Giant magnetofossils

Giant magnetofossils are microscopic (1 - 4 µm) magnetic minerals, typically a product of the biomineralization of magnetite (Fe₃O₄).^{[1] [2]} They are associated with the umbrella of magnetofossils coinciding with conventional magnetofossils (20-200nm) which are ancestral remains of bacterial organisms (magnetotactic bacteria). The organisms associated with giant magnetofossils are hypothesized to be microbial but largely unknown because they have no modern or fossil analogs. Giant magnetofossils are found in marine sediments spanning from the Cretaceous (97 Ma) to the modern geologic record in the Cenozoic.^{[3] [4]} Though they may occur in a wide range of various aquatic environments globally.^[5] They are particularly well-studied surrounding global climactic events i.e. the Paleocene-Eocene Thermal Maximum (~56 Ma).

There are 4 widely accepted morphologies of giant magnetofossils (bullets, spindles, needles, and spearheads). Largely their purpose is poorly understood outside of the preliminary hypothesis of their necessity is the organisms’ navigational capabilities, protective armor, structural integrity, magnetic properties, or hardness which are all shape and size dependent. Their distinct morphology and chemical signature indicate that they must be of biogenic origin which is undisputed; however, the organism responsible for their creation and purpose is unknown.