Sprecher
Beschreibung
Prototaxites was the first giant organism to inhabit the terrestrial surface, represented by columnar fossils reaching up to eight meters in height from the Early Devonian. Its peculiar anatomy has led to debate over its systematic affinity for more than 165 years. Currently, two main hypotheses exist: Prototaxites was either a fungus or a member of an entirely extinct lineage. Today, morphological observations can be complemented by molecular-scale analytical techniques, providing new data on fossil material and shedding light on longstanding palaeontological questions. Here, we demonstrate how supervised and unsupervised machine-learning approaches applied to Fourier Transform Infrared Spectroscopy (FTIR) data from iconic 407-million-year-old Rhynie Chert fossils, including new and historical specimens of Prototaxites taiti, can help resolve questions surrounding their uncertain biology. We contrasted the molecular composition of Prototaxites with that of fungi and other fossils preserved with it in the chert. Our results reveal that Prototaxites was chemically and anatomically distinct from contemporaneous fungi. Coupled with high-resolution morphological investigations using confocal laser microscopy, and biomarker analyses, these findings cast doubt on the fungal affinity of Prototaxites, instead suggesting that this enigmatic organism is best assigned to a distinct extinct eukaryotic lineage. Moreover, these results interrogate the biological nature of other nematophytes, like Nematoplexus.