Name: Psittacosaurus, assigned species: P. mongoliensis, P. sinensis, P. xinjiangensis, P. meileyingensis, P. sattayaraki, P. neimongoliensis, P. ordosensis, P. mazongshanensis, P. sibricus, P. lujiatunensis, P. gobiensis
Name Meaning: Parrot Lizard
First Described: 1923
Described By: Osborn
Classification: Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Marginocephalia, Ceratopsia, Psittacosauridae
Requested By klipty!
Psittacosaurus is one of the best known non avian dinosaurs. It was a small little herbivore, about 2 meters long, and its been found in China, Mongolia, Russia, and also potentially Thailand. It lived for a long time, from the Barremian to the Albain ages of the Early Cretaceous, about 123.2 to 100 million years ago. It is the most species rich non avian dinosaur genus, with nine to eleven species being recognized to date. All of the species in this genus were about the size of gazelles, were bipedal, and had a very powerful beak on the upper jaw. One species, P. mongoliensis, has also been found with long quills on its tail and lower back, and it’s reasonable to suppose that the other species did as well (re: Kulindadromeus). Psittacosaurs represent a stepping stone on the long line of evolution to neoceratopsians, sharing many similar traits to Triceratops and Protoceratops. Over 400 fossils have been found for this genus, with many different age classes allowing for a very detailed picture of its life history to be known.
Psittacosaurus was well adapted for eating plants, with teeth that could easily slice through them and they were self-sharpening. They couldn’t grind (chew) food, though, so they potentially swallowed gastroliths to grind up food in the stomach; indeed, some Psittacosaurus specimens have been found with rounded stones in their stomachs. Its lower jaw was good at sliding, allowing for shearing tough plants. It probably was a selective browser, having a specific preference for certain plant parts but not necessarily being limited to just eating them. They also probably ate a lot of seeds. Their upper and lower jaws behaved as a single unit, and they could only slide their jaws forward and backward for a shearing action.
Specimen with Integuments on the Tail. Source: http://en.wikipedia.org/wiki/Psittacosaurus#mediaviewer/File:Psittacosaurus_mongoliensis.jpg
The animal has been shown through its scleral rings to have been cathemeral, or active throughout the day and night at short intervals. It is known from a wide variety of aged specimens, with a hatchling skull that is only 4.6 centimeters long. These animals grew rapidly compared to reptiles and marsupial mammals, but slower than modern birds and placental mammals, indicating that they had a mesothermic metabolism (or somewhere between cold and warm blooded, closer to warm, but not quite as fast as that of birds and placentals.) It lived between 10 and 11 years. These were extremely social animals, with many sites having lots of specimens found and nests, with juveniles and adults living together. Young psittacosaurs could chew their own food, meaning the shearing action of adults was developed later. They also have been shown to care for their young, with older individuals caring for the hatchlings.
It has been proposed that Psittacosaurus was semi aquatic, using its tail like that of a crocodile’s to propel through the water. They also have been found in association with lake deposits, have eyes and nostrils positioned for semi aquatic life, tails that could easily propel through the water, and gastroliths could be used as a ballast. More evidence will, of course, need to be found. It was a prey animal for the region and juvenile specimens have been found in association with predatory mammals, one of the rare examples of mammals eating on dinosaurs. It probably was subject to R-selection, or where many offspring are produced to counteract loss to predation. It was so common it was probably a staple animal in Asia at the time, sort of like a Cretaceous sheep. It probably was also fed on by dromaeosaurids and crocodiles.
The species are distinct from one another mainly due to head shape, given that many specimens of Psittacosaurus are only known from the skull. P. mongoliensis is the type species, and it lived alongisde Protoceratops, Oviraptor, and Velociraptor. It had a flat skull, and a flange on the lower jaw, which is not particularly prominent. Protiguanodon mongoliense, Psittacosaurus protiguanodensis, P. osborni, P. tingi, and P. guyangensis are all junior synonyms of this species.
P. sinensis is also from Asia, specifically China (as opposed to Mongolia.) It has fewer teeth than other species and a smaller skull, with horns flaring out from the jugals (cheeks) that are wider than any other Psittacosaurus species except for P. sibiricus and P. lujiatunensis. The skull is thus wider than it is long and it also had smaller horns above the eye, and a slight underbite. P. youngi is a junior synonym of this species.
P. sinensis Source: http://images.fineartamerica.com/images-medium-large-5/three-juveniles-psittacosaurus-sinensis-roman-garcia-mora.jpg
P. xinjiangensis was found in Xinjiang China, and it also had a prominent jugal horn that is flattened out on the front end. It also had very long pelvic bones and femurs compared to other species. P. meileyingensis is also from China, in Liaoning, and had the shortest snout and neck frill of all the species. Thus it had a nearly circular skull. It had a triangular eye socket and prominent flanges. P. sattayaraki was found in Thailand in the Khot Kruat Formation, and its validity has been question, however it had flanges similar to P. mongoliensis, but less pronounced. It would be the southernmost species of the genus if the material is considered to be valid.
P. neimongoliensis is from Mongolia, and it had a distinctly narrow frontal bone with a narrower skull over all. It was probably smaller than P. mongoliensis, with a longer skull and tail proportionally.
P. ordosensis was also found in Mongolia, from a nearly complete skeleton and three other specimens. It, like P. neimongoliensis, was found in the Eijnhoro Formation. It had ver prominent jugal horns and was the smallest known species, and is potentially a nomen dubium. P. mazongshanensis was found in Gansu Province, a location near the border with Inner Mongolia. Its skull was damaged in transit, making it hard to characterize. It had a long snout compared to other species, and a prominent bony protuberance on the upper jaw.
P. sibiricus, shown above (fourth picture), was found in Kemerovo in Siberia, making it one of the most northern species of the genus. It is the largest known species of the genus, which may be due to its northward location, the large size giving it more body heat in colder temperatures. It had quite a few horns around its eyes, with three on each postorbital and one in front of each eye, as well as prominent horns on the jugal bone, and a flange on the lower jaw.
P. lujiatunensis was found in China, in the Yixian Formation in Liaoning. It was contemporaneous with another psittacosaurid, Hongshanosaurus, which was found in the same beds. It had fossa in front of th eeye like in P. mongoliensis and jugal bones that flared outwards widely, like in P. sinensis. It had quite a few primitive characteristics compared to other species of the genus, and was potentially the most basal species. P. major and P. houi are considered junior synonyms of the species.
And finally, P. gobiensis was found in Inner Mongolia, and was very small bodied, and it had many minor differences from the other species. It had a pyramidal horn on the postorbital, a depression in the postorbital-jugal contact, and thicker enamel. It also lived alongisde P. mongoliensis.
There are many other Psittacosaurus specimens not assigned to a genus, making this animal extremely numerous and fascinatingly diverse. There is a lot more to learn about this animal, and I encourage you all to read up on your own!
Shout out goes to klipty!