File:EssentialStructuresOfBasalAlveolates.gif

English: Essential structures (morphotype) of Colpodella, Perkinsus, and Parvilucifera (possibly basal alveolates). Complex anterior microtubular array from which the flagella emerge. Instead of only a posterior flagellar/feeding groove, we see both posterior and lateral grooves. At least one flagellum bears mastigonemes. The internal, alveolar membrane system is present, with micropores associated with the alveoli. Extrusomes (another apparent synapomorphy of Metabiotiformes) are present and take the form of elongate, somewhat club-shaped sacs terminating anteriorly. These are quite similar to the rhoptries of the Apicomplexa. Similarly, all genera have some sort of anterior conoid-like structure associated with predation or intracellular insertion in the Apicomplexa. Figure from Siddall et al. (2001).