I am a vertebrate paleontologist with an interest in paleoecology, the study of interactions between organisms, other organisms, and the environment in the fossil record. I am especially interested in how physical environmental factors (such as volcanism or climate change) drive vertebrate evolution.
My PhD research
focuses on the influence of climate on mammalian evolution during the
late Oligocene and Miocene. In particular, I am interested in
determining whether
periods of climate change triggered corresponding changes in body size
in North American mammals. The Oligo-Miocene is an ideal natural laboratory in
which
to study the biotic response to climate
change because it encompasses periods of both global warming (26-23 & 17-15 Ma)
and global cooling (15-5 Ma). The classical ecological model
of
body size patterns in extant animals (Bergmann's rule) holds that
temperature is the most important determining factor, but it has
since been suggested that other climatic and biotic variables may play
significant, or even predominant, roles as well.
Understanding
which of these factors have driven body size evolution in the past will
allow a more detailed understanding of the mechanisms underlying
Bergmann's rule and may allow more robust predictions of the effects of
anthropogenic global warming.Previous
Research
The Jurassic-Cretaceous (J-K) boundary, which marks a relatively minor
mass extinction, was the focus of my masters research at the University
of Bristol. It has long been recognized that the
J-K boundary
marks an ecological shift, especially among dinosaurs, with the
replacement of sauropods and allosaurs by ornithopods and coelurosaurs
(on most continents). However, it has been suggested that
this
apparent change is in fact only the product of an incomplete and
taphonomically biased fossil record. I addressed this issue
using methods developed by Sarda Sahney
and Mike
Benton,
minimizing preservational bias by including data only from
well-preserved and well-studied communities. The results of
this
work suggest that the J-K extinction was a genuine event rather than a
taphonomic artifact. A second, independent project I
conducted at Bristol, along with Emma Nicholls, addressed the
quality of the dinosaur fossil record. Our results suggest
that
the dinosaur fossil record remains very incompletely sampled; this is
the case for all continents, taxonomic groups, and time periods.
As such, any study of dinosaur paleoecology must be taken
with a
grain of salt; it is thanks in part to these findings that I now study
Cenozoic mammals.
My bachelor's research at the University of Chicago was on the basal dinosaurs Eoraptor and Herrerasaurus from the Ischigualasto Formation in Argentina. In particular, I was interested in the running abilities of the earliest dinosaurs relative to other Triassic reptiles. My results suggest that several other members of the Ischigualasto ecosystem were just as adept cursors as Eoraptor and Herrerasaurus. If anything gave the first dinosaurs an edge over other Triassic reptiles, it does not seem to have been their speed.
The Jurassic-Cretaceous (J-K) boundary, which marks a relatively minor
mass extinction, was the focus of my masters research at the University
of Bristol. It has long been recognized that the
J-K boundary
marks an ecological shift, especially among dinosaurs, with the
replacement of sauropods and allosaurs by ornithopods and coelurosaurs
(on most continents). However, it has been suggested that
this
apparent change is in fact only the product of an incomplete and
taphonomically biased fossil record. I addressed this issue
using methods developed by Sarda Sahney
and Mike
Benton,
minimizing preservational bias by including data only from
well-preserved and well-studied communities. The results of
this
work suggest that the J-K extinction was a genuine event rather than a
taphonomic artifact. A second, independent project I
conducted at Bristol, along with Emma Nicholls, addressed the
quality of the dinosaur fossil record. Our results suggest
that
the dinosaur fossil record remains very incompletely sampled; this is
the case for all continents, taxonomic groups, and time periods.
As such, any study of dinosaur paleoecology must be taken
with a
grain of salt; it is thanks in part to these findings that I now study
Cenozoic mammals.My bachelor's research at the University of Chicago was on the basal dinosaurs Eoraptor and Herrerasaurus from the Ischigualasto Formation in Argentina. In particular, I was interested in the running abilities of the earliest dinosaurs relative to other Triassic reptiles. My results suggest that several other members of the Ischigualasto ecosystem were just as adept cursors as Eoraptor and Herrerasaurus. If anything gave the first dinosaurs an edge over other Triassic reptiles, it does not seem to have been their speed.