What are Theropod Dinosaurs?
Dinosaurs in general always enjoy a certain level of popularity, from the long-necked, massive Sauropods to the frilled, horned Ceratopsians…but there is one group that always seems to take the number one spot in dino notoriety (dinotoriety?). That group is known as the Theropods.
Theropods are a widely varied dinosaur group that contains some of the heaviest hitters among the dino fandom, including Tyrannosaurus rex, Velociraptor, and Allosaurus. What is the common thread that makes these guys so popular? They’re all predators, and well-equipped ones at that: their sharp teeth and claws are surely responsible for a large part of their draw. It also makes them prime candidates for films and TV shows glorifying dinosaurs as terrifying monsters, which introduces them to a wider audience and increases their popularity.
But Theropod dinosaurs weren’t all giant toothy predators. While some, like the nearly 50 foot long Giganotosaurus, were indeed huge and toothy, many were quite small. Even Velociraptor, though movies often depict it as bigger than a human, wasn’t much bigger than a modern day turkey in reality. They weren’t all meat eaters either. Some Theropods were herbivores, eating only plants. Others ate fish, or eggs, or insects. And while teeth are a big part of their appeal, some Theropods were entirely toothless! So what is it that actually makes a dinosaur a Theropod?
The main features found in Theropod dinosaurs are: hollow bones, and three main fingers on each forelimb and three main toes on each foot. They may have more or less fingers and toes on each foot, depending on the species, but when there are more they are usually smaller than the others, and when there are less it’s usually because there were once three, but evolution caused one of the digits to shrink out of existence over time.
Look at T. rex, for example: while each hand has two fingers, its earlier relative Yutyrannus had three fingers on each hand, meaning somewhere along the way as the arms of Tyrannosaurs got smaller, their third little finger disappeared. Looking at T-Rex’s feet, you’ll also see it has four toes on each, but only three even touch the ground, the fourth claw is much smaller.
|Yutyrannus||Tyrannosaurus Rex (with feathers)|
Theropods developed in the Late Triassic Period, around 230 million years ago, and became extinct around…just kidding, they never became extinct! While most dinosaurs, including many Theropods, died off at the end of the Cretaceous Period around 66 million years ago, a small group of Theropods just kept on trucking, and today you know them as “birds”. Yes, if you’ve been following our blog, we’ve mentioned many times that each and every bird is actually a living, breathing dinosaur!
But even before there were birds, there were still feathers, and Theropods developed these features long before they could fly. So what did feathers do in these earlier dinos? One possible explanation is that they regulated the animal’s temperature. They also may have been brightly colored to use for display. One early Theropod, Coelophysis, was a long-necked, slender dinosaur that grew to about ten feet long. Though it wasn’t a bird, it was an early Coelurosaur, the group of dinosaurs that would evolve into birds. Because of this, scientists believe it might have been covered in a coat of fine feather-like fibers.
Birds first developed in the Late Jurassic, around 165 million years ago. Archaeopteryx is one of the most famous bird-like dinosaurs, and is referred to by some scientists as “the first bird”. Since we now know that birds are, in fact, dinosaurs, it is difficult to tell exactly when a dinosaur becomes a bird. But many dinosaurs like Archaeopteryx were completely covered in feathers that closely resemble those of modern day birds. Some, like Archaeopteryx, could even fly like today’s birds. Though Archaeopteryx was quite small, many Theropods would continue to develop and grow quite larger, with the Early Jurassic double-crested Dilophosaurus and the Late Jurassic nose-horned Ceratosaurus both growing around 20 feet long. These dinosaurs were less likely to have been covered in feathers, as the larger an animal gets, the less it relies on such features to control its body temperature. This can also be reflected in large mammals like rhinos, hippos and elephants, which are nearly hairless, compared with smaller mammals that are covered in fur.
It isn’t known exactly how many Theropods had feathers, as they are not often preserved in the fossil record. Occasionally, feather imprints are found around a skeleton, or structures called quill knobs are found in the bones which indicate the presence of feathers. Using these discoveries and applying it to related dinosaurs, we can begin to get an idea of which ones may have had feathers. Many of the most bird-like dinosaurs are closely related to the Dromaeosaur family, which contains the popular Velociraptor (now believed to have feathers), and the Microraptor (which had four wings total, on both its arms and legs).
As we mentioned, some Theropods were completely toothless, and we’re not just talking about birds. Anzu was a member of a group called the Oviraptorosaurs, which at most had four teeth in total, though more advanced examples (like Anzu) had no teeth whatsoever. Deinocheirus, an Ornithomimisaur, had a duck-like, toothless bill. Both Anzu and Deinocheirus were likely feathered, and Deinocheirus even had a structure called a pygostyle in its tailbones that, in modern birds, indicates fan-like tail feathers.
Theropods remain a popular group, and it’s likely that movies, toys, video games and popular culture will continue to show off their teeth and claws, even if they often don’t get the feathered part right. Hopefully, we’ve shown you that this unique group of dinosaurs was remarkable beyond just those few pointy features…after all, they’re the only dinosaurs still around today! So the next time you spy a chicken on the farm or a cardinal out the window, remember…its ancestor was basically a T. rex!
Click on the images above to buy any of the toys shown, or check out these other awesome Theropod dinosaur toys!
Guanlong - an early relative of Tyrannosaurus rex
Suchomimus - a Spinosaurid with a crocodile-like mouth
Masiakisaurus - a small Theropod with a unique lower jaw
Acrocanthosaurus - a large Cretaceous predator with a low sail on its back