Class Aconoidasida Conoid present only in the ookinete of some species Order Haemospororida Macrogamete and microgamete develop separately. Syzygy does not occur. Ookinete has a conoid. Sporozoites have three walls. Heteroxenous: alternates between vertebrate host (in which merogony occurs) and invertebrate host (in which sporogony occurs). Usually blood parasites, transmitted by blood-sucking insects. Order Piroplasmorida Class Conoidasida Subclass Gregarinasina Order Archigregarinorida Order Eugregarinorida Suborder Adeleorina Suborder Eimeriorina Order Neogregarinorida Subclass Coccidiasina Order Agamococcidiorida Order Eucoccidiorida Order Ixorheorida Order Protococcidiorida Class Perkinsasida Order Perkinsorida Family Perkinsidae The name Protospiromonadida has been proposed for the common ancestor of the Gregarinomorpha and Coccidiomorpha. Another group of organisms that belong in this taxon are the corallicolids. These are found in coral reef gastric cavities. Their relationship to the others in this phylum has yet to be established. Another genus has been identified - Nephromyces - which appears to be a sister taxon to the Heamatozoa. This genus is found in the renal sac of molgulid ascidian tunicates. Evolution All members of this phylum are parasitic and evolved from a free-living ancestor. This lifestyle is presumed to have evolved at the time of the divergence of dinoflagellates and apicomplexans. Further evolution of this phylum has been estimated to have occurred about . The oldest extant clade is thought to be the archigregarines. These phylogenetic relations have rarely been studied at the subclass level. The Haemosporidia are related to the gregarines, and the piroplasms and coccidians are sister groups. The Haemosporidia and the Piroplasma appear to be sister clades, and are more closely related to the coccidians than to the gregarines. Marosporida is a sister group to Coccidiomorphea. Janouškovec et al 2015 presents a somewhat different phylogeny, supporting the work of others showing multiple events of plastids losing photosynthesis. More importantly this work provides the first phylogenetic evidence that there have also been multiple events of plastids becoming genome-free. See also Centrocone References External links SAR supergroup phyla Endoparasites