Bangiomorpha pubescens

node · earth · Somerset Island, Nunavut

A fossil red alga from the Hunting Formation of Somerset Island in Arctic Canada, described by Nicholas Butterfield in 2000, and one of the most information-dense single fossils in the Precambrian record. It is important for three separate reasons at once. It is the oldest fossil that can be assigned to a living eukaryotic group with confidence, being closely comparable to the modern red alga Bangia. It shows differentiated cell types — a specialised holdfast anchoring the filament to the substrate — which is complex multicellularity rather than a chain of identical cells. And its reproductive structures indicate differentiated spores, taken as the oldest direct evidence of sexual reproduction in the fossil record. Originally dated to roughly 1.2 billion years, the host formation was redated in 2018 to about 1.05 billion years; the redating is worth noticing because it moved a calibration point used by molecular clocks and therefore shifted a series of downstream divergence estimates that were not themselves re-examined.