Domain Eukaryota
Excavata

The Excavata super-kingdom contains a variety of single-celled, flagellated eukaryotes. Most are free-living but some symbiotic or parasitic.

The main characteristic uniting the Excavata is the flagellated feeding groove. The feeding groove is a complex construction of fibers and microtubules. They use this to capture and eat food particles suspended in liquid. They pull the food into the groove with a water current generated by beating flagella at the back of the groove.

Excavata have two, four or more flagella. They can have discoid mitochondria, tubular mitochondria, or no mitochondria at all. Some lack the feeding groove.

Their variety in form has long presented problems in classifying the Excavata. But considerable genetic study continues to clarify and confirm their close relationships.

Once thought to be 'primitive eukaryotes' because they often lack certain organelles, we now know they many 'discarded' or modified them after long adaptation.

----------------------------------------------------------------------------------------------------Excavata: Uncertain Classification - Malawimonas

The Malawimonas have one studied marine species. They have a feeding groove with two flagella; the front one beats actively, the rear with a 'vane'. They move by 'skidding' along surfaces and have mitochondria. Genetic studies place them between the Fornicata and the Parabasalia kingdoms.