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Author Notes:

Correspondence: geoam@learnlink.emory.edu

Conceived and designed the experiments: AJM.

Performed the experiments: AJM.

Analyzed the data: AJM GMVP MCP.

Contributed reagents/materials/analysis tools: AJM GMVP MCP.

Wrote the paper: AJM GMVP MCP.

We are grateful to Arvid Aase (Fossil Butte National Monument), who invited one of us (AJM) to examine specimens of Undichna in the Fossil Butte National Monument collections, which led to the discovery of FOBU-12718 in their collections.

Arvid also digitally photographed the specimen and merged the images to make the full-sized photograph used for spatial analysis.

Warfield Fossils, Inc. is thanked for donating the specimen to Fossil Butte National Monument so that it could be studied.

We appreciate the U.S. National Park Service for providing camping equipment for the brief time AJM spent at Fossil Butte in July 2008.

Jenni Scott (University of Saskatchewan) is appreciated for discussions with AJM about the paleoecology of the Green River Formation in this region.

Ruth Schowalter, the wife of AJM, was a valued and supportive companion while he gathered the primary data for this study on location at Fossil Butte.

Emory University provided the proper computer hardware and software for the spatial and mathematical analyses of FOBU-12718.

Jacob Benner (Tufts University), Andrew Frake (editor, PLoS), and an anonymous reviewer provided many helpful suggestions for improving the manuscript, for which we are thankful.

Of course, any mistakes in the final version are very much our own, and we regret them in advance.

Finally, we acknowledge the generations of researchers who have studied the fossil fish of the Green River Formation since the late 19th century.

We are extremely humbled to know that Notogoneus osculus was first described by Edward Cope in 1885, yet only now are we learning more about how it lived in Fossil Lake.

The authors have declared that no competing interests exist.

The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.


Research Funding:

The only funding was internal travel money from the Department of Environmental Studies (Emory University) provided to AJM.

First Known Feeding Trace of the Eocene Bottom-Dwelling Fish Notogoneus osculus and Its Paleontological Significance


Journal Title:



Volume 5, Number 5


, Pages e10420-e10420

Type of Work:

Article | Final Publisher PDF


Background: The Green River Formation (early Eocene, about 42–53 Ma) at and near Fossil Butte National Monument in Wyoming, USA, is world famous for its exquisitely preserved freshwater teleost fish in the former Fossil Lake. Nonetheless, trace fossils attributed to fish interacting with the lake bottom are apparently rare, and have not been associated directly with any fish species. Here we interpret the first known feeding and swimming trace fossil of the teleost Notogoneus osculus Cope (Teleostei: Gonorynchidae), which is also represented as a body fossil in the same stratum. Methodology/Principal Findings: A standard description of the trace fossil, identified as Undichna cf. U. simplicatas, was augmented by high-resolution digital images and spatial and mathematical analyses, which allowed for detailed interpretations of the anatomy, swimming mode, feeding behavior, and body size of the tracemaker. Our analysis indicates that the tracemaker was about 45 cm long; used its caudal, anal, and pelvic fins (the posterior half of its body) to make the swimming traces; and used a ventrally oriented mouth to make overlapping feeding marks. We hypothesize that the tracemaker was an adult Notogoneus osculus. Conclusions/Significance: Our results are the first to link a specific teleost tracemaker with a trace fossil from the Green River Formation, while also interpreting the size and relative age of the tracemaker. The normal feeding and swimming behaviors indicated by the trace fossil indicate temporarily oxygenated benthic conditions in the deepest part of Fossil Lake, counter to most paleoecological interpretations of this deposit. Lastly, our spatial and mathematical analyses significantly update and advance previous approaches to the study of teleost trace fossils.

Copyright information:

© 2010 Martin et al.

This is an Open Access work distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
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