The excavates are a major assemblage of unicellular eukaryotes, often known as Excavata. The phylogenetic category Excavata contains a variety of free-living and symbiotic forms, and includes some important parasites of humans. Characteristics Many excavates lack 'classical' mitochondria - these organisms are often referred to as 'amitochondriate', although, most, perhaps all, retain a mitochondrial organelle in greatly modified form. Others have mitochondria with tubular, discoidal, or in some… (More on Excavata)