April 4, 2022 Scott Kraus

Psittacosaurus was a Cretaceous Ceratopsid

Psittacosaurus (pronounced SIT-ah-co-SAWR-us) was a primitive Ceratopsid that lived 130-100 million years ago in the Early Cretaceous period. Although it is related to the better-known Triceratops, one wouldn’t know it by appearance. Psittacosaurus was a small bipedal dinosaur that was a fraction of the size of some of its larger family members that appeared later during the Cretaceous.

Quick Facts

About Psittacosaurus

With over 400 skeletons found so far, Psittacosaurus is a well-documented genus. Paleontologists have discovered fossils from every age range—from hatchling to adult. This is a rarity in the field of paleontology so Psittacosaurus research is vital for studying growth rates and reproduction. It is also the most species-rich genus in the class of dinosaurs. As many as 17 species have been classified as a Psittacosaurus, although it should be noted that not all of them are valid. The verified number of species is eleven at the moment.

What Did Psittacosaurus Look Like?

Psittacosaurus didn’t look like the typical Ceratopsid. Since it was one of the first dinosaurs in the evolution of the suborder, Psittacosaurus was rather small. The largest species only reached 6.5 feet in length and most members of the genus weighed between 40 and 80 pounds. Due to the number of species, there was a lot of variation in the physical characteristics of each dinosaur. We will cover the general attribute that were present in all species.

The most easily identifiable part of a Psittacosaurus is its large beak. The beak was formed from rostral and predentary bones and was used to sheer thick foliage and possibly to crack hard nuts and seeds. Unlike most Ceratopsids, Psittacosaurus did not have an elaborate frill. It did have a ridge near the back of its skull that could have evolved into a frill over the course of a million years. The frill wasn’t the only feature missing from the skull of Psittacosaurus though. It also didn’t have any of the prominent horns that Ceratopsids are known for. So without a frill and horns, Psittacosaurus’s face looked more like the face of a modern-day turtle.

Another unique trait of Psittacosaurus was its form of locomotion. Instead of lumbering around on four feet, Psittacosaurus ran around quickly on two legs. Bipedal movement wasn’t that rare in early Ceratopsids. Psittacosaurus couldn’t walk on four legs because its forelimbs were puny and mostly useless. They were inflexible and short while measuring only half as long as the powerful hind limbs. All of Psittacosaurus’s limbs ended in four fingers. This was an oddity because every other Ceratopsid had five.

What did Psittacosaurus eat?

Psittacosaurus was an herbivore but since its teeth weren’t suited for grinding and chewing food, paleontologists had to formulate a theory to explain how it digested food. They got their answer when they discovered a fossilized Psittacosaurus with gastroliths in its abdominal cavity. This leads researchers to believe that Psittacosaurus had to swallow stones in order to grind food in its digestive tract. It is possible that Psittacosaurus also had a gizzard in their digestive systems in order to process food in the same manner that today’s birds and reptiles do.

Another important discovery in regards to Psittacosaurus’s eating habits was the realization that its lower jaw could slide forward and backward. This range of motion in its bite would have allowed it to shear foliage. The self-sharpening teeth behind the beak would have diced up the plant material to some extent before it was sent into the digestive system to be further broken down by gastroliths and stomach acids. In addition to the ability to slide forward and backward, the lower jaw could fit inside the upper jaw, which would created a useful nut or seed cracking motion.

How did Psittacosaurus Move?

As mentioned earlier, Psittacosaurus was entirely bipedal in movement. The small front limbs of Psittacosaurus weren’t useful for much of anything, let alone supporting the dinosaur’s weight. It is believed that these bipedal herbivores were sociable dinosaurs and lived in herds. Additionally, well-ossified bones of juvenile Psittacosaurus fossils which were still in the nest support the idea that parents took care of hatchlings for an extended time and might have supported them into adulthood. These ossified bones are an important determining factor because newly hatched reptiles have soft bones. These specimens must have been in the nest for some time in order for their bones to stiffen.

Some paleontologists have posited that Psittacosaurus might have engaged in some aquatic activity. The idea more than likely took off because so many Psittacosaurus fossils were deposited in a lake bed. To support the claim, scientists point to the position of the nostrils and eyes. The location of the nostril and eyes would have given Psittacosaurus the ability to breathe and see while swimming. The short front limbs might have seen some use as paddles, but Psittacosaurus would have had a much better method to propel itself with its tail.

Where did Psittacosaurus live?

The Psittacosaurus genus has a lot of species, but every single one of them resided in Asia during the Cretaceous period. Discoveries have been made in China, Mongolia, and Russia. Another supposed species of Psittacosaurus has been located in Thailand, but for now it isn’t considered to be an official member of the genus. Although Psittacosaurus did not have an extensive range, there were plenty of individuals in Asia during its time on Earth. Psittacosaurus fossils are so ubiquitous that scientists now use them as an index fossil to help determine the age of the soil when they are found. Nearly all sedimentary formations of the late Barremian and Albian stages contain evidence of Psittacosaurus existence.

The Discovery of Psittacosaurus

The first Psittacosaurus fossil was found in Outer Mongolia in 1922. Although the discoverer’s name is unknown, we do know who gave this dinosaur its name. When the species was brought to the attention of Henry Fairfield Osborn, paleontologist and president of the American Museum of Natural History, a year later in 1923, he named it Psittacosaurus because of its parrot-like beak. The translation from its Greek name means “parrot lizard”.

Dinosaur Feathers?

Scientists now know that at least one species of Psittacosaurus had quill-like structures on its lower back and tail. This series of hollow, tubular bristles were about 6” long. Although this part of Psittacosaurus’s anatomy appears to be feathers, they are not. Protofeathers, which have been found on some animals prior to their evolution of true feathers, have been used as comparisons to reach this determination. Even if these bristles were protofeathers, they wouldn’t have been in the ideal location for flight. For this reason, scientists believe that this feature was used either for communication or mating. Without seeing these quills in action though, we may never know their purpose.

The Importance of Psittacosaurus

Psittacosaurus’s importance is a result of the multitude of fossils that the genus has provided to paleontologists. The wide age range of fossils allows scientists to research growth rates and cycles of reproduction. Results have shown consistently that Psittacosaurus grew at a rapid rate, which is true for most dinosaurs. Their lifespan reached 10 or 11 years. It is known from fossils found in the nest that Psittacosaurus was gregarious and it is believed that many other herbivores may have been gregarious out of necessity.

Psittacosaurus is also vital within the Ceratopsid suborder. When “ceratops” comes to mind most people think of large quadrupedal dinosaurs with frills and horns, but these large creatures had to evolve from something smaller. One major change that occurred as Ceratopsians evolved was the shift from walking on two legs to four. A pronounced ridge near the back of the skull of Psittacosaurus lends itself to a frill. The prevalence of Psittacosaurus fossils can be studied alongside Late Cretaceous Ceratopsids to really see the evolution of this genus in action!