Excavata

Euglenozoa and Heterolobosea (Percolozoa) or Eozoa (Cavalier-Smith) appear to be particularly close relatives, and are united by the presence of discoid cristae within the mitochondria (Superphylum Discicristata). A close relationship has been shown between Discicristata and Jakobida,[15] the latter having tubular cristae like most other protists, and hence were united under the taxon name Discoba, which was proposed for this apparently monophyletic group.[2]

Metamonads are unusual in having lost classical mitochondria—instead they have hydrogenosomes, mitosomes or uncharacterised organelles. The oxymonad Monocercomonoides is reported to have completely lost homologous organelles.

The malawimonads have been proposed to be members of Excavata owing to their typical excavate morphology, and phylogenetic affinity to other excavate groups in some molecular phylogenies. However, their position among eukaryotes remains elusive.[3]

Ancyromonads are small free-living cells with a narrow longitudinal groove down one side of the cell. The ancyromonad groove is not used for "suspension feeding", unlike in "typical excavates" (e.g. malawimonads, jakobids, Trimastix, Carpediemonas, Kiperferlia, etc). Ancyromonads instead capture prokaryotes attached to surfaces. The phylogenetic placement of ancyromonads is poorly understood (in 2020), however some phylogenetic analyses place them as close relatives of malawimonads.[16]

This proposed cladogram for the positioning of the Excavata, with the Eukaryote root in the excavates, mainly follows Cavalier-Smith.[17][18][19][20][21][22][23][24][25]

This perspective treats the Excavata as polyphyletic, and some, including Cavalier Smith, argue that it should be abandoned.[26] In an alternative view, the Discoba have been suggested as sister to the rest of the Diphoda, once again breaking up the Excavata.[18][27]