"The third and final supergroup to be considered in this section is the Excavata, which includes primitive eukaryotes and many parasites with limited metabolic abilities. These organisms have complex cell shapes and structures, often including a depression on the surface of the cell called an excavate. The group Excavata includes the subgroups Fornicata, Parabasalia, and Euglenozoa. The Fornicata lack mitochondria but have flagella. This group includes Giardia lamblia (also known as G. intestinalis or G. duodenalis), a widespread pathogen that causes diarrheal illness and can be spread through cysts from feces that contaminate water supplies."