributed around the world—more diverse than us mammals (just under 5,000 species).
Seeing the prosperity of these birds, it can be said that the history of dinosaurs is still continuing.

The post The Complete Guide to Dinosaur Classification! Differences Between Saurischians and Ornithischians and Major Species Explained first appeared on 恐竜大百科.