Hell Creek fauna - short introduction

Recently there was, and still is, a lot of debate regarding the taxonomic status of some dinosaur genera from late Maastrichtian stage (sometimes called Lancian, after the Lance formation, Wyoming) of North america. Basically, as most of you probably know, Jack Horner, David Evans and some other prominent paleontologists basically proposed that all Pachycephalosaurids (well not all, but I´ll get to that), Hadrosaurs and Ceratopsids of the Hell Creek, Lance and other contemporaneous formations could be lumped into three genera : Pachycephalsoaurus, Edmontosaurus and Triceratops.This wasn't, and still for the most part isn't, univerasally accepted. Then there is also Thomas Carr, who sixteen years ago synonymized Nanotyrannus lancensis with Tyrannosaurus rex. Also, some other taxa and groups from HC formation seem to be a mess, for instance ornithomimids and nodosaurids. And it's not only the big dinsoaurs; most of the small theropods from the HC formation are based on teeth or very fragmentary remains, so indetification can sometimes be very difficult.

My point is that the whole Hell Creek taxonomy is a mess right now. Taxonomy is important, because it has direct impact on the possible reason why dinosaurs went extinct. If dinosaur biodiversity was geting reduced at the end of the Cretaceous, then something was probably happening with their environment just before the K/Pg mass extinction, and that something might have been a reason why that extinction was so devastating. On the other hand, if dinosaurs still flurished during the Lancian in simmilar numbers as during, for instance, Campanian, then the factors that led to their extinction might be very diffirent. Late Maastrichtian dinosaur taxonomy needs to be revalueted, looked more into detail in one big or series of smaller documents. And I would like to do something similar. I was reading about this subject for quite some time, and I find it very frustrating that there is no source that sums up this issue clearly, yet at the same time not to vaguely. Which is why I intended to make a series of post that discuss this particular topic. My goal would be to make it so that if someone is interested in this topic, they could just open my blog and find a lot of information in a single place. I also intend to put as many refferences to my sources as possible. I am not a paleontologist (although I have intentions of becoming one), so most of this should be taken as my oppinion, but I will try to make it as accurate and as educational as possible.

I will start with the taxonomy of ceratopsians, then Pachycephalosaurs, Hadrosaurs and Ankylosaurs. After that, I will write about Tyrannosaurs, then small bird-like therpods and I will end with a single post about Oviraptosaurs, Alvarezsaurs and Ornithomimids. I should note that this is a list of strictly non-avian dinosaur, as I lack apropriate knowledge in Maastrichtian birds. I will try to stick with specimens that are held in public institutions.

I hope that you will find my posts educational and helpful, and that you will enjoy reading them. I would also like to encurage disscusion in the coments.