Theropoda is one of the two major suborders within the Saurischian order. Usually referred to as theropod dinosaurs, the name stems from thēríon and podós from the Ancient Greek language, meaning “wild beast” and “foot”, respectively. It’s an ironic name, as these prehistoric beasts had feet more akin to modern birds than beasts.
In this guide, we’ll show you all there is to know about the Theropoda suborder, which contains all of the carnivore dinosaurs. You’ll also see the differences from the sister Saurischian group, Sauropoda. Finally, expect to see some top theropod examples.
What is the Theropoda Suborder?
The name Theropoda was first instilled in 1881 when O.C Marsh named it. It was meant to house the Allosaurus family, but in the end, the taxon expanded to include all carnivore dinosaurs. Within this suborder is the group from which modern birds evolved.
The Therapod taxonomy actually has an interesting history of classification from that point on. E.D. Cope had placed all carnivore dinosaurs in a group called Goniopoda in 1866, which meaned “angled feet.” With Marsh’s new title, the word Theropoda would only last until the early 20th century.
Friedrich von Huene was dissatisfied that all meat-eating dinosaurs were placed together. He retained the Saurischia order but broke it up into Pachypodosauria and Coelurosauria. The latter only had a small number of theropods, while the former had larger theropods and sauropods. When W. D. Matthew and Barnum Brown tried to bring back the term Goniopoda in 1922, other scientists refuted it.
It was in 1956 when Alfred Romer decided to reclassify the Saurischia order into two main subgroups: Theropoda and Sauropoda. The main infraorders were divided between Deinonychosauria, Coelurosauria, Carnosauria, Oviraptorosauria, Ornithomimosauria, and Deinocheirosauria.
When the clades further developed between 1990 and the 2000s, we finally saw the Theropods split between Coelophysoidea, Ceratosauria, and Tetanurae, which are still the three main groups today. It was in 1986 when bird-like theropods were placed in a group called Maniraptora within Tetanurae.
Which characteristics define Theropods?
Now that you have a general introduction to the Theropoda suborder, it’s time to break into song and dance about the chief characteristics that set it apart from the Sauropoda group within Saurischia. Some of them you’ll simply know from looking at them, while other details are more intricate and interesting.
Teeth and Diet
While all of the carnivores are slotted within this group, not all Theropods are carnivores. Some other diets include herbivores and insectivores. There are also sub-groups related to modern birds that had similar avian diets.
The common characteristic relates to the teeth, irrespective of the diet. They all had serrated, sharp teeth to tear through flesh and food, helping them survive. All of the carnivores reflected some form of predatory behavior, even those with fossilized lizards discovered in their bellies.
However, it’s the tooth’s shape, among other factors, that sets theropod families apart. Where once paleontologists placed only carnivores in this group, Therizinosaurus was the first dinosaur to break the rule. With sharp claws and beaks, fossils revealed that they were mostly herbivores. Other diets soon emerged, such as the omnivorous troodontids or the fish-hunting Spinosaurus. Some genera used rocks to help with digestion, such as Baryonyx.
The almighty Tyrannosaurus Rex falls within the Theropod scope, and for a long time, it was believed to be the largest carnivore of its time. However, more fossils were found, and there’s still a debate about whether T. Rex or Spinosaurus was larger. Equal to size or larger were Giganotosaurus and Carcharodontosaurus.
Since modern birds descended from theropods, many state that the ostrich is the current largest living theropod. As time rolled on during the Jurassic and Cretaceous periods, dinosaurs shrank in size. While some skulls grew larger, their arms became shorter since they weren’t as necessary as in the past.
There were also relatively tiny theropods in prehistoric times. On the non-avian side was the Anchiornis huxleyi, which was a troodontid. It was only about 1 foot long. The modern bee hummingbird is the current smallest theropod, being only 2.2 inches in length. As you can see, they evolved into smaller creatures over time as they adapted.
Feathers, Skin, and Scales
An integument is an outer layer that protects an organism or part of a plant. When it comes to dinosaurs, we usually refer to the skin, feathers, or scales when discussing integuments in the theropod classification. In this regard, we have diverse coverings and layers among the many sub-groups and families.
The following integuments have been noted on various dinosaur classifications:
- Feather-like filaments: especially on coelurosaurs or small theropods outside Coelurosauria;
- Small bumpy scales: on most huge theropods, especially massive carnivores;
- Osteoderms (massive scales with bony cores): mostly with ceratosaurs, such as Carnotaurus;
- Large quills: discovered on massive avian theropods, like Therizinosaurus;
- Completely feathered: had small scales on the feet, such as dromaeosaurids;
- Scales and feathers: some theropods had an even mixture of scales and feathers, such as Scansoriopteryx and Juravenator.
Scientists use two methods to determine the growth rate in dinosaurs, which we’ll cover in a separate article. In summary, this is when their applications work best:
- Extant scaling (ES): You don’t need a complete skeleton, and you can use it across a wide range of applications;
- Volumetric density (VD): Requires as much of the entire skeleton as possible to determine what the possible mass was, but you can establish specific details, such as movement and center of gravity.
The moral of the story is that there isn’t a clear growth rate across the entire Theropoda group. When it comes to non-avian theropods, it seems to depend on the size and mass of the species. The mass is relative to the growth rate, meaning it grew faster if it was larger. In comparison, T. Rex had the same development as an elephant, starting fast until maturity and then slowing down from then onwards.
Gait and Stance
If you’ve seen an ostrich or modern bird walk on the ground, you’ll have a general idea of the theropod’s stance. It was mostly bipedal, which set it apart from the quadrupedal Sauropods. You may also have noticed that most of them had short forearms depending on the family.
There have been many theories about how theropods stood, walked, and ran in prehistoric times. With giants like Tyrannosaurus and Giganotosaurus, many scientists believed that the tail formed a triangular shape with the legs, providing balance and support while hunting. However, with the modern comparison with birds, not everyone agrees with that statement anymore.
Senses and the Nervous System
The most important aspect of the nervous system and sense among theropods are from the ancestors of birds, especially Coelurosauria and maniraptorans within the group. Based on brain casings that have been preserved, the cerebrum seemed to increase when measured in proportion to the test of the brain, enhancing the senses.
Movement of the Forelimb
Sadly, theropods had limited movement in their forearms, especially by the elbow and wrists. Humans have greater flexibility, and we can turn our hands so the palms can face backward or downward. Theropoda and a few other Saurischian dinosaurs didn’t have this luxury and could do little with their forearms. Some even had their wrists and elbows locked in place, with greater reliance on the muscular hind legs, tail, and jaws.
However, this wasn’t true of all theropods, especially the coelurosaurs within the avian families. As with modern birds, they had improved flexibility at the shoulders and could move their wrists with better mobility. Yet, the hands remain in place, and their fingers could hardly move apart from one another.
Some fossil remains and claw marks have shown that some Theropoda dinosaurs were excellent swimmers. Considering the fact that Baryonyx and Spinosaurus loved eating fish in their diets, this shouldn’t come as a surprise.
Some footprints were found where rivers and water used to be, revealing how they could have moved and then swam into deeper waters for some food. However, they probably made sure their feet were near the waterbed just in case something went wrong, as they weren’t as proficient as the swimming reptiles of that time.
The Sub-Groups of the Theropoda Suborder
At this stage of our Theropod guide, you should already have an idea of the three main groups in the Theropoda suborder. We’ll tackle each of these individually in separate articles, but we just want to give you a brief overview of each one.
Coelophysoidea is a superfamily within the Theropoda group. Many of them existed during the Late Triassic and made it into the Early Jurassic period. It derives its name from the main Coelophysidae family, but it was once mistakenly known as Podokesauridae.
Of the coelophysoid dinosaurs, you’ll probably recognize Dilophosaurus the most. It was made popular by the Jurassic Park books and movies, while also moving over to many games, such as ARK: Survival Evolved. Other dinos in this superfamily include Procompsognathus, Coelophysis, Zupasaurus, Dracoraptor, and more.
You may have heard the term Ceratosaur before, and now you know in which suborder it falls. Most of the carnivores that don’t share a close relationship with modern birds are here, especially those who are more connected to Ceratosaurus. Within this group are three main sub-divisions, namely, Ceratosauridae, Abelisauridae, and Noasauridae. It’s easy to see from which one it takes its name.
Most of them lived during the Early Jurassic period. Paleontologists are still baffled why they seem to have vanished during the Middle Jurassic ages. Popular ceratosaurid dinosaurs you may know are Ceratosaurus, Abelisaurus, Majungasaurus, Carnotaurus, Aucasaurus, Indosaurus, and Rajasaurus.
If you’re looking for the group that has most of the theropods, you’ve found it. With a name that means “stiff tails”, these dinosaurs are the ones that are more closely related to modern birds. You’ll also find most of the titans here, such as Tyrannosaurus, Giganotosaurus, and Spinosaurus.
The four main groups within Tetanurae are:
We’ll cover these groups in more detail within other articles.
Families within Theropoda
We have a special division on our Ancient Beasts site for dinosaur families, and we intend to cover every Theropoda group there is. Since the list is long, we don’t want to go into too much detail here.
For now, here’s a quick overview of the more popular Theropod super-families and families:
What are Some Dinosaur Examples of Theropoda?
We’ve already mentioned some of the most popular theropods you’ve seen in movies and games and hardly need a mention. Still, we love these carnivorous dinosaurs so much that we can’t leave without having a small discussion about them. Welcome to our tiny Theropoda library.
We bet you know this one. Meet what they called the king of the dinosaurs, Tyrannosaurus Rex. It received this title as it was the largest known carnivore at that time. Of course, we’ve since found fossils to rival it, but that doesn’t mean it ended Rex’s reign at the top of fans’ hearts.
Many will recognize T. Rex by several traits. The most popular characteristics are the massive skull and small arms. The latest Carcharodontosaurus discoveries reveal that perhaps these carnivorous dinosaurs had longer arms earlier in history, growing shorter over time.
Tyrannosaurus lived in the area now known as North America during the Late Cretaceous. It’s believed to have been the last Tyrannosaurid before the final mass extinction event.
A rival of the Carnotaurus in the South American landscape was Giganotosaurus, and it also lived during the Late Cretaceous. There’s still some debate on which was larger between this meat-eating dinosaur and Tyrannosaurus. In many games that depict it, it’s usually shown as larger than T. Rex, despite some evidence to the contrary.
Paleontologists believe Giganotosaurus was homothermic. This term means that it may have been slightly warm-blooded, somewhere between reptiles and mammals. It also meant that these dinos probably developed faster than most theropods and could open and shut its massive jaws relatively quickly.
Here’s a massive theropod that reigned in North African locations during the Late Cretaceous. It was almost equal in size to Spinosaurus, Giganotosaurus, and Tyrannosaurus, if not larger in some cases. It has two species, the fossils of which have been extensively analyzed over the past decades.
Much of that which is known stems from the upper and lower jaws, specifically the remarkable teeth. As a matter of fact, the “Carcharodon” is taken from the taxonomy of the Great White Shark, as their teeth are similar. Surprisingly, Giganotosaurus falls under the Carcharodontosaurinae clade, so they’re seen as distant cousins from across the ocean.
Meet Carcharodontosaurus’ direct rival during the Late Cretaceous in Northern Africa. The Spinosaurus was massive and had a huge sail on its back. The initial remains were discovered in Egypt and studied by the same paleontologist named Carcharodontosaurus, Ernst Stromer.
Matching the sizes of the aforementioned carnivores, it adapted to hunting in rivers and deep waters, enjoying the taste of fish. There’s a good chance it hunted terrestrial animals, but it seems its preferred diet was in the waters. Another interesting fact is that one of the hand’s digits was longer than the rest, with an enlarged claw. We often imagine it spearfishing with that claw.
The almighty Carnotaurus is within the Abelisauridae family and only has one known species so far. Of all the fossils found in the southern hemisphere, it’s probably the theropod that’s been studied the most with how many bones have been discovered. While it was also alive during the Late Cretaceous, as with Tyrannosaurus, it resides in the South American landscape known as Gondwana.
Two of the popular traits of the Carnotaurus were the muscular neck and horns on the skull. Since it has such tiny forearms, it probably battled other predators by ramming with its horns. The powerful legs made it one of the fastest theropods of its time. While it could hunt and kill Sauropods, there’s a good chance it aimed for smaller prey.
As the final theropod on our list, the Majungasaurus also falls within the Abelisauridae family. It lived at the end of the Cretaceous period, towards the latter part when the extinction event occurred. It mostly lived in the area we know today as Madagascar, which still formed part of the African continent.
A common trait of Majungasaurus, as with other abelisaurids, is that it had a small snout. The forelimbs were short, while the hind legs were thick and strong. The top of the skull had a strange, domed horn that made it almost look like a huge Pachycephalosaurus. Not only did it hunt sauropods, but it may have been a cannibal and eaten its own kind.
How does Theropoda fit into the 7 major dinosaur groups?
The dinosaur kingdom has seven major groups within which we place all of the known dinos. You’ll notice it doesn’t follow the accepted Taxonomy, as some of them are groups that fall within the other groups.
The seven major dinosaur groups are:
You’ll note that Theropods are highlighted as a major group on their own. That shows you just how significant it is in the world of dinosaurs. If you’re looking for action with mighty jaws and dangerous claws, you’ll find them in that group.
Final Thoughts on the Theropoda Suborder
The Theropoda suborder is exhilarating, drawing appeal from children and adults who love the vicious, meat-eating dinosaurs. Many names on this list feature in popular entertainment media and toys, with their fame spreading worldwide.
Of course, the latest interest is with the theropods that have a direct relationship with modern birds. It helps us understand how some of the dinosaurs actually survived the extinction-level event said to have wiped them all out.