Alveolate
The alveolates ("with cavities") is one of the major groups of protists, considered a clade and a superphylum of Eukarya called Alveolata.
Phyla
Within Alveolata, there are around 9 major and minor phyla, which are very diverse in form, but are now known to be related on various ultrastructural and genetic similarities:
Apicomplexa – parasitic protozoa that lack axonemal locomotive structures except in gametes
Ciliates – very common protozoa with many short cilia arranged in rows, and two nuclei
Dinoflagellates – mostly marine flagellates many of which have chloroplasts
Chromerida – a marine phylum of photosynthetic protozoa
Perkinsozoa
Colpodella
Voromonas
Acavomonidia
Colponemidia
Acavomonidia and Colponemidia were previously grouped together as colponemids, a taxon now split based on ultrastructural analysis. Acavomonidia is closer to the dinoflagellate/perkinsid group than Colponemidia is.
Characteristics
The most notable shared characteristic is the presence of cortical alveoli, flattened vesicles packed into a continuous layer supporting the membrane, typically forming a flexible pellicle. In dinoflagellates they often form armor plates. Alveolates have mitochondria with tubular cristae and their flagella or cilia have a distinct structure.