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Pachyrhinosaurus canadensis is one of several Pachyrhinosaur species that lived in the high arctic of Canada and Alaska during the Late Cretaceous. While it was slightly less frigid at the time than it is now, winters were still dark and snowy. No fossilized Pachyrhinosaurs have preserved quills, but we do know that their ancestors were quilled, and it isn't beyond reasonable speculation to suspect that it may have had quills, possibly modified into something like a furry coat, in order to help it maintain body temperature during the winter. We also still don't know what these or other arctic herbivores ate during the winter - they may have migrated, some of them, but some fossils of this species were buried during spring snowmelt floods, suggesting that if they did migrate out of the snowy areas, they would have come back fairly early in the season.
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Psittacosaurus mongoliensis is, like Edmontosaurus, one of those dinosaurs we thought we knew everything about until recently. There are actually at least ten species of Psittacosaurus known, and many are known from very complete skeletons. These are the predecessors of the horned Ceratopsians - hornless and frilless, bipedal, but beaked and herbivorous like their descendants. Skin impressions show similar skin to the Ceratopsians, with many hard round scales covering the body. But in 2002 a well-preserved individual was found with long quills attached to the tail. Whether these are related to the quills of feathers, or whether they're an entirely different sort of structure, is still unknown - they may be for display, or they may have, as some have speculated, supported a fish-like fin if that species of Psittacosaurus was somewhat aquatic. If they were related to feathers, then it opens up the possibility for other Ceratopsians to have body feathers as well, and suggests that the ancestor of all dinosaurs (or even further back, the ancestor of many archosaurs) might have been covered in fuzzy protofeathers like many early dinosaurs and even pterosaurs were.
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Einiosaurus procurvicornis is a Cretaceous ceratopsian from Northwestern Montana. What is today plains, forests, and high mountains was then something remarkably similar, though lower in altitude - while so many dinosaurs we've found are from warm, wet places, Einiosaurus lived in a semi-arid temperate zone. We have fossils of juveniles and adults which give researchers a good idea of how the frill and horn developed over the course of the animal's life.
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The Chasmosaurs, including Chasmosaurus belli, are a large group of gigantic ceratopsian dinosaurs from Cretaceous North America (with only one known exception from China). While some ceratopsians have large, elaborate horns, Chasmosaurus only had a few small ones above the nose and eyes and around the edges of its frill, while the frill on Chasmosaurus was one of the largest known for all ceratpsian dinosaurs. This suggests that rather for defense against predators, the frill was used for display, and may have been boldly patterned and colored for attracting mates.

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Lauren Helton

September 2014

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