The Late Cretaceous and Paleogene span an interval marked by tremendous changes in global climate and terrestrial faunas. My research focuses on the anatomy, systematics, biostratigraphy, and biogeography of Late Cretaceous through Paleogene fossil vertebrates to interpret their evolutionary history. The hub for much of this work is the San Juan Basin of northwestern New Mexico where an incredibly rich and diverse vertebrate fauna.
Late Cretaceous (Campanian) Vertebrates
Near the beginning of the Late Cretaceous, the earth underwent a rapid increase of global temperature that was accompanied by a global rise in sea level. The San Juan Basin contains a long and nearly continuous record of Late Cretaceous time. For much of this interval, New Mexico straddled the western shore of the Western Interior seaway. As global sea level rose and fell, the shoreline alternately moved landward and seaward, at times submerging the landscape or leaving it high and dry.
San Juan Basin contains a diverse vertebrate fauna of including mammals
and dinosaurs. My collaborative work investigates some of these animals
their evolutionary history and Late Cretaceous vertebrate diversity and
Publications resulting from this research and suggested reading
K-PG boundary and Post-Extinction Ecological Recovery
of this work was in
collaboration with my colleague and friend Anne Weil (
The mass extinction event at the end of the Cretaceous is the youngest of the “Big Five” mass extinctions in Earth’s history. It marked the extinction of non-avian dinosaurs and other animals and approximately 50% of mammalian lineages, resulting to profound restructuring of terrestrial ecologies.
of the lineages of
earliest Paleocene mammals that appear soon after the K-PG mass
not known from the latest Cretaceous of North America. However, until
the only record of latest Cretaceous mammalian faunas was
restricted to the northern region of the Western Interior. The
part of this study, we carefully examined the Naashoibito Member,
Kirtland Formation. This stratum is relatively thin and is well-exposed
over a small geographic area of the
Here are some of the results of our study:
recovered a significant
mammal fauna from the Naashoibito Member. The mammalian fauna includes
first diagnostic therian mammals reported from the Naashoibito Member.
documented the presence of the metatherian mammal Glasbius, a taxon
known only from latest Cretaceous faunas of
part of our study, we
examined older Cretaceous (Campanian) strata of the Fruitland and lower
Kirtland Formations (link to research on Late Cretaceous faunas) and
early Paleocene fossil localities of the Nacimiento Formation (link to
on early Paleocene faunas). This resulted in the better understanding
stratigraphic distrubition of animal and plant taxa in Late Cretaceous
Paleocene strata of the
incorporated many of the
results of our study in a permanent exhibit at the New Mexico Museum of
History and Science, “The Cretaceous Seacoast Exhibit.” We also
American undergraduate students from
The explosive diversification of mammals at the beginning of the Cenozoic was one of the most important events in mammalian history and is considered a classic example of an evolutionary radiation. After the mass extinction of dinosaurs and other organisms at the Cretaceous-Paleogene (K-Pg) boundary, mammals underwent a dramatic radiation that resulted in a rapid increase in species diversity, morphological disparity, and ecological diversity (Alroy 1999, 2000a, b; Archibald, 1996; Rose, 2006; Stucky, 1990). However, the record of this diversification is poorly documented, especially at its beginnings in the early Paleocene when rates of taxonomic and morphological change are expected to be at their greatest.The Nacimiento Fm. is the most diverse, longest, and most complete record of early Paleocene eutherian mammal succession in the world, spanning nearly four million years. Importantly, this record can be tied to the time scale using paleomagnetostratigraphy and radiometric dating.
have long been interested
in the taxonomy, phylogeny, and evolution of early Paleocene therian
and early Paleocene mammalian biostratigraphy and biochronology. I am
collaboratively with other workers including Stephen Brusatte (Ph.D.