An Analysis of Sediment Collected by Pogonomyrmex salinus from the Jurassic Sundance Formation, Bighorn Basin, Wyoming

Pogonomyrmex salinus is a species of harvester ant found in the Bighorn Basin area of Wyoming. Harvester ants are aptly named as they “harvest” seeds for food, but this harvesting behavior is also seen in their collection of sediment particles to build their mounds. For decades, paleontologists have looked to harvester ants for microfossils because the small size of the fossils makes them difficult for human eyes to find. But there are unresolved questions about the data that can be gleaned from the fossils collected by the ants. The mounds collected for this study include material from the Stockade Beaver Shale Member of the Sundance Formation, which dates to the Middle Jurassic Epoch. In this study, harvester ant mounds were collected and examined under microscope and the mounds sorted into their different components. The mounds were sorted into fossil materials, organic materials, and matrix. The fossil material was further sorted into taxa while the organic materials and matrix were loosely grouped according to likeness. For example, seed pods of any kind were grouped together and scat was grouped together. Through this process of sorting, questions of the ants’ collection preferences are explored. Questions include whether the ants exhibit a preference for fossils or non-fossiliferous materials. Further, of the fossils found , is there a specific fossil that they collect more than others, and is that reflective of the abundance of those taxa found from traditional collection methods? This study is novel because previous studies have not included the non-fossil material in the collection analysis. By including non-fossil material, the ants’ gathering biases can be more accurately identified, which will help to more accurately analyze data and glean a more full understanding of the paleo-community make up