Ecology of the Hell Creek Formation: Introduction

Although most of the posts so far on Mesozoic Musings have been concerning speculative appearances, an increasingly interesting topic for me has been paleoecology, and in particular, how different species coexisted without competition. This is niche partitioning - how resources (not neccasarily food) are shared between animals by varying what they use in sometimes very small ways. For example, on the African savanna, the big carnivores partition their prey by being adapted to some particular food: cheetahs prefer small antelope, lions like mid-sized animals such as wildebeest, buffalo, and zebra, leopards feed upon a variety of small animals and hoofstock, etc. I should also note that by no means is niche partitioning some kind of rule that stops animals from eating things which doesn't fall neatly into their category. In fact, there's a lot of overlap - but you'll notice if you look carefully, that many animals differ in some way in their diet, and often show specializations towards a particular food source, even if they don't rely on it heavily.

At the moment, I find herbivore niche partitioning particularly interesting, and how we can apply it using educated speculation to prehistoric ecosystems. I'll be doing this quite a lot in the future on Mesozoic Musings, focusing on different formations.

Recently, I've been looking at the ecosystem of the Hell Creek Formation. This is the first ecosystem that I'll be looking at on Mesozoic Musings, so I wanted to start off with what has to be one of the best known formations. Also, bear in mind that the things I'm working on here are still in development - I'm basically thinking aloud here.

First of all, some background information. I'm sure that most people reading Mesozoic Musings will know quite a bit about Hell Creek already, it's pretty well known in paleontology after all, but still, just to set the scene, so to speak.

 Hell Creek during the Late Cretaceous was a moist, mild to sub-tropical area with fluctuating rivers, channels, and deltas. It was at the time on a coastal plane which extended outwards towards the newly-formed Rocky Mountains. 

It was a fairly flat floodplain, covered in forests consisting of small to medium sized trees. The plant life consisted of mostly angiosperms, with some gingkos, some gymnosperms, and a few ferns, horsetails, and cycads. A rather mixed group of plants, notably with 90% of all plant specimens collected consisting of angiosperms.

 By Stickpen - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7163942

These fossilized fruit are known as Spinifructus antiquus, of an unknown family and order, and this specimen has been discovered in Hell Creek.

The plant life really wouldn't have looked so very different from that in a modern day woodland, to the untrained eye.

So the envioroment in a nutshell was moist, forested, and with lots of rivers and maybe swamps. Now, let's take a look at the herbivorous dinosaurs found here.

First of all, here's a study that shows the 8 most common dinosaur families found in Hell Creek:

Ceratopsidae (61%)

Hadrosauridae (23%)

Ornithomimidae (5%)

Tyrannosauridae (4%)

Dromaeosauridae (2%)

Pachycephalosauridae (1%)

Troodontidae (1%)     

While obviously fossils can't be used as very accurate judges of paleopopulations, it can help us to get a good idea of what animals were common and which were rare in the area, especially in a place such as Hell Creek where we have such a wealth of data. I will also refer to more in-depth studies focusing on particular species populations in the upcoming text.

This quick introduction will be followed up upcoming posts on individual species and how they would have fit into the ecosystem of Hell Creek.

Until next time!