Excavata
| Excavates Temporal range: | |
|---|---|
| Giardia lamblia, a parasitic diplomonad | |
| Scientific classification (obsolete as paraphyletic) | |
| Domain: | Eukaryota |
| (unranked): | Excavata (Cavalier-Smith), 2002 |
| Phyla and classes | |
|
See text | |
| Cladistically included but traditionally excluded taxa | |
Excavata is an obsolete, extensive and diverse paraphyletic group of unicellular Eukaryota. The group was first suggested by Simpson and Patterson in 1999 and the name latinized and assigned a rank by Thomas Cavalier-Smith in 2002. It contains a variety of free-living and symbiotic protists, and includes some important parasites of humans such as Giardia and Trichomonas. Excavates were formerly considered to be included in the now- obsolete Protista kingdom. They were distinguished from other lineages based on electron-microscopic information about how the cells are arranged (they have a distinctive ultrastructural identity). They are considered to be a basal flagellate lineage.
On the basis of phylogenomic analyses, the group was shown to contain three widely separated eukaryote groups, the discobids, metamonads, and malawimonads. A current view of the composition of the excavates is given below, indicating that the group is paraphyletic. Except for some Euglenozoa, all are non-photosynthetic.