Mammals in Montana: the birth of modern mammal communities
small mouse. Note the scale bar. These very small fossils require hours of
crawling the outcrop with eyes wide open.
This changing ecosystem is what I try to understand. We have a pretty good idea of what this time period was like in the Great Plains of Nebraska, South Dakota and Wyoming. We also know much from the rich fossil record of Oregon; but the picture is much dimmer when it comes to the northern Rocky Mountains. Fortunately, in the 1970s, the work of Donald Rasmussen (and others before and after him) brought to paleontologists’ attention the Cabbage Patch beds of Montana. This series of fossil-bearing rocks located about one hour east of Missoula is an opportunity to explore a region geographically intermediate between the better known records of Oregon and Nebraska. Studying the Cabbage Patch beds and contrasting them to the Oregon and Nebraska records will help understand how varied mammalian faunas were across North America and provide insights into the assembly of modern mammalian communities.
We were not the only ones prospecting. At this same locality,
almost under the foot of this fawn, we found oreodonts,
which are distant relatives of deer.
Although much fieldwork has been previously undertaken in the fossil-bearing layers of Cabbage Patch, a lot remains to be done to collect enough fossils (and data on their geological context) to paint a fuller picture of the ecosystem of the place around the Oligo-Miocene boundary (23 million years ago). With that in mind, I undertook a month of fieldwork last summer to collect additional fossils and consider their preservation and depositional environments.
With the help of two undergraduate students from the UW Biology department and welcoming landowners, I was able to collect many fossil bones, teeth, and shells as well as hundreds of pounds of sediment containing fossils to screenwash on campus (over 1500 lbs.). The main goal of this year’s work was to relocate a number of localities and assess their productivity. The other goal of the field season was to collect some data on the nature of the rocks containing the fossils.
Thien-Y Le, graduate of the department of biology, wrapping some fossils
near a very productive locality where she had just found some dog teeth.
We also were able to collect – with the help of Dr. Caroline Strömberg and PhD candidate Elisha Harris, their crews, and collaborators – some rock samples that will help us understand the habitats in Cabbage Patch at the time. These samples will be used to determine the kinds of plants present and the climatic conditions around Drummond (MT) 28 to 23 million years ago.