Pachyrhinosaurus (“thick-nosed lizard”) has become one of the more recognizable ceratopsian names in the last couple of decades, but its remains have actually been known for over 70 years, first discovered in the mid-1940s.
Three different species have been named within the genus, all living about 74-69 million years ago in Alberta, Canada, and Alaska, USA. The type species P. canadensis dates to roughly the middle of that time span, at an age of around 71 million years.
It was one of the largest of the centrosaurs, with the biggest specimens estimated to have measured up to 8m long (26′). Thousands of fossils have been found in a bone bed that seems to represent a mass mortality event – possibly a herd caught in a flash flood – with ages ranging from juveniles to adults.
Rather than horns, Pachyrhinosaurus had huge flattened bosses on its skull, which nearly grew together into a single large mass in both P. canandensis and the younger species P. perotorum. The older species P. lakustai instead had more separated bosses and a “unicorn horn” on its forehead.
(I’m also hardly the first person to speculate about fluffy pachyrhinosaurs, but since they lived in a chilly Arctic environment it’s certainly an interesting possibility.)