The cheekbone case: Note from an article about a new ceratopsian

Well… it was new in 2006… but I read the article not long ago, and first now thought of what it means.

The discovery was a fairly complete specimen of a new primitive ceratopsians, named Yinlong downsi (gen. et sp. nov., which is short for new genus and species, in latin… and, again, it was new when the article was published). The article A basal ceratopsian with transitional features from the Late Jurassic of northwestern China describes the find and attempts to place it within a larger context. From what I gathered when reading it, the article proposes two main ideas, apart from describing the fossil, but only one of has a bearing on the cheekbone case.

The thing about the ceratopsians is that their heads evolved ‘forward’ into a more specialised form, while their bodies evolved ‘backward’ to a more basic body plan. Based on some advanced analysis of the sequence the characters were developed within the Ceratopsia, the authors suggest that they developed their specialised skull form before their bodies evolved into a more primitive shape.

The key word here is before, though. Regardless of in which ‘direction’ they evolved, the point is that the skulls developed earlier. It means that they became what they became because their heads started changing to suit their environment. The body changed appropriately too, but it followed later.

I interpret this as emphasising that the skull is indeed the important feature of the ceratopsians. And, the peculiar jugal (cheekbone) protrusion is one of the first skull features they evolved! It seems it was there from the very beginning, and perhaps was one of the things that made them gradually more and more successful, until rivalled only by one other group of dinosaurs, the hadrosaurs (duck-billed dinosaurs).

Sadly, the article does not go into any detail about the jugal of Yinlong, so it has not done much more than further spur my conviction that that bone played a significant role in making the ceratopsians what they were.

However, I have finished reading another scientific article, one that goes into detail about the skull form and function of another basal ceratopsian, Psittacosaurus gobiensis. It is much more important for my cheekbone investigation, but also very complicated, and, as usual, not directly meant to be relevant, so I need to pick out the evidence and puzzle them together in a way that helps me understand just what it means. That will be for the next time…!