Origin of Life: early land life not long after the Cambrian (Introduction)

by David Turell , Monday, April 30, 2018, 19:18 (2400 days ago) @ David Turell

432 million years ago a land plant fossil:

https://www.newscientist.com/article/2167645-a-fossil-may-rewrite-the-story-of-how-plan...

"A plant fossil that gathered dust in a museum drawer for a century is the oldest fossil of large plants ever found.

"The find suggests we need to rethink the plant family tree. It has been estimated that land plants first emerged 515 million years ago but actual fossils are rare and not quite so old. Many botanists assume that the first land plants grew like mosses, and more complex plants like shrubs and trees evolved later.

"However, the new find adds to growing evidence that this picture may be back-to-front. Mosses and their relatives might be more “evolved” than we thought.

***

"Many botanists suspect that the moss condition evolved first, partly because mosses and their ilk seem to be the simplest living land plants. But a team led by Jiří Kvaček at the National Museum Prague, Czech Republic and Viktor Žárský at the Charles University, Prague says that this idea might be wrong – and they have fossil evidence.

"They have reanalysed a 432-million-year-old plant fossil that was discovered more than a century ago near Prague. The fossil belongs to a new species called Cooksonia barrandei. It is 4-5 centimetres high and up to 3 millimetres across.
“[The] Cooksonia barrandei we describe is the oldest unambiguous plant macrofossil known to date,“ says Žárský. The older fossils are all tiny fragments, mostly spores.

***

"Beyond its age, the fossil is significant because it is a sporophyte. Since it is big, it’s likely that C. barrandei’s sporophytes could sustain themselves using photosynthesis. That makes this ancient plant more like a modern tree or shrub than a moss.

"What’s more, since C. barrandei is one of the earliest well-preserved land plants we’ve found, the researchers say it’s possible that the common ancestor of land plants also had these self-sustaining sporophytes.

“'Until now it was assumed that the ‘higher plants’ evolved from [mosses and their relatives],” says Žárský. But mosses, with their reduced sporophytes, might actually have evolved later.

"It all comes down to reproduction.

“'I was genuinely surprised to see this fossil – it’s very cool,” says Kevin Boyce at Stanford University in California. He agrees C. barrandei may well have made sporophytes that could nourish themselves.

"However, Boyce says it’s unclear what the first land plants were like. “It’s now basically up in the air,” he says, partly because the fossil record of plants is so patchy. He is reluctant to draw conclusions from C. barrandei because some of its more recent relatives are believed to have had a moss-like life cycle.

"However, Paul Kenrick at the Natural History Museum in London, UK is open to the idea that the first land plants were not moss-like.

"Kenrich co-authored a study published in March that used molecular data to infer the lifestyle of the first land plants. The research suggested mosses and their relatives belong to a distinct group descended from a more complex ancestor.

“'This implies that [moss-like plants] and their life cycle may not be ancestral, but rather derived,” he says. “Life cycle evolution in the earliest emergent plants needs a rethink.'”

Comment: This is not long after the Cambrian Explosion of animals. It lead to the plant bloom that confused Darwin. Evolution always results in complexity.