The Mesomycetozoea (or DRIP clade, or Ichthyosporea) are a small group of Opisthokonta in Eukaryota (formerly protists), mostly parasites of fish and other animals. Significance They are not particularly distinctive morphologically, appearing in host tissues as enlarged spheres or ovals containing spores, and most were originally classified in various groups as fungi, protozoa, or colorless algae. However, they form a coherent group on molecular trees, closely related to both animals and fungi and so of interest to biologists studying their origins. In a 2008 study they emerge robustly as the sibling-group of the clade Filozoa, which includes the animals. Huldtgren et al., following x-ray tomography of microfossils of the Ediacaran Doushantuo Formation, has interpreted them as mesomycetozoan spore capsules. Terminology The name DRIP is an acronym for the first protozoa identified as members of the group, Cavalier-Smith later treated them as the class Ichthyosporea, since they were all parasites of fish. order Dermocystida "D": Dermocystidium. One species, Rhinosporidium seeberi, infects birds and mammals, including humans. "R": the "rosette agent", now known as Sphaerothecum destruens order Ichthyophonida "I": Ichthyophonus "P": Psorospermium Since other new members have been added (e.g. the former fungal orders Eccrinales and Amoebidiales), Mendoza et al. suggested changing the name to Mesomycetozoea, which refers to their evolutionary position. On Eukaryota tree, in Opisthokont clade, Mesomycetozoea is in the middle ("Meso-") of the fungi ("-myceto-") and the animals ("-zoea"). Note the name Mesomycetozoa (without a third e) is also used to refer to this group, but Mendoza et al. use it as an alternate name for basal Opisthokonts. Phylogeny Taxonomy Class Ichthyosporea Cavalier-Smith 1998 Order Dermocystida Cavalier-Smith 1998 Family Rhinosporidiaceae Mendoza et al. 2001 Genus Amphibiocystidium Pascolini et al. 2003 Genus Chromosphaera Grau-Bové et al. 2017 Genus Dermocystidium Pérez 1908 [Amphibiothecum Feldman, Wimsatt & Green, 2005; Dermocystis Pérez 1907 non] Genus Dermosporidium Carini 1940 Genus Dermotheca Genus Rhinosporidium Minchin & Fantham 1905 Genus Sphaerothecum Arkush et al. 2003 (Rosette agent) Genus Valentines Borteiro et al. 2018 Order Ichthyophonida Cavalier-Smith 1998 [Ichthyophonae Mendoza et al. 2001; Amoebidiales; Eccrinales Léger & Dubosq 1929] Suborder Sphaeroformina Cavalier-Smith 2012 Family Creolimacidae Cavalier-Smith 2012 Genus Anurofeca Baker, Beebee & Ragan 1999 Genus Creolimax Marschall et al. 2008 Genus Sphaeroforma Jostensen et al. 2002 [Pseudoperkinsus Figueras et al. 2000] Family Psorospermidae Cavalier-Smith 2012 Genus Psorospermis Cavalier-Smith 2012 [Psorospermium Hilgendorf 1883 non Eimer 1870] Family Piridae Cavalier-Smith 2012 Genus Caullerya Chatton 1907 Genus Abeoforma Marshall &