The type family Sphaeropleaceae differs from many other sphaeroplealeans in ITS2 secondary structure (Keller et al. 2008), although most lineages discussed in the present study have not been tested in that way. It is possible that Sphaeropleaceae are sister to the remaining (“crown”) Sphaeropleales as suggested by previous studies Z VAD FMK (e.g., Wolf et al. 2002, Tippery et al. 2012). The order Sphaeropleales is characterized by a putatively strong ultrastructural synapomorphy, the directly opposed (DO) basal flagellar bodies in motile cells, and even though swimming

cells of the Sphaeropleaceae differ ultrastructurally from the remainder of the order, they retain the basic DO organization. The Sphaeropleaceae contain the filamentous Sphaeroplea, and the solitary Ankyra and Atractomorpha. These algae are coenocytic, contain pyrenoids with traversing cytoplasm, and reproduce via zoospores or sexually via anisogamy or oogamy. Motile cells have been described in detail by Hoffman (1984) and Cáceres et al. (1997). In addition, Tsarenko (2005) lists four families

as members of the Sphaeropleales that were not included in our study: Characiaceae, Chlorosarcinaceae, Gloeotilaceae, and Microsporaceae. Characiaceae, as discussed above, is a problematic taxon because the higher taxonomic affiliation of the lectotype species (Characium sieboldii A. Braun) remains unclear. Nevertheless, the classification proposed in this study H 89 is not affected by this uncertainty. The family Chlorosarcinaceae was not considered

in this study because it had been demonstrated by Deason and Floyd (1987) that Chlorosarcina Atezolizumab chemical structure has a counter-clockwise arrangement of flagellar basal bodies, which rules it out as a member of Chlorophyceae. Similarly, even though the type of the genus has not been verified phylogenetically, Gloeotila was shown to group with trebouxiophytes in Verghese (2007). Likewise, no type material of Microspora is available for phylogenetic examination, and therefore the family was not considered in the present study. Interestingly, unpublished data by Buchheim and Buchheim (http://www.bio.utulsa.edu/deepestgreen/Geminella.htm) weakly suggest that one Microspora-like strain (UTEX LB472) may be a relative of Sphaeropleales. However, Durako (2007) showed the same strain as a relative of Chaetophorales. The phylogenetic position of Microsporaceae will require further investigation, and likely additional field collections to designate a type specimen/culture for the generitype of Microspora, M. abbreviata (Rabenhorst) Lagerheim. Rotundella rotunda gen. et sp. nov. Fučíková, P. O. Lewis & L. A. Lewis (Fig. 1, a–f) Cells spherical to ovoid or irregular (5–) 8–20 μm in diameter. In young cells, chloroplast single, cup-shaped or lobed, and parietal; at maturity, chloroplasts multiple but large and few in numbers, parietal.