Boyce, C. KevinHotton, Carol L.Fogel, Marilyn L.Cody, George D.Hazen, Robert M.Knoll, AndrewHueber, Francis M.2009-09-112007Boyce, C. Kevin, Carol L. Hotton, Marilyn L. Fogel, George D. Cody, Robert M. Hazen, Andrew H. Knoll, and Francis M. Hueber. 2007. Devonian landscape heterogeneity recorded by a giant fungus. Geology 35(5): 399-402.0091-7613http://nrs.harvard.edu/urn-3:HUL.InstRepos:3293011The enigmatic Paleozoic fossil Prototaxites Dawson 1859 consists of tree-like trunks as long as 8 m constructed of interwoven tubes <50 mm in diameter. Prototaxites specimens from five localities differ from contemporaneous vascular plants by exhibiting a carbon isotopic range, within and between localities, of as much as 13%0 delta C-13. Pyrolysis-gas chromatography-mass spectrometry highlights compositional differences between Prototaxites and co-occurring plant fossils and supports interpretation of isotopic distinctions as biological rather than diagenetic in origin. Such a large isotopic range is difficult to reconcile with an autotrophic metabolism, suggesting instead that, consistent with anatomy-based interpretation as a fungus, Prototaxites was a heterotroph that lived on isotopically heterogeneous substrates. Light isotopic values of Prototaxites approximate those of vascular plants from the same localities; in contrast, heavy extremes seen in the Lower Devonian appear to reflect consumption of primary producers with carbon-concentrating mechanisms, such as cryptobiotic soil crusts, or possibly bryophytes. Prototaxites biogeochemistry thus suggests that a biologically heterogeneous mosaic of primary producers characterized land surfaces well into the vascular plant era.en-USpaleoecologypaleobotanyPaleozoicisotope geochemistryterrestrial ecosystemsPrototaxitesJournal Article10.1130/G23384A.1