Tag: ornithischia

Ceratopsian Month #02 – Psittacosaurus sp.

Living during the Early Cretaceous (~126-101 mya) in Mongolia, Siberia, and China, Psittacosaurus (meaning “parrot lizard”) represents an early specialized offshoot of the ceratopsians – it wasn’t directly ancestral to any of the later forms, instead being more of an evolutionary cousin.

It’s one of the most well-studied of all non-avian dinosaurs, represented by hundreds of fossils at all ages from hatchlings to adults. A large number of species have been named within the genus, although there’s disagreement about how many are actually valid, and even some of the best-preserved specimens still haven’t been given an official species classification.

Growing up to about 2m long (6′6″), it had sideways-flaring cheek horns and little-to-no frill, and only four fingers on its hands instead of the five seen in all other ceratopsians. One fossil preserves an amazing level of soft-tissue detail, showing the outline of the body, a row of long bristles, skin membranes running from its ankles to the base of its tail, and even evidence of the countershaded color pattern the animal had in life.

While adults were fully bipedal, hatchlings and juveniles seem to have moved around on all fours – suggesting that some of their direct ancestors may have evolved to be quadrupedal before secondarily re-acquiring two-legged locomotion.

Ceratopsian Month #01 – Yinlong downsi

It’s time for another month of themed blog posts, and this August features one of the most iconic groups of dinosaurs: the “horn-faced” ceratopsians!

Existing for almost 100 million years, from the Late Jurassic all the way up to the K-Pg mass extinction, ceratopsians originated in Asia and were part of a group called marginocephalians, sharing a common ancestor with the closely related pachycephalosaurs. The earliest members barely resembled their more famous descendants, lacking showy headgear and looking more like fairly generic basal neornithischians – but by the time of the Late Cretaceous their descendants had migrated across to North America and evolved into large quadrupeds, with some forms like Triceratops being so incredibly common that they must have been the dominant herbivores in their environments.

So let’s start right at the beginning of the group with…

Continue reading “Ceratopsian Month #01 – Yinlong downsi”

Unsolved Paleo Mysteries Month #16 – Strange Snoots 2: Oddball Ornithischians

Those extinct horses weren’t the only ancient creatures with unexplained noses. Some dinosaurs had equally weird things going on with their snouts – and while hadrosaurs’ big honkin’ snoots are fairly well-known, there were other ornithischians with their own bizarre nasal anatomy.

An illustration of the skull of an extinct horned dinosaur, showing the unusually large nasal cavity. Below is a reconstruction of the dinosaur's head in life.
Triceratops horridus skull and head reconstruction

Many ceratopsids had an enormous nasal opening forming a giant bony “window” through their snout, with the chasmosaurines like the famous Triceratops having additional bony projections and hollowed regions within these holes. They probably supported some huge elaborate cartilage structures in life, but what they were for is still a mystery. They may have helped with heat dissipation or moisture conservation, aided sound production, provided a highly sensitive sense of smell, housed a vomeronasal organ, held part of an air-filled pneumatic system… or, getting more speculative, possibly even some sort of inflatable nasal display structure.

An illustration of the skull of an extinct armored dinosaur, showing the multiple holes inside the nasal cavity. Below is a reconstruction of the dinosaur's head in life.
Minotaurasaurus ramachandrani skull and head reconstruction

Some ankylosaurids, meanwhile, went with multiple holes instead. Minotaurasaurus here had two additional openings around its nostrils, and Pinacosaurus could have up to five – the purpose of which is unknown. Many ankylosaurs also had forward-facing nostrils (a rare trait in archosaurs) and incredibly complex looping airways through their skulls. These may have allowed for mammal-like “air conditioning”, regulating the heat and moisture content of each breath, or perhaps enhanced their sense of smell or served some sort of resonance chamber function. Or, again, maybe even nose balloons.

Also floofy ankylosaur because I can.