The Classification of Dinosaurs: Major Groups and Types

Some dinosaurs beside the pool

Source by: American Post

The history of prehistoric animals like dinosaurs is full of interesting facts and valuable information about their classification, habits, and characteristics. Despite their extinction millions of years ago, these predators still attract historians, paleontologists, and academics across the globe.

To help the readers know how dinosaurs are classified, this article has described major groups, subgroups, and types of dinosaurs with pictures categorized according to their body structure, their relationships to each other, and skeletal features.

So, let’s find out how are dinosaurs classified and subgroups.

Saurischia

The classification of dinosaurs

Source by: Phys.org

Temporal Range: 233.23 million years
Kingdom: Animalia
Phylum: Chordata

Saurischians (meaning lizard hip) dominated the planet during the Late Triassic era. The arrangement of their pelvis bones was similar to that of lizards and modern crocodiles, which also have a triradiate pattern.

Their three-pronged pelvic structure distinguished them from the ornithischians who had a four-pronged pelvic structure. The hip structure of saurischians is still found in various reptiles like lizards.

Order Saurischia is further divided into two distinct suborders: Theropoda and Sauropodomorpha. The former comprised carnivorous dinosaurs while the latter included herbivorous and prosauropods dinosaurs.

1. Theropoda

Cladogram of theropoda dinosaurs

Source by: VectorStock

Temporal Range: 231.4 million years
Kingdom: Animalia
Phylum: Chordata
Height: 5 m
Length: 15 m
Mass: 5500 kg

Theropods are known for their three-toed gigantic limbs and hollow bones. Although most of them were carnivorous, some groups also became herbivores, omnivores, and insectivores. Today, over 10,500 living species represent theropods.

Different types of dinosaurs from the Theropoda suborder had distinct skin texture and covering. Smaller species had feather-like structures while the larger ones had bumpy scales on their skin.

Moreover, theropods used their sharp teeth with serrated edges to slash their prey into pieces. Theropods are further divided into two infraorder: Ceratosauria and Tetanurae.

(i) Ceratosauria

Ceratosauria information comparing with human beings

Source by: DeviantArt

Temporal Range: 199.3–66 million years
Kingdom: Animalia
Phylum: Chordata
Height: 8.5 m
Length: 5.3 m to 7 m
Mass: 520 kg

Ceratosaurs were a group of small and medium to large dinosaurs ranged from Late Triassic to Late Jurassic time. With a few exceptions, they were moderately large and known for their robust skull with increased ornamentation.

Their diet included fish and other aquatic creatures. Due to their shortened skull, ceratosaurs used to hunt small prey with a relatively weak bite. Common examples of ceratosaurs are Coelophysis, Syntarsus, and Ceratosaurus.

(ii) Tetanurae

The feature of tetanurae

Source by: Encyclopedia Britannica

Temporal Range: 201 million years
Kingdom: Animalia
Phylum: Chordata
Height: 1.7 to 3 m
Length: 3 m to 9 m
Mass: 907 kg

Tetanurans are closely related to birds due to having a sophisticated air-sac-ventilated lung system. Besides, these dinosaurs had an advanced circulatory system, stiffened tails, a strap-like scapula, maxillary teeth anterior to the orbit, and maxillary fenestrae.

Tetanurae group includes different types of dinosaurs with names such as allosauroids, maniraptorans, megalosaurus, and ornithomimosaurs.

2. Sauropodomorpha

A group of sauropodomorpha dinosaurs in a dark background

Source by: DeviantArt

Temporal Range: 231.4–66 million years
Kingdom: Animalia
Phylum: Chordata
Height: 7 to 12 m
Length: 1.5 m to 40 m
Mass: 60,000–100,000 kg

Sauropodomorphs were long-necked and lizard-footed herbivorous dinosaurs with long tails and gigantic sizes. They are known to be the largest animals to ever walk on the earth during the Mesozoic Era.

Some of the key features of sauropodomorphs include the presence of short hind limbs, large nares, three or more sacral vertebrae, and elongated 10 cervical vertebrae.

Moreover, they had thin spatula-like teeth along with bladed and serrated crowns that helped them in hunting and fighting against enemies.

Given below are various types of dinosaurs pictures belonging to the Sauropodomorpha group.

(i) Prosauropoda

The fossils of the prosauropoda dinosaur

Source by: Wikipedia

Temporal Range: 225–209 million years
Kingdom: Animalia
Phylum: Chordata
Height: 1.1 to 3 m
Length: 6 m to 7 m
Mass: 1500 kg

Prosauropoda includes a group of early herbivorous dinosaurs that dominated other herbivores in their environment. They had a long neck, a small head, and short forelimbs.

Besides, a large claw was used for defense against the enemies. Similarly, prosauropods had small and relatively weak teeth with marginal serrations that allowed them to grind and chew tough fauna.

(ii) Sauropoda

The fossil of a sauropoda dinosaur

Source by: Wikipedia

Temporal Range: 215–66 million years
Kingdom: Animalia
Phylum: Chordata
Height: 6 to 22 m
Length: 5 m to 48 m
Mass: up to 80,000 kg

Sauropods were long-necked and small-headed dinosaurs with long tails and four pillar-like legs. Among all types of dinosaurs, sauropods are famous for their enormous sizes and are known to be the largest animals on the earth.

Besides, they had a system of air sacs for inhaling enough oxygen by allowing a single-direction airflow through stiff lungs. Likewise, their hollow bones reduced the overall weight of their massive necks, which were over 6 times longer than those of giraffes.

The bony osteoderms on their bodies and small clubs on their tails were used as armor.

Ornithischia

The classification of ornithischiad

Source by: Chegg

Temporal Range: 200.91–66 million years
Kingdom: Animalia
Phylum: Chordata

Ornithischians (meaning bird hip) were herbivorous dinosaurs known for their rectangular or tetraradiate pelvis structure similar to that of birds.

Their herds were segregated by age group as juveniles used to prefer living in separate flocks from adults. Some of the animals in this order had filamentous pelts and primitive feathers as well as a toothless mouth covered by a horny beak.

Well-known anatomical adaptations of ornithischians include armored dinosaurs and horn-faced dinosaurs, and it is classified into two suborders: Cerapoda and Thyreophora.

1. Cerapoda

Two cerapoda dinosaurs on the ground

Source by: World Atlas

Temporal Range: 163–66 million years
Kingdom: Animalia
Phylum: Chordata
Height: Undefined
Length: Undefined
Mass: Undefined

Cerapodians are known as horned feet dinosaurs due to their resemblance with Ceratopsia and Ornithopoda. Although they did not have horned feet, they are called so due to their enameled teeth covered by a thicker layer of enamel on the lower side.

They used the sharp edges of their uneven teeth to break tougher plants into pieces. Cerapoda is further classified into three suborders: Pachycephalosauria, Ornithopoda, and Ceratopsia.

(i) Pachycephalosauria

The fossils of the pachycephalosauria dinosaurs

Source by: Wikipedia

Temporal Range: 140–66 million years
Kingdom: Animalia
Phylum: Chordata
Height: 2 m
Length: 2 m to 5 m
Mass: 450 kg

Pachycephalosaurians (meaning thick-headed lizards) were herbivorous and omnivorous dinosaurs predating the Late Cretaceous Period. They had heavily ossified thick skulls in a variety of shapes like flat, domed, or wedged. Dome-shaped skulls were surrounded by spikes or nodes depending on the species.

Other features of pachycephalosaurs are short forelimbs, a heavy tail, a bulky torso with broad hips, and a short neck. Besides, they had good vision, thanks to their large optic nerve.

Similarly, their large olfactory lobes gave them a good sense of smell. To date, paleontologists could not discover complete skeletons of these animals.

(ii) Ornithopoda

The pictures of some ornithopoda dinosaurs

Source by: DeviantArt

Temporal Range: 163–66 million years
Kingdom: Animalia
Phylum: Chordata
Height: 15 m to 30 m
Length: 1 m to 6 m
Mass: 22,680 kg

Ornithopods (meaning bird feet) started as small running gazers and gradually grew in their size. Being the dominant herbivores of the North American landscape, these predators have developed the most sophisticated chewing apparatus similar to that of modern mammals like cows.

Once they reached their ecological dominance, Cretaceous–Paleogene extinction event resulted in their extinction. They had three-toed feet, a horny beak, a hole in the lower jaw, and an elongated pubis.

Some species like Hypsilophodon, Thescelosaurus, Othnielosaurus, Macrogryphosaurus, and Hypsilophodon also had thin cartilaginous plates. However, they did not have any armor and are not considered deadly.

(iii) Ceratopsia

Some ceratopsia dinosaurs compare with human beings

Source by: Twitter

Temporal Range: 161–66 million years
Kingdom: Animalia
Phylum: Chordata
Size: 1 m to 9 m
Mass: 23 kg to 5,400 kg

Centrosaurines were herbivorous beaked dinosaurs characterized by the unique features of their skull. They had a rostral bone on the tip of the upper jaw along with an edentulous ossification. The lower jaw’s tip was formed by the predentary bone while a parrot-like beak emerged from the rostral.

The jugal bones below the eyes made the skull appear triangular due to the rearwards extension of the skull roof’s bones that made the neck frill. Some ornamental bones were also present to differentiate species.

For example, some animals had long and hook-like bones that did not have any function.

2. Thyreophora

A brown ankylosaurus is walking on the ground

Source by: Pinterest

Temporal Range: 199.6–66 million years
Kingdom: Animalia
Phylum: Chordata
Size: 1 m to 9 m
Mass: 1,800 kg

Thyreophorans were herbivorous armed dinosaurs equipped with body armor lined up in longitudinal rows. Some early species had low osteoderms while the derived forms are characterized by prominent structures like plates and spikes. Due to their small brains,

Thyreophorans were not so sharp-minded and could easily be deceived. Moreover, they had shorter forelimbs than hindlimbs and short & broad feet that helped them run fast. Thyreophora is divided into two suborders: Ankylosauria and Stegosauria.

(i) Ankylosauria

A giant ankylosaurus on the ground

Source by: ZME Science

Temporal Range: 68–66 million years
Kingdom: Animalia
Phylum: Chordata
Height: 1 m
Length: 6 m to 8 m
Mass: 4,800 kg to 8,000 kg

Ankylosaurians were herbivorous dinosaurs having turtle-like armor in the form of bony osteoderms. Equipped with short but powerful limbs, ankylosaurids had large spines and scutes or plates arranged in a rectangular pattern in transverse rows.

The first two rows of plates were linked to each other in such a way that they formed a half-ring around the neck. Their body remained just one foot off the surface. Besides, their flexible tongue was surrounded by small loosely packed triangular teeth.

A side secondary plate allowed them to breathe while chewing different plants like cycads, ferns, and angiosperms. Due to having shorter limbs, they moved slowly at a top speed of 10 km/h.

(ii) Stegosauria

The information about stegosaurus

Source by: Encyclopedia Biannica

Temporal Range: 169–125 million years
Kingdom: Animalia
Phylum: Chordata
Height: 2 m to 3
Length: 6.5 m to 9 m
Mass: 3,100 kg

Stegosaurians were armored, low-slung, and herbivorous dinosaurs protected by armored scutes. Their body had developed spikes that were used for defense purposes.

Some species would use their high tail pointing horizontally to ward off even large predators. With longer necks and narrow heads, stegosaurus was able to approach the best parts of cycads with their beaks. Nevertheless, the decline of these plants also resulted in the extinction of stegosaurus during the Cretaceous period.

Although small teeth were present in the upper and lower jaws, these were not designed to eat flesh. Due to non-flexible jaws and a narrow toothless beak, stegosaurus liked eating plants only. The outer side of the lower jaw teeth was covered with a vertical bone plate while a flesh cheek is indicated by the structure of the upper jaw.

FAQs About the Classification of Dinosaurs

Some dinosaurs beside a lake

Source by: KRQE

What Are the 2 Classes of Dinosaurs?

Dinosaurs fall into two categories: Saurischia and Ornithischia.

What Are the Three Main Types of Dinosaurs?

Generally, most people separate dinosaurs into three groups: carnivores, herbivores, and omnivores.

How Many Kinds of Dinosaurs Are There?

There are a lot of different types of dinosaurs! To date, over 700 species have been identified and named. But there are more dinosaur types that paleontologists believe have yet to be discovered.

Conclusion

An aerolite in the sky and some dinosaurs on the ground

Source by: Forbes

Dinosaurs’ history gives us valuable information about their diet, body size, living styles, and powers. Paleontologists extract facts about the skeletal features of these prehistoric creatures from their fossils.

The primary factor considered during the classification of dinosaurs is the configuration of the pelvis. Secondary factors include their eating habits, skeletal structure, the arrangement of bones, teeth, and armor, and their defense & offensive capabilities.

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