Episode 92 is all about Psittacosaurus, a hadrosauroid from Italy whose holotype has the nickname “Antonio.”

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In this episode, we discuss:

• The dinosaur of the day: Psittacosaurus
• Name means “parrot lizard”
• Ceratopsian that lived in the Early Cretaceous in what is now Asia (Mongolia, Siberia, China, and maybe Thailand)
• Earliest known ceratopsian
• First discovered in 1922 during the American Museum of Natural History’s third expedition to the Gobi Desert. They found a nearly complete skull
• First described in 1923 by Henry Fairfield Osborn
• Type genus of the family Psittacosauridae, which Osborn named in 1923
• One of the most well known dinosaurs, with more than 400 individuals found (lots of complete skeletons, and a wide variety of ages)
• 17 species have been named Psittacosaurus, but only 9-11 are considered valid (highest number of valid species assigned to a non-avian dinosaur genus)
• Type species is P. mongoliensis
• Type specimen of P. mongoliensis is of a juvenile
• Different species have different skull shapes (length, height, roundness, and bony lumps)
• Species include mongoliensis, lujiatunensis, neimongoliensis, xinjiangensis, sinensis, meileyingensis, ordosensis, sibricus
• Osborn also named another specimen Protiguanodon mongoliense, thinking it was an ancestor of Iguanodon. But it turned out to not be different enough from Psittacosaurus, (Osborn said it had different teeth and snout features), and in 1958 Yang Zhongjian, a Chinese paleontologist, renamed it to Psittacosaurus protiguanodonensis, though nowadays it’s usually considered to be Psittacosaurus mongoliensis and Protiguanodon and Psittacosaurus protiguanodonensis are considered to be junior synonyms of P. mongoliensis
• C.C. Young named a new species, P. osborni, in 1931 after Henry Osborn (partial skull found in Inner Mongolia). Some think it’s a synonym for P. mongoliensis, others think it’s valid.
• Psittacosaurus sibiricus had some bony horns, but it’s thought to be convergent evolution
• Psittacosaurus mongoliensis skulls are flat on top
• P. sinensis have smaller skulls than other Psittacosaurus and have fewer teeth than P. mongoliensis. Also, the cheek bones flare out sideways that look like horns and the skull is wider than it is long. Also has a smaller “horn” behind the eye (also seen in P. sibiricus)
• P. xinjiangensis has a cheek horn that is flattened on the front end
• P. meileyingensis has the shortest snout and shortest neck frill, and a very round skull
• P. neimongoliensis has a narrow skull compared to other species and is the smallest known species
• P. lujiatunensis is well known from a study of three specimens in 2007. Had an advanced brain, may have had behavior as complex as Tyrannosaurus (may have built nests, cared for young, and slept like birds)
• Did not have much ornamentation (elaborate horns or neck frills) but some had bony lumps that grew from their skulls
• Had four digits on the hand, instead of five, like other ornithischians and ceratopsians, and four toes, similar to small ornithischians
• Up to 6.5 ft (2 m) long, and weighed up to 44 lb (20 kg)
• Body had scales, large and small, in irregular patterns
• In 2008 a study of two different Psittacosaurus individuals found that its skin was thick (about 40 layers) and may have helped protect against predators
• In 2010, Ford and Martin said Psittacosaurus may have been semi-aquatic, swimming with its tail like a crocodile. This is based on specimens being found near lakes, long chevrons in the tails (bristles on tail may have helped form a fin), and the position of the nostrils and eyes
• Had a proportionately large brain, so probably had complex behaviors
• Good sense of smell and vision, and may have been cathemeral
• No direct evidence that they cared for their young, but may have happened
• Quadrupedal as a juvenile
• Between ages 4-6, their legs grew an they became bipedal
• Could not rotate or reach the ground with its forearms
• In 2007 Phil Senter did a study of P. neimongoliensis and P. mongoliensis and found its forelimbs were too short to reach the ground (55% as long as the hindlimbs) so they were bipedal. Also too short to dig and bring food to the mouth
• They had parrot-like beaks and cheek teeth to eat fiberous vegetation
• Had a tall skull that was short in length, and in some cases is almost round
• Probably a selective browser
• Had a beak, probably covered in keratin (used to crop vegetation to eat)
• Had self-sharpening teeth to crop and slice vegetation (could not grind or chew food, used gastroliths)
• Upper and lower jaws in the skull worked like a single unit, without internal joints (akinetic skulls); had only one joint in the jaw joint, so it could slide its lower jaws forward and backward to shear food
• Juvenile Psittacosaurus not found with gastroliths, so its possible its diet changed with age (less fibrous at first)
• P. gobiensis was found to have lots of gastroliths in its gut, so it may have used its beak to crack nuts and seeds and use the stones to help digest
• Was a prey animal. One juvenile Psittacosaurus‘ remains are found in a carnivorous mammal (first known example of a mammal that ate a dinosaur)
• A herd of 6 Psittacosaurus were found buried by a volcanic mudflow and shows that they possibly lived in groups (they were different ages). The young ones had worn teeth, which means they chewed their own food. They probably lived together for protection, to help with finding food, or possibly helping with the nest
• In 2004, 34 juvenile Psittacosaurus skeletons and the skull of an adult were found in the Yixian Formation. All the juveniles are under the adult, which may mean the adult was caring for the young. But in 2013 it was pointed out that the adult didn’t belong with the nest and had been glued onto it, and the adult was actually 6 years old (wouldn’t reach maturity until age 10). Also unlikely that one adult would have so many juveniles at once
• In 2014, a study of the 6 year old found that there may have been “post-hatching cooperation” so it may have been taking care of the babies. Some modern birds do this
• Hatchlings have been discovered, including one at the AMNH that’s 4-5 in (11-13 cm) long and one also at AMNH that’s 1.8 in (4.6 cm) long. They’re both P. mongoliensis and from Mongolia
• Quill like feathers on the tail
• One was found with long filaments on the tail
• Bristle-like integumentary structures were found at the tail of a Psittacosaurus found in China (probably the Yixian Formation) in 2002, (may have been used for display). Not assigned to a species, but was illegally taken from China and purchased by a German museum, and then described while awaiting repatriation. They had the same fluorescence as scaled in ultraviolet light, so may have been keratinized
• One Psittacosaurus had a pathology. It’s P. mongoliensis, found in the Yixian Formation. It had an infection near the mid part of the right fibula. It has a large round pit, from lack of blood supply and has large swelling along the lower part of the bone. It’s unclear how this happened
• Ceratopsia is a group of herbivorous dinosaurs that lived in North America and Asia in the Cretaceous
• They had parrot-like beaks and cheek teeth to eat fiberous vegetation
• They were ornithiscians
• Also had a frill (used for defense, regulating body temperature, attracting mates, or signaling danger)
• Probably traveled in herds and could then stampede if threatened
• Fun fact: 
  

  Egg	Weight	Size	Size relative to chicken	calories	fat	Protein
  “USDA Large” Chicken egg	Avg 2 ounces (57g)	46cc	1	90	6g	7g
  Ostrich Egg	Typically ~3 pounds (1.4Kg)	~1,100cc -> Circum=15.8” (40cm)	~24	~2,000	~150g	170g
  The Largest Dinosaur Egg (I could find) Oviraptorosaur From China		>60cm L x >20cm D -> ~18,000cc	~400	Asum’d ratio 36,000	Asum’d ratio 2,400g	Asum’d ratio 2,800g
  Quail Egg	~9g (.3oz)		Less than 1/5	14	1g	1.2g

  Despite ostrich eggs being the largest they are apparently the smallest in proportion to the bird laying them. Ostriches lay about 50 a year, equivalent to 1,200 chicken eggs or 3 giant oviraptorosaur eggs, all equivalent to about 2 dozen chicken eggs a week.

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