CURRENT RESEARCH
Pleistocene microvertebrate communities of the Mojave Desert, southern California
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Images of extant taxa found in the Mojave Desert. Images curtesy of the The Nature Conservancy.
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"It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change" - Charles Darwin, On the Origin of Species
Global climate change is not a future problem. Changes to Earth’s climate driven by increased human emissions of greenhouse gases are already having widespread effects on the environment: shrinking glaciers and ice sheets, more extreme storms, rising sea level, shifting plant and animal geographic ranges, etc. As climate continues to change, it is important to understand how life (organisms and environments) will adapt to change. We can evaluate organismal adaptations to climate change utilizing the fossil record. |
During the Pleistocene, the Mojave Desert was a beautiful floodplain valley with lakes and vegetation. Today, we know it as a desert with freezing cold winters and extremely hot summers. Despite the volatile climate, the Mojave Desert supports a diversity of flora and fauna, especially microvertebrates. Microvertebrates are closely tied to their environment and are particularly sensitive to local climate changes. Thus, making them ideal for answering questions about climate-species dynamics.
I am particularly interested in questions about:
I am particularly interested in questions about:
- Spatiotemporal changes
- Evolutionary rates
- Conservation efforts (present and future)
Past research and Projects
DISSERTATION:
DETERMINING THE CLIMATIC AND ECOLOGICAL EFFECTS OF THE CENTRAL ATLANTIC MAGMATIC PROVINCE (CAMP) ACROSS THE END TRIASSIC MASS EXTINCTION IN THE ELLIOT FORMATION, SOUTH AFRICA AND LESOTHO
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The end Triassic Mass Extinction (ETE) is hypothesized to have been caused by large-scale, volcanically induced perturbations to the global carbon cycle. The Central Atlantic Magmatic Province (CAMP), the volcanic event of interest, covered most of northern Africa, eastern North America, northern South America, and parts of western Europe with approximately 3,000,000 cubic kilometers of basalt flows, making the CAMP the most extensive and voluminous volcanic event on Earth. Mathematical estimations suggest that the CAMP emitted between 8,000-9,000 Gt of carbon as CO2 which impacted global climate causing environmental and ecosystem changes worldwide. |
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Evidence supporting this hypothesis is preserved in the lithologic record of the Elliot Formation, South Africa and Lesotho.
The Elliot Formation, spanning the end Triassic - early Jurassic, is comprised of terrestrial paleosols containing pedogenic carbonate nodules and large fluvial sandstones. The Elliot Formation is rich in both vertebrate body and trace fossils and serves as a global standard for Triassic-Jurassic boundary (TJB) studies. This fossil record includes remains of true dinosaurs, pseudosuchians, lepidosaurs, stem-group turtles, temnospondyl amphibians, and later-branching therapsids. The Elliot Formation is one of the few fossiliferous continental deposits that spans the ETE, which makes this formation crucial for understanding changes in the terrestrial ecosystems of southern Pangaea through the TJB interval.
For my dissertation work, I am:
1) Identifying CAMP volcanism and the ETE in the stratigraphic record of southern Africa
2) Generating paleoclimate data before, during, and after the ETE
3) Creating educational materials for teaching paleoclimate and climate change using C-cycle perturbations
4) Evaluating ecosystem change before, during, and after the ETE
The Elliot Formation, spanning the end Triassic - early Jurassic, is comprised of terrestrial paleosols containing pedogenic carbonate nodules and large fluvial sandstones. The Elliot Formation is rich in both vertebrate body and trace fossils and serves as a global standard for Triassic-Jurassic boundary (TJB) studies. This fossil record includes remains of true dinosaurs, pseudosuchians, lepidosaurs, stem-group turtles, temnospondyl amphibians, and later-branching therapsids. The Elliot Formation is one of the few fossiliferous continental deposits that spans the ETE, which makes this formation crucial for understanding changes in the terrestrial ecosystems of southern Pangaea through the TJB interval.
For my dissertation work, I am:
1) Identifying CAMP volcanism and the ETE in the stratigraphic record of southern Africa
2) Generating paleoclimate data before, during, and after the ETE
3) Creating educational materials for teaching paleoclimate and climate change using C-cycle perturbations
4) Evaluating ecosystem change before, during, and after the ETE
High resolution C-isotope chemostratigraphy of the Elliot Formation of southern Africa
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The Upper Triassic to Lower Jurassic Elliot Formation of the main Karoo Basin in South Africa and Lesotho preserves evidence for a diverse continental ecosystem. Based on detrital zircon geochronology and magnetostratigraphy, this change may be tied to global environmental changes initiated in the Central Atlantic Magmatic Province (CAMP), which has been linked to the end-Triassic Mass Extinction (ETE).
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Chemostratigraphy uses chemical "fingerprints" to correlate rocks and sediment. C-isotope geochemistry is a powerful means of correlating stratigraphic sections around the world to reveal changes in the global carbon cycle. Therefore, C-isotope chemostratigraphy as an additional stratigraphic proxy to identify the end-Triassic Extinction interval as well as the Triassic-Jurassic boundary in the main Karoo Basin. In global records (e.g., Newark and Hartford basins, St. Audrie’s Bay, and Kuhjoch, Austria), the end-Triassic extinction interval is marked by at least one 5 to 8‰ Negative Carbon Isotope Excursion (NCIE) in the δ13C content of organic and inorganic materials from marine and continental (terrestrial and lacustrine) sedimentary rocks.
2021 Geological Society of America Conference talk (recorded video) available upon request! Contact me.
2021 Geological Society of America Conference talk (recorded video) available upon request! Contact me.
Inferring paleoclimate and calculating PCO2 using pedogenic carbonates from the upper elliot formation, south africa
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Stable isotope data from pedogenic carbonate nodules provide quantitative evidence for changes in climate because they precipitate in equilibrium with the atmosphere, recording atmospheric CO2 concentration, and record environmental conditions at the time of formation through meteoric waters. Preliminary results from Upper Elliot Formation (early Jurassic) nodules suggest isotopic change to the source water in which initial precipitation occurred. Sampling more nodules throughout the Elliot Formation will provide better insights about sources of water, environmental changes to water sources, and reveal climate trends across the Triassic-Jurassic boundary.
2019 GeoHog Conference poster available upon request! Contact me. |
Polished nodule from South Africa
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Community response to the End Triassic Mass Extinction in the Elliot Formation of South Africa and Lesotho
The Elliot Formation, which spans the Upper Triassic to the Lower Jurassic in the Karoo Basin of southern Africa, is rich in both vertebrate body and trace fossils and serves as a global standard for Triassic-Jurassic boundary (TJB) studies. This fossil record includes remains of true dinosaurs, pseudosuchians, lepidosaurs, stem-group turtles, temnospondyl amphibians, and later-branching therapsids. The Elliot Formation is one of the few fossiliferous continental deposits that spans the end Triassic Mass Extinction (ETE), which makes this formation crucial for understanding changes in the terrestrial ecosystems of southern Pangaea through the TJB interval. Previous studies of vertebrate diversity in the Elliot Formation have focused on total diversity of the Lower Elliot (LEF) and Upper Elliot (UEF) members across all of southern Africa; however, this is too coarse to observe changes in community structure due to the ETE, therefore finer scale analysis is need to determine how communities changed.
Ongoing project unveiled at 2020 SVP.
For more information, Contact me.
Ongoing project unveiled at 2020 SVP.
For more information, Contact me.
Masters Thesis:
FOSSIL MOLES FROM THE GRAY FOSSIL SITE, TN: NEW INSIGHTS ON THE DIVERSIFICATION AND EVOLUTION OF NORTH AMERICAN TALPIDAE
For my master's thesis, I studied:
1) All talpid taxa at the Gray Fossil Site 2) Relationships between extant and extinct talpid taxa 3) Dispersal patterns between North America and Eurasia |
Talpidae (true moles, shrew moles, and desmans) is an ecologically diverse family that is widely distributed across the northern hemisphere. Talpids are well known for their subterranean lifestyles and unique morphological modifications for fossorial specialization; though, semi-aquatic and terrestrial locomotor ecologies are also common. Even though there are variable locomotor ecologies among extant talpids, convergent evolution strongly influences body shape, creating problems for researchers interested in understanding the evolutionary history and diversification of the family.
I used new fossil occurrences from the Gray Fossil Site in northeastern Tennessee to improve our understanding of talpid dispersals between North America and Eurasia, and help reveal how they have evolved through time. |
2017 and 2018 SVP, and 2018 SEAVP posters available upon request! Contact me.
It's published in Palaeontologia Electronica: https://doi.org/10.26879/1150
It's published in Palaeontologia Electronica: https://doi.org/10.26879/1150
Reconstructing Body Mass from Marsupial Dental Measurements
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Teeth are the most commonly-preserved species-diagnostic mammalian fossil remains, so dental measurements are often used for predicting body mass. Allometric relationships between dental measurements and mass from extant species are used to infer body mass for taxa that cannot be measured directly. While this approach has been widely used for a variety of placental lineages, we applied this concept to marsupials to create a molar area/body mass proxy that accurately predict body mass in both modern and fossil marsupials.
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We used 89 extant species to create the equations, and found that molar area is a good predictor of body mass in extant marsupials. We are confident that these equations can be used to accurately predict extinct marsupial body masses.
Paper in early stage prep.
2016 SVP poster can be provided upon request. Contact me.
Paper in early stage prep.
2016 SVP poster can be provided upon request. Contact me.
New Marsupial Occurrence from Oregon's middle Miocene
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The fossil history of North American (NA) marsupials is quite interesting. NA marsupials are known from the late Cretaceous and went extinct sometime during the early Miocene.
New dental material from a middle Miocene locality in Oregon represents a new occurrence of the extinct marsupial genus, Herpetotherium. This new occurrence suggests that NA marsupials were still around during the middle Miocene. |
This occurrence is being included in the "Eulipotyphlans from the Mascall Formation, OR" paper.
Undergraduate thesis:
EULIPOTYPHLANS from the Mascall Formation, OR
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The Mascall Formation is one of the best-known middle Miocene records in North America; however, it has never been screenwashed, and has a relatively poorly-known microfauna. My undergraduate thesis site, Cave Basin, is one of the few Mascall Formation localities that can be screenwashed and contained abundant microfossils!
Cave Basin has quite a bit of eulipotyphlan diversity:
- 2 erinaceids (moonrats) - 5 soricids (shrews) - 2 talpids (moles) - 1 proscalopid (extinct mole-like mammal) The great diversity of eulipotyphlans in Cave Basin is consistent with Shotwell's suggestion of high levels of habitat diversity in Oregon's middle Miocene. |
Eulipotyphla is a basal order of mammals that contains 4 extant families: Erinaceidae (hedgehogs and moonrats), Soricidae (shrews), Talpidae (true moles, shrew moles, and desmans), and Solenodontidae (solenodons).
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2015 SVP poster available upon request. Contact me.
Paper is in review in the Journal of Vertebrate Paleontology.
Paper is in review in the Journal of Vertebrate Paleontology.
