Thyreophora, Armoured dinosaurs

Thyreophora were all known as “armoured dinosaurs” that lived from the early Jurassic Period until the end of the Cretaceous Period. Thyreophorans were mostly herbivorous but as the name suggests, their most obvious feature was their armour.

Some of the best known dinosaurs such as Stegosaurus and Ankylosaurus were Thyreophorans and the majority of these dinosaurs can be split into two groups, Ankylosauria and Stegosauria, which we will talk about shortly.

The very earliest Thyreophoran was a small dinosaur called Scutellosaurus (pictured right) which lived in North America during the Early Jurassic Period. It was only 1.2m (3.9 feet) long and had armoured plates set into its skin on its back and moved on all four limbs.

The next armoured dinosaur we know about was Scelidosaurus which was the closest relative to Ankylosauria and Stegosauria. Like Scutellosaurus, Scelidosaurus lived during the Early Jurassic Period 191 million years ago, but lived in Europe with its fossils being discovered in England and Ireland.


Pavel.Riha.CB, CC BY-SA 3.0, via Wikimedia Commons

The first discovery was named in 1861 by an English Palaeontologist Richard Owen who worked at (what is now known as) the Natural History Museum in London. He named it Scelidosaurus harrisonii after the quarry owner Harrison who discovered the fossils.


Jack Mayer Wood, CC BY-SA 4.0, via Wikimedia Commons

Scelidosaurus grew to about 4 meters (13 feet) in length and was another dinosaur that was quadrupedal (moved using all four limbs). Its armour consisted of small bony plates within its skin and was in similar style to crocodiles and lizards.

As you’ve discovered in this article the size and thickness of this armour evolved into some very impressive features which were needed to protect these herbivorous dinosaurs from predator theropods.

The remaining Thyreophoran’s, as mentioned above, were split into Ankylosauria and Stegosauria. We will cover them in below. 


Stegosaurian fossils have been found Africa, Asia, Europe, and America, and they lived during the Jurassic and Cretaceous Periods. So under the Stegosauria group heading the original dinosaurs were small, fast runners, that were protected by armoured scales.

As this group of dinosaurs evolved they developed spikes as for their own defence, and later under a subgroup called Stegosauridae, they became, bigger, heavier, slower, and moved on four limbs rather than two.

We will cover Stegosauridae below shortly.


Петр Меньшиков, CC BY-SA 4.0, via Wikimedia Commons

Stegosauria was named by Professor Nathaniel Marsh in 1877 and the vast majority of the stegosaurian dinosaurs that have been discovered so far belong to Stegosauridae. The Chinese fossils that were discovered in the in the second half of the twentieth century make up about half of all known stegosaurians, an example is the Gigantspinosaurus.


The “giant-spined lizard” was first discovered in China in 1985 and was originally thought to be another dinosaur and was only named in 1992, and the name was given in reference to its enormous shoulder spines which were believed to be for defence.

It was a medium sized stegosaur and was thought to be around 4.2 meters (14 feet) in length and weighed 700kg (1500Ibs).


Conty, CC BY 3.0, via Wikimedia Commons

These species of dinosaurs were all closely related to the dinosaur Stegosaurus (which may come as no surprise given the similarities in names), they were about from Middle Jurassic to Early Cretaceous and fossils have been discovered in North America, Africa, Europe, and Asia. The Chinese fossils that were discovered in the in the second half of the twentieth century make up about half of all known stegosaurians.

As mentioned above Stegosaurids had evolved to become dinosaurs that moved on all four limbs, their armour was well established to having erect, large, thin plates on top of their bodies.

They also had spikes on the end of their tails which would have been a powerful defensive weapon against predators as they would have used it like in a clubbing motion.

Over the millions of years it took these dinosaurs to evolve, the art of survival was going from two legged, small, quick, and lightly armoured to the opposite.


NobuTamura palaeocritti, CC BY-SA 3.0, via Wikimedia Commons

Stegosaurids were herbivores and studies have shown that they had a reduced bite force than other dinosaurs their size and scientists concluded that they were able to break off smaller branches and leaves with their teeth but anything over the diameter of 1.2cm they would have struggled. Some dinosaurs such as the Kentrosaurus may have been able to go up onto its hind legs, tail supporting, into a tripod style position where they could reach higher up plantation. Some Stegosaurids also had longer necks than some sauropods meaning they could reach higher up.

Some of the dinosaurs classed as Stegosaurids were Stegosaurus, Dacentrurus, , and Kentrosaurus (pictured above).


DataBase Center for Life Science (DBCLS), CC BY 4.0, via Wikimedia Commons


This is probably the most famous Thyreophoran dinosaur which lived in the Late Jurassic Period 150 to 145 million years ago and was discovered in 1876 and named by Othniel March the following year.

Stegosaurus grew to roughly the length of two cars and weighed one and a half tons. It had a spiked tail made up of 4 spikes that were between 60 – 90cm (2 – 3 feet) long and would have done a lot of damage to its predators if it caught them at full velocity.

Stegosaurus’s plates on its back were similar to roof tiles and therefore its name meant “roofed lizard” and was by far its most distinguishable feature. Some scientists believe they were coloured and as we can see, if they were it would have made this dinosaur even more impressive.

It ate ferns, horsetails, and cycads and may have even fed on conifer tree saplings. You can read more about Stegosaurus by clicking here.


Another Stegosauridae dinosaur family which is no where near as well known is the Loricatosaurus. This is an interesting story not because this genus has any major distinguishing features which have not been mentioned already but because of a discovery.

Fossils of this a dinosaur were first discovered in 1901 in Peterborough, England. It was later assigned to Stegosaurus priscus in 1911 and it took another 97 years before this was questioned by a British scientist and her colleagues and later the genus was changed to Loricatosaurus.

It just shows that new discoveries and even new information on old discoveries is being made all the time as our knowledge and scientific equipment grows. We will try and keep you updated with interesting stories and news with our newsletter. Sign up here.


Ankylosauria are a group of four legged, armoured dinosaurs which had a large number of spikes and armoured plates on their body. Ankylosauria Dinosaurs were first named in 1923 by Henry Fairfield.

All armoured dinosaurs or Ankylosaurids where herbivores meaning that they only ate plants. Ankylosaurids are believed to have existed in the early Jurassic Period, and may have also lived right through to the Cretaceous Period.

During this time armoured dinosaurs would have lived in what is now America. Fossil discoveries have also been found in the southern hemisphere too including Australia and Antarctica.

Armoured dinosaur Ankylosaurus

Emily Willoughby (,, CC BY-SA 3.0, via Wikimedia Commons

There are two main groups of dinosaurs that make up the armoured dinosaur family, these are Nodosauridae and Ankylosauridae, with the most recognisable armoured dinosaur being Ankylosaurus. There are other types of species of armoured dinosaur that fit into this category via sub families, which includes stegosaurus (which was a Thyreophora).

Nodosauridae armoured dinosaurs

Let’s start with an armoured dinosaur group called Nodosauridae. This particular group of armoured dinosaurs did not have the large ‘tail clubs’ as found on Ankylosauridae, instead they had distinctive large spikes. These large spikes (in some species) would have run parallel down the side of the dinosaur, others would have had large spines, with armoured plates of various sizes found across most of its body. We’ll discuss the armour found on the different types of Ankylosauria in greater detail shortly. 

Another small yet significant detail of the Nodosauridae is their beaks were smaller and narrower in comparison to Ankylosauridae beaks. With their narrower beaks, this allowed their diet to be more specific, and allowed the Nodosauridae to eat lower to the ground plants.

Palaeontologists have found fossilised remains of Nodosauridae armoured dinosaurs in North America, which Nodosauridae would have inhabited from the Late Jurassic to the Late Cretaceous period.

How big wERE the Nodosauridae?

The largest recorded Nodosauridae, Sauropelta is estimated to have been approximately 5.2m or 17.1ft in length and weighed around 2 tonnes.

Armoured Dinosaur Edmontonia

Image Source, CC BY-SA 4.0, Image source

Armoured Dinosaur Sauropelta

Dinoguy2, CC BY-SA 3.0, via Wikimedia Commons


Nodosauridae were heavily armoured dinosaurs, but Ankylosauridae or Ankylosaurids were in a completely different league. Ankylosauridae also looked slightly different with domed snouts at the front of their face.

Their head was heavily armoured and was protected by large bony plates which was a major difference between Nodosauridae and Ankylosauridae.

Ankylosaurids would have lived in the late Cretaceous period and at this time their appearance changed slightly, evolving to have much wider bodies, more armour and some species have even been found with protective bony eyelids.

How big wERE the ankylosaurids?

The largest recorded ankylosaurid was the distinctive Ankylosaurus which is estimated to have reached sizes of between 6 – 8 meters (20 and 26 ft) in length and weight as much as 8 tonnes.

Armoured Dinosaur Pinacosaurus

Slate Weasel, CC0, via Wikimedia Commons

Armoured Dinosaur Euoplocephalus

Matthew Martyniuk, CC BY 3.0, via Wikimedia Commons

Armoured Dinosaurs

Whilst other species of herbivore dinosaurs had some way of defending themselves from predators, such as stegosaurus with its tail spikes or triceratops with its huge horns on its head, this particular species of armoured dinosaurs were heavily armoured almost across their entire body.

Furthermore, Ankylosaurid’s also had a large club at the end of its tail, (more on this later) which would have been able to deliver a powerful blow when used in defence.

Let’s start by discussing an Ankylosauria’s armour.

As already mentioned, the family of Dinosaurs that make up the Ankylosauria family would have been heavily armoured over most of their body.

These armoured plates would have been rectangular in shape, with some species of having oval shaped armoured plates.

These bony armoured plates would have tightly packed together, and any gaps that may have appeared between much larger plates being filled with much smaller plates, making an Ankylosauria armour almost impenetrable.

Armoured Dinosaur armour Ankylosaurus armor

Image source, CC BY 2.0, via Wikimedia Commons

This wasn’t the case for every type of armoured dinosaur, for example Stegosaurus did not have the same level of armour on its body when compared to Ankylosaurus.

In most cases, particularly in the case of Ankylosaurus the armor around the head was particularly dense, and almost covered the entire head area, moving right down towards the neck area.

Using their tails as a weapon

The huge amount of armour wasn’t the only thing that made this particular species of armoured dinosaurs so unique, the second unique feature was that they also had a very large defensive weapon at the end of their tail which was a tail club.

Most Ankylosaurids had these very distinctive tails, with the club itself being constructed from solid bone infused by soft tissue, this allowed armoured dinosaurs such as Ankylosaurus not only to hit incredibly hard but could also absorb thousands of pounds of force once contract was made.

Scientists also believe that these tail clubs may have also been used in the mating season to attract a mate or to ascertain dominance over a rival.

Armoured dinosaur club tail Ankylosaurus tail

Modified from Arbour et al. (in press)., CC BY 2.5, via Wikimedia Commons

Nodosauridae Armour

Not all Ankylosauria’s had clubs at the end of their tails, some such as nodosaurids had very flexible tail tips and would have still been heavily armoured with large bony spikes and plates particularly towards the head area.

Armoured dinosaurs such as Sauropelta had huge spikes or spines on their shoulders and neck area. Sauropelta armoured spines were the largest on the shoulder, and decreased in size down the body until the hip area.

Once at the hip area, Sauropelta’s armour then changed shape slightly into triangles which ran all the way down to the tail area. Once at the tail area there was no tail club or spikes.

How big were the armoured dinosaurs?

Nobu Tamura email:nobu.tamura@yahoo.com, CC BY-SA 4.0, via Wikimedia Commons

To be able to carry such large spins on their shoulders Nodosaurids would have had very strong shoulder muscles. Their wide shoulder muscles would have been able to withstand a huge amount of force, more than enough to defend against a theropod. 

Scientists also theorise that these large spikes could have also been used in the mating season, with females being attracted to males with much larger spines on display.


Below is a list of Ankylosauria Dinosaurs that make up the most of the major group. This list will be updated as soon as a new specimen is discovered. In the meantime, you can start discovering more information about the individual types of Theropods by clicking the links below: 


Last Updated on 15/07/2022 by