Relationship to metazoans Félix Dujardin, a French biologist interested in protozoan evolution, recorded the morphological similarities of choanoflagellates and sponge
choanocytes and proposed the possibility of a close relationship as early as 1841. Genome sequencing shows that, among living organisms, the choanoflagellates are most closely related to animals. suggesting this was the
morphology of their last common ancestor. The last common ancestor of animals and choanoflagellates was unicellular, perhaps forming simple colonies; in contrast, the last common ancestor of all
eumetazoan animals was a multicellular organism, with differentiated tissues, a definite "body plan", and embryonic development (including gastrulation). }}
Phylogenetic relationships The choanoflagellates were included in
Chrysophyceae until Hibberd, 1975. Recent molecular
phylogenetic reconstruction of the internal relationships of choanoflagellates allows the polarization of character evolution within the clade. Large fragments of the nuclear
SSU and
LSU ribosomal RNA,
alpha tubulin, and
heat-shock protein 90 coding genes were used to resolve the internal relationships and character polarity within choanoflagellates. These divisions are now known to be
paraphyletic, with convergent evolution of these forms widespread. The third family of choanoflagellates, the Acanthoecidae, has been supported as a monophyletic group. This clade possess a
synapomorphy of the cells being found within a basket-like lorica, providing the alternative name of "Loricate Choanoflagellates". The Acanthoecid lorica is composed of a series of
siliceous costal strips arranged into a species-specific lorica pattern." The choanoflagellate tree based on molecular phylogenetics divides into three well supported
clades. Clade 1 and Clade 2 each consist of a combination of species traditionally attributed to the Codonosigidae and Salpingoecidae, while Clade 3 comprises species from the group taxonomically classified as Acanthoecidae. The mapping of character traits on to this phylogeny indicates that the
last common ancestor of choanoflagellates was a marine organism with a differentiated
life cycle with
sedentary and
motile stages. '' sp. section under
TEM Taxonomy Choanoflagellates; •
Order Craspedida Cavalier-Smith 1997 em. Nitsche et al. 2011 •
Family Salpingoecidae Kent 1880-1882 •
under PCM sp. under light microscopy, isolated from Siberian buried soils.
colony under PCM ?Dicraspedella'' Ellis 1930 • ?
Diploeca Ellis 1930 • ?
Diplosigopsis Francé 1897 • ?
Pachysoeca Ellis 1930 • ?
Piropsis Meunier 1910 • ?
Salpingorhiza Klug 1936 • ?
Sphaerodendron Zhukov, Mylnikov & Moiseev 1976 non Seemann 1865 • ?
Stelexomonas Lackey 1942 •
Astrosiga Kent 1880-1882 •
Aulomonas Lackey 1942 •
colony (approx. 230 individuals) under light microscopy.Choanoeca'' Ellis 1930 •
Cladospongia Iyengar & Ramathan 1940 •
Codonosigopsis Senn 1900 •
Diplosiga Frenzel 1891 •
Hartaetosiga Carr, Richter & Nitsche 2017 •
Mylnosiga Carr, Richter & Nitsche 2017 •
Lagenoeca Kent 1881 •
Microstomoeca Carr, Richter & Nitsche 2017 •
Paramonosiga Jeuck, Arndt & Nitsche 2014 •
Salpingoeca James-Clark 1868 non Ellis 1933 •
Stagondoeca Carr, Richter & Nitsche 2017 •
Family Codonosigaceae Kent 1880-1882 •
Codosiga James-Clark 1866 •
Desmarella Kent 1880-1882 •
Kentrosiga Schiller 1953 •
Monosiga Kent 1880-1882 •
Proterospongia Kent 1882 •
Sphaeroeca Lauterborn 1894 non Meyrick 1895 •
Stylochromonas Lackey 1940 •
Order Acanthoecida Norris 1965 em. Nitsche et al. 2011 (Loricate choanoflagellates) •
Conioeca Thomsen & Ostergaard 2019 •
Family Acanthoecidae Norris 1965 em. Nitsche et al. 2011 (Nudiform choanoflagellates) •
Acanthoeca Ellis 1930 •
Enibas Schiwitza, Arndt & Nitsche 2019 •
Helgoeca Leadbeater 2008 •
Polyoeca Kent 1880 •
Savillea Loeblich III 1967 •
Family Stephanoecidae Leadbeater 2011 (Tectiform choanoflagellates) • ?
Conion Thomsen 1982 • ?
Spiraloecion Marchant & Perrin 1986 •
Acanthocorbis Hara & Takahashi 1984 •
Amoenoscopa Hara & Takahashi 1987 •
Apheloecion Thomsen 1983 •
Bicosta Leadbeater 1978 •
Calliacantha Leadbeater 1978 •
Calotheca Thomsen & Moestrup 1983 non Desv. 1810 non Spreng. 1817 non Heyden 1887 •
Cosmoeca Thomsen 1984 •
Crinolina Thomsen 1976 non Smetana 1982 •
Crucispina Espeland & Throndsen 1986 •
Diaphanoeca Ellis 1930 •
Didymoeca Doweld 2003 •
Kakoeca Buck & Marchant 1991 •
Monocosta Thomsen 1979 non Monocostus Schumann 1904 •
Nannoeca Thomsen 1988 •
Parvicorbicula Deflandre 1960 •
Pleurasiga Schiller 1925 •
Polyfibula Manton 1981 •
Saepicula Leadbeater 1980 •
Saroeca Thomsen 1979 •
Spinoeca Thomsen, Ostergaard & Hansen 1995 non Poulsen 1973 •
Stephanacantha Thomsen 1983 •
Stephanoeca Ellis 1930 •
Syndetophyllum Thomsen & Moestrup 1983 •
Thomsenella Özdikmen 2009 ==Genomes and transcriptomes==