[16] Like many members of euglyphids it is covered by rows of siliceous scales, and use filose pseudopods to crawl over the substrate of the benthic zone.

[21] P. chromatophora was discovered in sediments of the river Rhine on Christmas Eve 1894 by German biologist Robert Lauterborn, who named it Paulinella after his stepmother Pauline.

[25] The endosymbiotic event happened about 90–140 million years ago when an α-cyanobacterium (rather than a β-cyanobacterium which the plastids in Archaeplastida originates from),[26] who diverged about 500 million years ago from the ancestors of its sister clade that consist of the living members of the cyanobacteria genera Prochlorococcus and Synechococcus,[27][28][5][16] was permanently established within the amoeba.

[34][35] Some of the genes the nucleus received from the chromatophore were multiplied many times over through a "copy-paste" mechanism called retrotransposition, enabling them to function more efficiently and making them more tolerant against toxic compounds associated with photosynthesis.

[42] The presence of extant heterotrophic lineages makes Paulinella a valuable model for unravelling early stages of primary endosymbiosis event and studying the post symbiotic genome evolution of both the plastid and the host.