Abstract
As fossilized feces, coprolites represent direct evidence of animal behavior captured in the fossil record. They encapsulate past ecological interactions between a consumer and its prey and, when they contain plant material, can also guide paleoenvironmental reconstructions. Here we describe the first coprolites from the lagerstätte Rancho La Brea (RLB) in Los Angeles, California, which also represent the first confirmed coprolites from an asphaltic (“tar pit”) context globally. Combining multiple lines of evidence, including radiocarbon dating, body size reconstructions, stable isotope analysis, scanning electron microscopy, and sediment analyses, we document hundreds of rodent coprolites found in association with plant material, and tentatively assign them to the woodrat genus Neotoma. Neotoma nests (i.e., middens) and their associated coprolites inform paleoclimatic reconstructions for the arid southwestern US but are not typically preserved in coastal areas due to environmental and physiological characteristics. The serendipitous activity of an asphalt seep preserved coprolites and their original cellulosic material for 50,000 years at RLB, yielding a snapshot of coastal California during Marine Isotope Stage 3. This discovery augments the proxies available at an already critical fossil locality and highlights the potential for more comprehensive paleoenvironmental analyses at other asphaltic localities globally.
Highlights
Coprolites are some of the most important ichnofossils that can be recovered from a diversity of taphonomic, ecological, and geologic contexts[1]
The intact digested matter present in Quaternary coprolites can provide crucial evidence for testing ecological questions that may be otherwise difficult to address in the fossil record and that can be examined with techniques suitable for bridging fossil and modern samples
We combine multiple lines of evidence to identify and describe the coprolites and their paleoecological significance, including radiocarbon dating, stable isotope analysis, scanning electron microscopy (SEM), and comparative measurements. Both body size reconstructions and a plant macrofossil context suggest that the coprolite producer was of the genus Neotoma, a group of rodents whose middens form the backbone of paleoclimatic inferences across arid and high elevation ecosystems of North America
Summary
Coprolites are some of the most important ichnofossils that can be recovered from a diversity of taphonomic, ecological, and geologic contexts[1]. We combine multiple lines of evidence to identify and describe the coprolites and their paleoecological significance, including radiocarbon dating, stable isotope analysis, scanning electron microscopy (SEM), and comparative measurements Both body size reconstructions and a plant macrofossil context suggest that the coprolite producer was of the genus Neotoma, a group of rodents whose middens form the backbone of paleoclimatic inferences across arid and high elevation ecosystems of North America. These specimens provide a direct window into the behavior of a still-extant small mammal and the base of a southern California food web ~50,000 years ago, during Marine Isotope Stage 3 prior to the last glacial maximum. As there are three other fossiliferous asphaltic localities in California alone (Carpinteria, McKittrick, and Maricopa18) and more than a dozen globally across the Americas and Eurasia[23], we suggest that closer inspection using quantitative analyses for identifying taphonomic diversity would help improve palaeoecological reconstructions based on these deposits
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