Fossil plant spores (charophyte algae) found in Western Australia, dating form the Ordovician period (480 mya), are thought to provide insight into plants venturing onto land:
“I think [the paper] is interesting for a few reasons,” says paleobiologist Philip Donoghue of the University of Bristol who was not involved with the study. “It extends the fossil record of [early land plants] by something like 20 million years. . . . Also, potentially [the fossils] provide a sort of intermediate between the Cambrian record and the later Ordovician records.”
Plants that live on land are thought to have evolved from algae—typically aquatic plants lacking stems, roots, leaves, and vascular systems. But when and how plants first adapted to life on land is a matter of debate. The first macrofossil evidence of land plants is in the form of 425 million-year-old specimens of Cooksonia, a primitive vascular plant. However, molecular clock estimates—which are based on, among other things, genetic mutation rates—have suggested an origin for land plants in the Cambrian period (approximately 505 million years ago).
This 80-million-year disconnect between the molecular and fossil data exists in part because molecular genetic changes always precede morphological ones, says Donoghue. Other researchers have suggested that it might also be because early land plants had soft, nonvascular tissues that would not have been well preserved.
Ruth Williams, “Discovered: Fossilized Spores Suggestive of Early Land Plants” at The Scientist, (August 12, 2021)
The big story here isn’t about the disconnect between molecular and fossil data; it’s about how early on more complex life forms got started (all that complexity in such a short time isn’t looking good for random mutations).
The paper is closed access.
You may also wish to read: Microbial fossils found at 3.4 billion years ago at the sub sea floor level. It’s not entirely clear that these were life forms but if they were, it’s further evidence that life got started pretty much when the planet cooled and not, apparently, as a result of some long, slow, Darwinian process.