From the Community: From Bonebeds to Paleoecology

Editor Note: Hi guys, Sarah here! I read this post over at the Extinct Blog about a month ago, and found it a great informative read by guest blogger Don Brinkman from the Royal Tyrrell Museum in Drumheller, Alberta. I wanted to bring it to the attention of the PLOS Paleo Community, so with the permission of the folks over at the Extinct Blog, I am posting a snippet of the article here, and encourage you to follow the link at the end of the post to read the fascinating article in its entirety. 

I [Don Brinkman] started at the Tyrell Museum in 1982. Back then, the dinosaur renaissance was in full swing. The public were clearly interested in understanding dinosaurs as living animals: they wanted to know how dinosaurs lived and interacted with one another, what they ate, and what their lives were like. And the Tyrrell’s approach to research was to be organized similarly: we were to undertake field work and research with a paleoecological focus. But there was a problem: while we had good phylogenetic methods which allowed us to understand the ancestry of dinosaurs, paleoecology was still viewed as little more than speculative story-telling. Our challenge, then, was to work out how to understand dinosaurs as living organisms in long-gone environments without foregoing scientific care or rigor.

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Badlands of Dinosaur Provincial Park, taken from the air. This area is now a natural preserve, and only accessible by guided tour or permit.

One approach was already underway when I joined the team.  This was the study of bonebeds in Dinosaur Provincial Park. Virtually no field work had been done in the park between the mid 60’s and the late 70’s, the time during which the Dinosaur Renaissance had taken place. This is partly because paleontological work in the province during this time was focused primarily on non-dinosaur vertebrates, particularly mammals and fish, and partly because the park administrators felt that their job of preserving the fossils present in the park was best done by preventing any excavation.  However, dinosaurs from the park were in many of the museums and research institutes in North America and around the world, and much of the contemporary dinosaur knowledge was based on these specimens.  So any paleoecologically-based studies that involved dinosaurs from Dinosaur Provincial Park relied on these museum specimens.

One kind of study that was undertaken focused on taphonomy, which is what happens between the time an animal dies and is preserved as a fossil.  A survey had been undertaken of specimens in museum collections, and it was found that while in most of the fossil bearing formations of the western United States, like the Morrison Formation, dinosaurs were represented by isolated elements, most of the specimens from Dinosaur Provincial Park were articulated skeletons (Dodson et al. 1980).  This gave the impression that there was something unusual about the formations exposed in the park leading to the preservation of complete skeletons.  So this is what Phil Currie was expecting to see when he started doing field work in the park in 1979.

Phil Currie in the early 80’s using surveying equipment to map bonebeds.

However, it didn’t take him long to realize that it wasn’t that there was a preferential preservation of articulated skeletons. Rather everything was more abundant.  The dominance of articulated skeletons in museum collections was because of a collecting bias toward complete skeletons, whereas isolated elements were left behind. This was perfectly understandable when the goal of collecting was to provide material for taxonomic studies and to build museum exhibits.  Currie also realized that isolated elements were not randomly scattered through the beds. They tended to occur in distinct layers, sometimes very concentrated.  These concentrations were referred to as bonebeds. He felt that by studying bonebeds using the approaches to taphonomy that had been developed, information about the communities and environments at the time the dinosaurs were living (ie., paleoecology) could be obtained.

One way that he thought that data from bonebeds could contribute to paleoecological studies was by providing insight into the relative abundance of animals in the original community. The bonebeds were mixed and transported assemblages, but it was assumed that the abundance of an animal in the bonebed should be a reflection of the abundance of the animal in the original community.  The taphonomic processes leading to bonebeds are different from the taphonomic processes leading to preservation of articulated skeletons, so this could be tested by comparing the abundance of an animal in a bonebed to the abundance of that animal as an articulated skeleton.  This test could be done because of the high number of articulated skeletons that had been collected (over 300 at the time) and a system of marking quarries that had been initiated in the ‘30s.  Phil Currie started by mapping bonebeds and recording what was seen on the surface, particularly the kinds and relative abundance of taxa.

A pattern soon emerged.  Hadrosaurs were, by any measure, the most abundant kind of dinosaur present, usually around 60%.  Ceratopsians and carnivorous dinosaurs constituted another 10% each.  The remaining 20% consisted of a variety of herbivorous dinosaurs. There were exceptions to the pattern – pachycephalosaurs were more abundant as isolated elements than they were as articulated specimens, but this was easily explained because of the high preservation potential for the skull caps.   More intriguingly, there were examples of bonebeds that were unusual in being dominated by the remains of one kind of dinosaur that was otherwise rare in the community.

And the dinosaur was always a ceratopsian.

Find out why….read the rest of this blog by following the link below.

From Bonebeds to Paleoecology — Extinct.

Source: From Bonebeds to Paleoecology — Extinct

Published by Sarah Z. Gibson

Dr. Sarah Z. Gibson is a paleontologist and science communicator based in Minnesota. Her research focuses on the evolutionary history of ray-finned fishes from the Early Mesozoic.

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