Professional Affiliations and Activities


  • Member, The Paleontological Society (2011 - Present)
  • Member, Society of Systematic Biologists (2014 - Present)
  • Member, The Society of Vertebrate Paleontology (2012 - Present)
  • Member, Society for the Study of Evolution (2014 - Present)
  • Member, Geological Society of America (2011 - Present)

Education & Certifications


  • BS, Yale University, Geology and Geophysics: Paleontology and Geobiology (2014)

Current Research and Scholarly Interests


Scientists and non-scientists have forever marveled at the great degree to which life varies in size. Even within modern animals, body sizes span more than 10 orders of magnitude! Biological rules populate the scientific literature in attempts to explain how and why animal body sizes vary. However, very little research has dealt with the effect major environmental adaptations, such as living in water versus on land or living in salt water versus in fresh water, have on body size evolution. One case of a significant relationship can be seen in mammals and reptiles, where we know that marine groups are much larger than their terrestrial relatives.

My overall goal is to improve our understanding of the effect of major evolutionary environmental transitions on the sizes of organisms. Using phylogenetic comparative methods, I analyze various animal groups that inhabit an array of different habitats (such as marine, freshwater, and terrestrial environments) for significant differences in body size between group members that inhabit those different habitats. Taking into account fossil taxa and geologic time, I analyze the reaction of body sizes of these taxa to environmental transitions.

I also employ machine learning to compile data using the DeepDive software, which has been produced by Christopher Ré’s lab at Stanford. I am further developing this software to analyze images in the paleontological literature, producing measurements for specimens that would otherwise never have been included in body size datasets.

Currently, my research is focused on Gastropods (snails and slugs). Gastropoda, the largest group within molluscs, comprises more than 60,000 species of snails, slugs, and limpets, more than one quarter of which are extinct. Gastropod body size spans eight orders of magnitude, with the smallest gastropods having shell volumes of less than .03 cubic millimeters and the largest gastropods having shell volumes of nearly 14,000 cubic centimeters. They are cosmopolitan in distribution and occupy a wide range of habitats, ranging from high mountains to deserts and rainforests, coral reefs, lagoons, and the deep sea, and from the tropics to high latitudes. They are the only molluscs that can be found in deep sea and shallow sea marine, estuarine, freshwater, and terrestrial habitats. Gastropods have made the transition between marine and freshwater and between marine and terrestrial environments more than 4 independent times. While many different animal groups may inhabit both marine and non-marine habitats, this evolutionary history and the long time span over which it has taken place make gastropods uniquely suited for studying the relationships of body size and habitat over time.

Lab Affiliations


2018-19 Courses


All Publications


  • Energetic tradeoffs control the size distribution of aquatic mammals. Proceedings of the National Academy of Sciences of the United States of America Gearty, W., McClain, C. R., Payne, J. L. 2018; 115 (16): 4194–99

    Abstract

    Four extant lineages of mammals have invaded and diversified in the water: Sirenia, Cetacea, Pinnipedia, and Lutrinae. Most of these aquatic clades are larger bodied, on average, than their closest land-dwelling relatives, but the extent to which potential ecological, biomechanical, and physiological controls contributed to this pattern remains untested quantitatively. Here, we use previously published data on the body masses of 3,859 living and 2,999 fossil mammal species to examine the evolutionary trajectories of body size in aquatic mammals through both comparative phylogenetic analysis and examination of the fossil record. Both methods indicate that the evolution of an aquatic lifestyle is driving three of the four extant aquatic mammal clades toward a size attractor at ∼500 kg. The existence of this body size attractor and the relatively rapid selection toward, and limited deviation from, this attractor rule out most hypothesized drivers of size increase. These three independent body size increases and a shared aquatic optimum size are consistent with control by differences in the scaling of energetic intake and cost functions with body size between the terrestrial and aquatic realms. Under this energetic model, thermoregulatory costs constrain minimum size, whereas limitations on feeding efficiency constrain maximum size. The optimum size occurs at an intermediate value where thermoregulatory costs are low but feeding efficiency remains high. Rather than being released from size pressures, water-dwelling mammals are driven and confined to larger body sizes by the strict energetic demands of the aquatic medium.

    View details for PubMedID 29581289

  • Comparative anatomy of the bony labyrinth of extant and extinct porpoises (Cetacea: Phocoenidae) BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY Racicot, R. A., Gearty, W., Kohno, N., Flynn, J. J. 2016; 119 (4): 831-846

    View details for DOI 10.1111/bij.12857

    View details for Web of Science ID 000388505600006

  • Melanin Concentration Gradients in Modern and Fossil Feathers PLOS ONE Field, D. J., D'Alba, L., Vinther, J., Webb, S. M., Gearty, W., Shawkey, M. D. 2013; 8 (3)

    Abstract

    In birds and feathered non-avian dinosaurs, within-feather pigmentation patterns range from discrete spots and stripes to more subtle patterns, but the latter remain largely unstudied. A ∼55 million year old fossil contour feather with a dark distal tip grading into a lighter base was recovered from the Fur Formation in Denmark. SEM and synchrotron-based trace metal mapping confirmed that this gradient was caused by differential concentration of melanin. To assess the potential ecological and phylogenetic prevalence of this pattern, we evaluated 321 modern samples from 18 orders within Aves. We observed that the pattern was found most frequently in distantly related groups that share aquatic ecologies (e.g. waterfowl Anseriformes, penguins Sphenisciformes), suggesting a potential adaptive function with ancient origins.

    View details for DOI 10.1371/journal.pone.0059451

    View details for Web of Science ID 000317418500041

    View details for PubMedID 23555675

    View details for PubMedCentralID PMC3608712