A Revision of the Order Pellitida Smirnov et al., 2011 (Amoebozoa, Discosea) Based on Ultrastructural and Molecular Evidence, with Description of Endostelium crystalliferum n. sp.

We present the results of an ultrastructural re-investigation of two amoebae strains that can be identified morphologically as previously described species of the genus Pellita, as well as the first molecular phylogenetic analysis of these amoebae based on SSU rRNA and actin gene sequences. The results obtained show close relationships between the genera Pellita, Gocevia, and Endostelium. These relationships are further supported by the description of Endostelium crystalliferum n. sp., which shares morphological characters simultaneously with Pellita spp. and Endostelium zonatum. The three genera form a robust clade that branches deeply within Amoebozoa, among either Flabellinia, or Longamoebia, depending on taxon sampling. The results suggest that Gocevia and Endostelium should not be included in the Himatismenida; therefore, we transfer the family Goceviidae into Pellitida. The type of cell organisation that was considered to be typical of Himatismenida (a lens-shaped cell covered dorsally with a flexible layer of organic material) has most probably evolved in some of these amoebae independently of Cochliopodiidae and Parvamoebidae. The robustness of the Pellitida clade in the molecular trees is consistent with the fine structure cytoplasmic evidence for these taxa, in particular, the presence of a centrosphere (a dictyosome-associated lamellar MTOC) in all these genera.