Spongiophyton was a thallose fossil of the early to mid-Devonian, which is notoriously difficult to classify.

Spongiophyton displayed dichotomous branching, and a flattened/elliptical cross section with a thick (20–80 μm) upper cuticular surface.

[8] It has most recently been interpreted on morphological[9] and isotopic[10] grounds as a lichen—which would place it with Winfrenatia among the earliest known representatives of this group.

But in deducing this they relied solely on their own data, neglecting to include published datasets or bryophytes from a wide range of habitats.

They also failed to take into account any adjustment necessary to overcome post-burial alteration of the δ13C, or to compensate for the different isotopic composition of the early Devonian atmosphere.