John J. Jacisin III: Vertebrate Paleontology, Herpetology, Geology


Hello, and welcome to my website!  I am currently a PhD candidate performing research in the Lawing Lab directed by Dr. Michelle Lawing, at Texas A&M University's Department of Ecosystem Science and Management. Feel Free to explore my website to learn about my research, or take a look at my CV!

My research implements a highly interdisciplinary approach to understanding the effects of environmental change on natural systems and organisms from local to global scales in the past, present, and future. I wield tools in sedimentology, stratigraphy, paleontology, statistics, ecology, biology, field methods, and climatology to develop new methods for modeling and understanding how biotic systems and environments evolve, interact, and affect each other through time. My main contributions are the development and application of ecometrics, as well as the investigation of Cenozoic-to-present environmental change, future environmental projections, and the evolution, biogeography, and morphology of Cenozoic reptiles and amphibians.

How do biotic systems spatially and temporally interact with environmental change?

Through their traits, organisms interface with their environments on all temporal and geographic scales. Ecomorphological traits can be developed into ecometrics when measured across a group of species in a community. Ecometrics is the geographic study of functional trait distributions at the community level and their relationships to environmental and climatic factors, and can be applied to a variety of organisms, including mammals, reptiles, birds, and plants. My current research on this topic uses geometric morphometrics to identify five aspects of shape change in North American snake vertebrae that are related to ecology, then uses those relationships to develop an ecometric, vertebral shape, by modeling the average shape for snake communities across a 50km grid of the United States and Canada. Regressions and maximum likelihood models suggest that snake community morphology can be used as an ecometric indicator of vegetation cover, Bailey’s ecoregion province, and temperature, and have potential as proxies for paleoenvironmental interpretation. Future directions for this research include spatially expanding the dataset, investigating the role of regional to continental geologic history such as tectonics on model predictions, applying ecometrics to North American fossil communities containing extant taxa to reconstruct paleoenvironments, using maximum likelihood predictions to predict changes in functional trait distributions given projected future changes in climate, and testing the predictive limits of ecometrics on novel ecosystems or communities containing only extinct taxa.

Evolution, gaps, and biases in the Cenozoic record of fossil reptiles and amphibians.

Biases pertaining to preservation, collection, and identification, which in turn causes problems for understanding the evolution of reptiles and amphibians and the environments in which they occur. While little can be done about preservation bias, the other two biases can be addressed. To address collection biases, I employ microfossil collection techniques such as sediment screening and anthill collecting in fossiliferous localities. This has led to a profound increase in available fossil material for understudied herpetofaunas, most recently in collaborative fieldwork with the University of New Mexico investigating the Eocene-Oligocene Climate Transition. I also search in collections for localities that have been extensively collected, but in which herpetofaunas have not been described. This has resulted in new information regarding the pattern of diversification, modernization, and climatic relationships during the major radiation of snakes in North America, including the first record of a fossil snake assemblage immediately following the North American Mid-Miocene Climatic Optimum.

I also work to address identification biases in the fossil record, something that fossil reptiles and amphibians have historically suffered from because of perceived stability, similar morphologies, lack of specimens, and other such complications. This has resulted in the over-splitting of some taxa, where variation is not adequately considered, and over-grouping of other taxa, where everything similar in appearance is identified as the same thing based on biogeography or lack of large-scale analyses. I have worked to address such issues in fossil salamanders through comparative phylogenetic analysis and the description of new specimens, such as in my paper on North American fossil newts; this resulted in the realization that North American fossil newt species have more detailed descriptions of skeletal morphology than most extant North American newt species, resulting in poor phylogenetic resolution at the species level. I have also focused on apomorphic descriptions of fossil snakes to identify what aspects make one species unique when compared to others morphologically. In the future, I plan to apply morphometric and quantitative methods to identify unbiased methods of identification and interpretation to explore how well snakes can be identified and ecologically classified through isolated skeletal elements.

Fieldwork and Other Research

My fieldwork is primarily paleontological, stratigraphic, and sedimentary in nature, but also occasionally uses GIS and Remote Sensing data for scouting purposes. I have experience as both a field assistant and as a primary researcher in places such as Wyoming, Oregon, New Mexico, Utah, and Nebraska, primarily from the Cretaceous to the Pleistocene. Presently, my active field research is located in Eocene- to Oligocene-aged beds in Nebraska, and I have plans to expand both geographically and temporally in the future to better understand the biostratigraphy and sedimentological processes throughout the environmental changes of the Cenozoic.
I am presently in the early stages of collaborative research with groups working on fossil faunas in the La Brea Tar Pits of California and Natural Trap Cave in Wyoming as a fossil herpetofauna specialist. I am also implementing a test of the ability of morphometrics to predict ecologies from individual vertebrae in snakes. I am working on methods for delimiting fossil and extant species through vertebral and skull morphology. Finally, I intend to contribute to conservation paleobiology and conservation efforts by developing paleophylogeographic species distribution models, which combine fossil, geologic, climatic, and phylogenetic data to improve the predictive power of species distribution models by adding a deep time perspective to observed biogeographic patterns.

Areas of Special Interest: vertebrate paleontology, paleoecology, herpetology, conservation paleobiology, sedimentary geology geometric morphometrics, ecometrics, morphology, evolution, phylogenetics.