(What was there before, a chicken or an egg? Today we will ask ourselves the same kind of question: Were all carnivorous dinosaurs theropods, and were all theropods carnivorous? And, after all, what did the meat-eaters of the dinosaur world have to do with theropods? Let's get to the bottom of this...)
Due to disputes over different approaches to classification, the terms "carnivorous" and "theropod" are sometimes used as synonyms, up to the complete fusion of their meanings. As a consequence, this often confuses curious lovers of paleontology. Therefore, let us clarify these things, first of all, differentiate these concepts.
There weren't single carnivorous dinosaurs that were not theropods even though not all theropods were carnivores, although most of them seemed to be.
Let's start with the basics, so what exactly is a theropod?
Theropods are one of the two major subgroups of the group of saurischian dinosaurs (dinosaurs with a reptile pelvis). For a long time, they were considered to be predominantly carnivorous, although this theory is increasingly being questioned by one part of the scientific community and evidence has even been found that some of them were herbivorous.
Theropods - are biped dinosaurs and are mostly predators, although there are exceptions. For example, representatives of the theropods, such as Therisinosaurs, could just as successfully eat as scavengers, as some plants, and ornithomimids ate only plants. But, despite their food preferences, all of them moved only on two legs, had the highest speed and maneuverability among other lizards, and were at the top of dinosaurs.
The first varieties of theropods relatives began to appear in the early Triassic, at a time when there was a single unified supercontinent Pangaea.
Archosaurs (pre-dinosaurs) of the early Triassic then resembled the body structure of today's crocodiles. After the global upheaval that occurred at the boundary of the Permian and Triassic, there was not so much alive, and therefore some archosaurs had to try hard to get enough to feed themselves. But the giant insects at the time also evolved. They became faster and faster, their vision became sharper, their reaction developed, and therefore, to hunt such progressive animals it was also necessary to change. Even though the ancient ancestors of dinosaurs were still moving on four widely spaced limbs, more and more often they, in pursuit of take-off from the grass prey at an accelerated pull the front extremities from the ground, and the rear made a strong leap. Later, they began to take several steps on all the stronger hind limbs until their massive body fell again on the front legs. Then they could run an already impressive distance on their hind limbs before falling on their front legs to rest. And finally, after a few million more years of evolution, their hind limbs developed to such an extent that it made no sense for them to fall back on four paws.
At the same time, against the background of these ever-increasing jerks on two limbs, archosaurs also developed bipedality, i.e. the structure of the musculoskeletal system was rebuilt in such a way that their legs were more and more leveled, at the same time moving under the body, and finally, somewhere around 230 million years ago, the first varieties of theropods appeared, perfectly moving on two hind legs.
Since almost all of them had a massive and heavy skull, while walking and running on the two hind limbs, they needed an impressive counterweight, which became an overdeveloped powerful tail, which besides, often used them as a battering ram while hunting.
In contrast to the hind limbs, the anterior limbs began to degrade. Scientists have not yet come to a common opinion, for which theropods used their small three-finger limbs. Some agree that with the help of their creatures were laid on the ground, others assume that they were used only during mating.
But the speed of movement is not the only advantage that theropods have found with the ability to walk on their hind legs. Their ancient ancestors, the Archosaurs, had to crawl among the dense vegetation, not being able to look over it to be prepared for the attack by more dangerous predators or to see more space for edible insects. Now they could rise above the edge of the vegetation due to their huge height. Some species of theropods, such as the Spinosaurus, were up to 15 meters long. And small representatives of theropods were able to jump out of the grass due to their powerful limbs and lightweight, thus also having a good view of the surrounding area. In the process of evolution, they were the beginning of such a large variety of vertebrate animals as birds.
Let's highlight the main distinctive features of the theropods we've been able to identify:
Technically, no, all carnivorous dinosaurs are considered theropods, but here we can make a mistake if we consider archosaurs or other species of prehistoric carnivorous animals living in the time of the dinosaurs.
For example, if you turn to the detachment of pterosaurs, or as they are otherwise called "flying lizards", you can find some quite interesting facts.
1. Representatives of this group lived simultaneously with representatives of the theropods (from the late Triassic to the end of the Cretaceous period), although in fact in different interpretations they are considered pre-dinosaurs, or completely separate from the dinosaurs species.
Pterosaurs are often referred to as "flying dinosaurs" in the popular media and the general public, but this is scientifically wrong. The term "dinosaur" is limited to those reptiles that originated from the last common ancestor of the Saurischia and Ornithischia groups, and the current scientific consensus is that this group excludes pterosaurs as well as various groups of extinct marine reptiles such as ichthyosaurs, plesiosaurs, and mosasaurs.
2. Unlike theropods, the representatives of pterosaurs could not move on two legs. However, unlike theropods, they were able to fly as well as move on four limbs.
3. Traditionally, all pterosaurs were seen as fishermen snatching their prey from the water surface. In reality, however, most pterosaurs are now regarded as terrestrial predators or insect eaters.
( Interesting fact: There are known cases when pterosaurs were eaten by theropods. In one of his works, the French paleontologist Eric Buffeto researches an early Cretaceous fossil consisting of three cervical vertebrae of a pterosaur with a broken Spinosaurus tooth, most likely an irritator stuck in one of them. The vertebrae are not known to pass through the predator's digestive system because they preserved the joints )
Yes, in fact, crocodiles are indeed prehistoric carnivorous animals not belonging to the theropod group and they lived in the time of the dinosaurs, but like the pterosaurs, they are not dinosaurs, not scientifically speaking. They are actually cousins from the same ancestors, which can sometimes be confusing.
If we do not take into account the fact that officially pterosaurs and crocodiles are not considered to be dinosaurs, their representatives may well be considered by the general public to be carnivorous "dinosaurs", not belonging to the group of theropods, as they lived at the same time with theropods, and in most cases, these creatures fed on meat. But this is not scientifically accurate.
If you are a dinosaur enthusiast and you love carnivores and theropods we advise you to take a look at our plush collection. You will find some of the most dangerous and ferocious carnivores such as the famous tyrannosaurus rex or the dreaded spinosaurus.
Discover them by clicking on the picture!