A systematic review of the genus Tyzzeria Allen, 1936 (Chromista: Apicomplexa), including the molecular phylogenetic position of Tyzzeria parvula (Kotlán, 1933) Klimeš, 1963.

Tyzzeria Allen, 1936 is a coccidian genus traditionally associated with Anseriformes, although there are descriptions of Tyzzeria spp. from junglefowls, snakes, skinks and mice. In this sense, the current study performs a taxonomic review of Tyzzeria spp., evaluating those that should be valid, invalid or that require further studies for validation. Along with this review, oocysts morphologically identified as Tyzzeria parvula (Kotlán, 1933) Klimeš, 1963 were recovered from fecal samples of swan geese Anser cygnoid (Linnaeus, 1758) in the mountainous region of the State of Rio de Janeiro, which were molecularly identified through the sequencing of a locus of the small subunit ribosomal RNA (18S) gene, providing the first deposit of the genus Tyzzeria in GenBank. Finally, this sequence of T. parvula prompted a broad phylogenetic analysis covering species of the main chromist taxa, which evidenced homoplasies associated with taxonomic characters of gametogony, basic oocyst configuration and excystation structures; in addition to positioning T. parvula in a monophyletic group within the order Eimeriida together with Schellackia spp., Eimeria spp. and Caryospora-like spp. from reptiles and amphibians.