It was multicellular, not unicellular, a predicted. From Nature News:
A mysterious deep-ocean seaweed diverged from the rest of the green-plant family around 540 million years ago, developing a large body with a complex structure independently from all other sea or land plants. All of the seaweed’s close relatives are unicellular plankton.
The finding, published today in Scientific Reports, upends conventional wisdom about the early evolution of the plant kingdom. “People have always assumed that within the green-plant lineage, all the early branches were unicellular,” says Frederik Leliaert, an evolutionary biologist at Ghent University in Belgium. “It is quite surprising that among those, a macroscopic seaweed pops up.”
“We still need to do a lot more sampling of those lineages,” says Delwiche. “I think the tree of life will become a lot more shrubby.” More.
Shrubby? That’s one way of describing it. Classic stasis is another.
Here’s the abstract:
The green plants (Viridiplantae) are an ancient group of eukaryotes comprising two main clades: the Chlorophyta, which includes a wide diversity of green algae, and the Streptophyta, which consists of freshwater green algae and the land plants. The early-diverging lineages of the Viridiplantae comprise unicellular algae, and multicellularity has evolved independently in the two clades. Recent molecular data have revealed an unrecognized early-diverging lineage of green plants, the Palmophyllales, with a unique form of multicellularity, and typically found in deep water. The phylogenetic position of this enigmatic group, however, remained uncertain. Here we elucidate the evolutionary affinity of the Palmophyllales using chloroplast genomic, and nuclear rDNA data. Phylogenetic analyses firmly place the palmophyllalean Verdigellas peltata along with species of Prasinococcales (prasinophyte clade VI) in the deepest-branching clade of the Chlorophyta. The small, compact and intronless chloroplast genome (cpDNA) of V. peltata shows striking similarities in gene content and organization with the cpDNAs of Prasinococcales and the streptophyte Mesostigma viride, indicating that cpDNA architecture has been extremely well conserved in these deep-branching lineages of green plants. The phylogenetic distinctness of the Palmophyllales-Prasinococcales clade, characterized by unique ultrastructural features, warrants recognition of a new class of green plants, Palmophyllophyceae class. nov. (public access) – Frederik Leliaert, Ana Tronholm, Claude Lemieux, Monique Turmel, Michael S. DePriest, Debashish Bhattacharya, Kenneth G. Karol, Suzanne Fredericq, Frederick W. Zechman, Juan M. Lopez-Bautista. Chloroplast phylogenomic analyses reveal the deepest-branching lineage of the Chlorophyta, Palmophyllophyceae class. nov.. Scientific Reports, 2016; 6: 25367 DOI: 10.1038/srep25367
See also: Tree of life morphs into … leaf?
Kirk Durston on the new Tree of Life
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