Loron and 14 co-authors reported in late January 2026 that Prototaxites was the first giant organism to live on the terrestrial surface, represented by columnar fossils of up to eight meters from the Early Devonian. However, its systematic affinity has been debated for over 165 years.
P. taiti material from the Rhynie chert.
See above inserts (A to C) for images of two of the four thin sections containing the fragments that constitute the P. taiti type material, including the fragment with medullary spots (B) and peripheral region (C). (D to L) P. taiti material used in this study. (D and E) Lyon 156 with P. taiti highlighted in dashed lines. (E) Thin section produced from the block in (D) showing the fractured P. taiti specimen. (F) Magnified image of the thin section in (E) showing the characteristic tubes and medullary spots of P. taiti. (G and H) Thin section made from Lyon 48 with P. taiti in dashed box. (H) Detail of thin section in (G) showing the tubes. (I to M) Imaging and reconstruction of a large, exceptionally well-preserved P. taiti from NSC.36. (I) Photogrammetry model of NSC.36 before cutting with surface exposed P. taiti circled by dashed line. (J) Photogrammetry model of NSC.36 after initial cutting of the block with P. taiti circled by a dashed line. (K) Block of NSC.36 from which thin sections were produced, showing medullary spots throughout the body. (L) Thin section taken from the block in (K) showing characteristic tubes and medullary spots of P. taiti. (M) Artist reconstruction of P. taiti within the Rhynie ecosystem including hypothesized reconstruction of the aerial portion.
Above illustrations by M. Humpage, Northern Rogue Studios. Scale bars: 3 m (M), 3 cm (I), 2 cm (J), 1 cm (D), 5 mm (E, G, and K), 1 mm (C), 500 μm (A and L), 200 μm (B and F), and 100 μm (H). Specimen accession codes: GLAHM Kid 2523 (A and B), GLAHM Kid 2525 (C), Lyon 156 (D), Lyon 156 MPEG0078 (E and F), NSC.36 (I to K), and NMS G.2024.5.7 (L).
There are now two remaining viable hypotheses: Prototaxites was either a fungus, or a member of an entirely extinct lineage. The authors investigated the affinity of Prototaxites by contrasting its organization and molecular composition with that of Fungi. They conclude that fossils of Prototaxites taiti from the 407-million-year-old Rhynie chert were chemically distinct from contemporaneous Fungi and structurally distinct from all known Fungi. This finding casts doubt upon the fungal affinity of Prototaxites, instead suggesting that this enigmatic organism is best assigned to an entirely extinct eukaryotic lineage.
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