pleuromastigaceae pleuromastigaceae pleuromastigaceae is an obsolete family of cryptomonads, which included genera monomastix, pleuromastix, and xanthodiscus. pleuromastigaceae scientific classification domain: eukaryota division: cryptophyta class: cryptophyceae order: cryptomonadales family: pleuromastigaceaebourrelly 1970 ex silva 1980 genera ?opisthostigma pleuromastix xanthodiscus today, monomastix is regarded as a green alga, and since 1987 xanthodiscus is regarded as a synonym of prorocentrum. pleuromastix remains unclassified as a part of any larger taxon as of 2019.