'Oldest plants on Earth' discovered

[nitpicker]

http://www.bbc.com/news/science-environment-39267153

'Oldest plants on Earth' discovered

By Helen Briggs
BBC News

2 hours ago

From the section Science & Environment

The origins of plants may go back hundreds of millions of years earlier than previously thought, according to fossil evidence. Ancient rocks from India suggest plants resembling red algae lived 1.6 billion years ago in what was then shallow sea. The discovery may overturn ideas of when relatively advanced life evolved, say scientists in Sweden. They identified parts of chloroplasts, structures within plant cells involved in photosynthesis.
(snip)

Therese Sallstedt of the Swedish Museum of Natural History discovered some of the fossils. She described them as "the oldest fossil plants that we know of on Earth in the form of 1.6 billion year old red algae". "They show us that advanced life in the form of eukaryotes (like plants, fungi and us humans/animals) have a much deeper history on Earth than what we previously have thought," she told BBC News.

The scientists found thread-like fossils and more complex "fleshy" colonies in sedimentary rock from central India. Both have characteristics of modern red algae, a type of seaweed. Co-researcher Prof Stefan Bengtson of the Swedish Museum of Natural History added: "You cannot be 100% sure about material this ancient, as there is no DNA remaining, but the characters agree quite well with the morphology and structure of red algae."

The oldest known red algae before the present discovery date back 1.2 billion years. The Indian fossils are 400 million years older, suggesting that the early branches of the tree of life began much earlier than previously thought.
(snip)

[Botany]

1. The oldest blue green algae go back 3.5 billion years

http://www.ucmp.berkeley.edu/bacteria/bacteriafr.html

[TeacherB87]

2. No shade, but...

Red algae is a protist, not a plant. They are unicellular while plants are multicellular. Based on the article, it seems what they've discovered is not an ancient plant but a plant-like protist.

[muriel_volestrangler]

3. Red algae are typically multicellular

In the system of Adl et al. 2005, the red algae are classified in the Archaeplastida, along with the glaucophytes and green algae plus land plants (Viridiplantae or Chloroplastida). The authors use a hierarchical arrangement where the clade names do not signify rank; the class name Rhodophyceae is used for the red algae. No subdivisions are given; the authors say, "Traditional subgroups are artificial constructs, and no longer valid."[21]

Many studies published since Adl et al. 2005 have provided evidence that is in agreement for monophyly in the Archaeplastida (including red algae).[22][23][24][25] However, other studies have suggested Archaeplastida is paraphyletic.[26][27] As of January 2011, the situation appears unresolved.

Below are other published taxonomies of the red algae using molecular and traditional alpha taxonomic data; however, the taxonomy of the red algae is still in a state of flux (with classification above the level of order having received little scientific attention for most of the 20th century).[28]

If one defines the kingdom Plantae to mean the Archaeplastida, the red algae will be part of that kingdom
If Plantae are defined more narrowly, to be the Viridiplantae, then the red algae might be considered their own kingdom, or part of the kingdom Protista.

https://en.wikipedia.org/wiki/Red_algae