SAR or Harosa is a highly diverse clade of eukaryotes, often considered a supergroup,[2] that includes stramenopiles (heterokonts), alveolates, and rhizarians.

[7] This groups excludes haptophytes and cryptomonads, hypothesized to have acquired plastids in separate endosymbiosis events,[13] leading Okamoto et al. (2009) to propose the clade Hacrobia to accommodate them.

[14] The SAR supergroup encompasses a variety of morphologies and ecological niches, from microscopic zoo- and phytoplankton to massive kelp forests.

On the other hand, Stramenopiles is well-defined morphologically, characterized by an anterior flagellum with tripartite bristles (mastigonemes), while Alveolata is united by the presence of cortical alveoli.

[17] Nonetheless, studies of telonemids, believed to be the sister group to SAR, have revealed characteristics such as tripartite hair and peripheral vacuoles, potentially homologous to similar structures in stramenopiles and alveolates.