Taxonomic Revision and Intraspecific Variation Among Early and Middle Eocene Rodents from the Green River Basin, Bighorn Basin, and Lost Cabin of Wyoming
Name: Brieanne Oehlke Year of Graduation: 2010 Hometown: Fremont, WI Major: Biology (Biomedical Science) Minor: Chemistry
Name: Dr. Deb Anderson, Associate Professor of Biology Research Specialty: Paleobiology
Ischyromyids are some of the earliest rodents to show up in
the fossil record. Many of them lived
from the Early to Middle Eocene (55-52 mya) in the Bighorn Basin
and Green River Basin of Wyoming. Being
some of the first rodents to evolve, their molar crown pattern is simple (i.e.
four cusps with cingula and some crests), yet distinctive. Over time, minor changes in the crown pattern
occurred, producing a number of new rodent species. Since the ischryomyids are the base group,
the molar crown pattern for other rodents can be derived from the basic four
cusp pattern. This makes it difficult to
differentiate among species within the family Ischyromyidae. This project works to clarify the taxonomic
classification of Paramys delicatus
and P. delicatior, which are common
species found at both the Bridger and Willwood formations of Wyoming.
In the past, workers have reported new specimens of these taxa, but have
not compared the populations to look at geographic and intraspecific variation
among them. By documenting these two categories of variation, we can clarify
the alpha taxonomy of these two species, making them more useful for future
The ultimate goal of this project is to:
Revise the alpha taxonomy for Paramys
delicatus and Paramys delicatior.
(2) Describe size and/or morphological changes in
crown pattern over time.
(3) Document geographic variation in the two
The major reason I became interested in undergraduate
research was make myself more competitive when applying to Dental Schools. I had known since I was in high school that I
wanted to be a dentist. When I started
my Freshman year of college I was finding ways to do anything I could to build
my resume. By my Junior year the one
thing I was lacking was being involved in research. I had Dr. Anderson for General Biology II my
sophomore year and knew that she was doing research on rodent teeth; I did not
know any details or what the research was about, but I knew I wanted to be a
part of her research specifically. I
knew there were other research opportunities I could have engaged in, but I was
immediately interested in research involving teeth. I knew this would be beneficial for not only
my career, but also for learning research techniques as an undergrad.
From this research on rodent teeth I have learned so much in
a short amount of time. I have learned
that slight differences in molar size and morphology can really make a
difference when differentiating between two different species. I have learned different terminologies for
the shape of a tooth or molar and the different cusps and characteristics that
different molars have, which can be very helpful for my future at dental school
when I'm learning about human teeth. Through
this research I feel more confident in my ability to go through readings and
grasp the main idea that the author is trying to convey, I am advanced in
taking measurements of teeth and being able to compare those measurements and
qualitative data with other rodents, and I am also more confident in my overall
ability to conduct research.
What I value most about my undergraduate research experience
is the fact that I got to participate in something more than just the usual
lectures and labs that every other biology student
does. I got to participate in something
that has not been looked at since 1962 by any one person around the world and
that is something really rewarding to be a part of. This research has helped me to prepare for
dental school and my career by giving me extra knowledge about teeth that I
would not have known about otherwise.
This experience contributed to my knowledge and understanding of
mammalian dental morphology and variation.
Lastly, the hands on experience is the best way to learn the scientific
process, and the interaction between student and faculty allows for students to
be guided while experiencing the gains and hardships of conducting research.
Professor Deb Anderson
While working towards revising the alpha taxonomy of the
genus Paramys, a fossil rodent genus
of the Ischyromyidae, Brie and I discovered a size change in each of the two
sympatric species we are focusing on: Paramys delicatus and P. delicatior.
Specimens of the two species from both the Bighorn and Bridger Basins increase in size over time,
coincident with cooling of the local climate.
By documenting this size change in specimens from two distinct
geographic regions, Brie and I are facilitating taxonomic identification of
specimens recovered in the future. Brie
is very insightful in her approach to identifying significant qualitative features
of the molars. This work is being
supported by a grant from the Student-Faculty Endowment Fund. Our results will be presented at the 2010 Day
of Celebration at St. Norbert College.
“What I value most about my undergraduate research experience is the fact that I got to participate in something more than just the usual lectures and labs that every other biology student does. The hands on experience is the best way to learn the scientific process, and the interaction between student and faculty allows for students to be guided while experiencing the gains and hardships of conducting research.”