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First known feeding trace of the eocene bottom-dwelling fish Notogoneus osculus and its paleontological significance.

Martin AJ, Vazquez-Prokopec GM, Page M - PLoS ONE (2010)

Bottom Line: Nonetheless, trace fossils attributed to fish interacting with the lake bottom are apparently rare, and have not been associated directly with any fish species.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.Lastly, our spatial and mathematical analyses significantly update and advance previous approaches to the study of teleost trace fossils.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Studies, Emory University, Atlanta, Georgia, United States of America. geoam@learnlink.emory.edu

ABSTRACT

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.

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Trace fossil specimen FOBU-12718.A - Digital composite photograph of specimen. B – Digitally enhanced composite photograph, emphasizing contrast of trace fossil from host lithology. C – Digitized points assigned to waveforms in the trace fossil, with labeling tentatively assigned to presumed body parts (caudal fin, anal fin, pelvic fins, mouth). D – Fitted waveforms based on Fourier transform, showing extrapolated paths of body parts, and superimposed onto plots taken from trace fossil. Colors of fitted waveforms describe each presumed body part, as indicated in the legend.
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pone-0010420-g002: Trace fossil specimen FOBU-12718.A - Digital composite photograph of specimen. B – Digitally enhanced composite photograph, emphasizing contrast of trace fossil from host lithology. C – Digitized points assigned to waveforms in the trace fossil, with labeling tentatively assigned to presumed body parts (caudal fin, anal fin, pelvic fins, mouth). D – Fitted waveforms based on Fourier transform, showing extrapolated paths of body parts, and superimposed onto plots taken from trace fossil. Colors of fitted waveforms describe each presumed body part, as indicated in the legend.

Mentions: The trace fossil contains several interrelated waveforms (Figure 2A and Text S1). Among these are thin (<2 mm wide), shallowly impressed (<1 mm depth), paired, parallel, and synchronous grooves, separated by 5.2–5.5 cm and forming discontinuous sine-like waveforms of relatively low amplitude (3–4 cm) and long wavelength (27–28 cm). Three complete and two partial wavelengths of these coupled traces are preserved along the length of the slab. These trails are cross-cut by a single discontinuous waveform with a higher amplitude (9–10 cm), although its 27–28 cm wavelength is identical to those of the paired waveforms. This single waveform consists of four complete cycles and two partial ones. Another single but short (10 cm long), discontinuous segment of another waveform is slightly offset (2.8 cm maximum distance) from the high-amplitude one; its amplitude is less than that of the high-amplitude waveform. Medial to the paired and parallel waveforms are discontinuous markings consisting of incomplete, overlapping ellipsoids, about 1–2 cm wide, which join and bifurcate in places. (Please refer to Figure 2 and Text S1 for a detailed view of these waveforms.) The trend of these traces, however, is not strictly medial, and is occasionally proximal to either of the paired trails along the length of the trace fossil. Where these traces approach one side, the opposite-side parallel waveform is thinner or not recorded, resulting in consistent and predictable gaps in each waveform.


First known feeding trace of the eocene bottom-dwelling fish Notogoneus osculus and its paleontological significance.

Martin AJ, Vazquez-Prokopec GM, Page M - PLoS ONE (2010)

Trace fossil specimen FOBU-12718.A - Digital composite photograph of specimen. B – Digitally enhanced composite photograph, emphasizing contrast of trace fossil from host lithology. C – Digitized points assigned to waveforms in the trace fossil, with labeling tentatively assigned to presumed body parts (caudal fin, anal fin, pelvic fins, mouth). D – Fitted waveforms based on Fourier transform, showing extrapolated paths of body parts, and superimposed onto plots taken from trace fossil. Colors of fitted waveforms describe each presumed body part, as indicated in the legend.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2864752&req=5

pone-0010420-g002: Trace fossil specimen FOBU-12718.A - Digital composite photograph of specimen. B – Digitally enhanced composite photograph, emphasizing contrast of trace fossil from host lithology. C – Digitized points assigned to waveforms in the trace fossil, with labeling tentatively assigned to presumed body parts (caudal fin, anal fin, pelvic fins, mouth). D – Fitted waveforms based on Fourier transform, showing extrapolated paths of body parts, and superimposed onto plots taken from trace fossil. Colors of fitted waveforms describe each presumed body part, as indicated in the legend.
Mentions: The trace fossil contains several interrelated waveforms (Figure 2A and Text S1). Among these are thin (<2 mm wide), shallowly impressed (<1 mm depth), paired, parallel, and synchronous grooves, separated by 5.2–5.5 cm and forming discontinuous sine-like waveforms of relatively low amplitude (3–4 cm) and long wavelength (27–28 cm). Three complete and two partial wavelengths of these coupled traces are preserved along the length of the slab. These trails are cross-cut by a single discontinuous waveform with a higher amplitude (9–10 cm), although its 27–28 cm wavelength is identical to those of the paired waveforms. This single waveform consists of four complete cycles and two partial ones. Another single but short (10 cm long), discontinuous segment of another waveform is slightly offset (2.8 cm maximum distance) from the high-amplitude one; its amplitude is less than that of the high-amplitude waveform. Medial to the paired and parallel waveforms are discontinuous markings consisting of incomplete, overlapping ellipsoids, about 1–2 cm wide, which join and bifurcate in places. (Please refer to Figure 2 and Text S1 for a detailed view of these waveforms.) The trend of these traces, however, is not strictly medial, and is occasionally proximal to either of the paired trails along the length of the trace fossil. Where these traces approach one side, the opposite-side parallel waveform is thinner or not recorded, resulting in consistent and predictable gaps in each waveform.

Bottom Line: Nonetheless, trace fossils attributed to fish interacting with the lake bottom are apparently rare, and have not been associated directly with any fish species.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.Lastly, our spatial and mathematical analyses significantly update and advance previous approaches to the study of teleost trace fossils.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Studies, Emory University, Atlanta, Georgia, United States of America. geoam@learnlink.emory.edu

ABSTRACT

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.

Show MeSH