Dear Ali,

I guess you mean the Glaucophyta. The relationships among the red algae, green algae, and glaucophytes, unfortunately are unclear. However, the glaucophytes are hypothesized to be similar to the original algal type that led to green plants and red algae, i.e. they may be a basal group. Of course they have Chl a but lack Chl b, that is typical of green algae and land plants. With reference to pigments, another important feature of glaucophytes is that, along with red algae and cyanobacteria, they possess phycocyanins (but not phycoerythrin). Another special feature of glaucophytes is that their plastid has a peptidoglycan layer, believed to be a relic of the endosymbiotic origin of plastids from cyanobacteria.

Best regards.

Marco

Dear Ali,

Marco Cantonati highlighted key differences between the Glaucophyta and green algae. If you want to know more details on the subject, I recommend the review by Dana C Price and colleagues in the Handbook of the Protists (see https://link.springer.com/content/pdf/10.1007%2F978-3-319-28149-0_42.pdf)

There is also this nice paper:

Article The Glaucophyta: The blue-green plants in a nutshell