The complete sequence of the 18S small subunit (SSU) ribosomal DNA of Hammondia hammondi and Sarcocystis mucosa
was obtained and compared to SSU rDNA sequences of Neospora caninum, Toxoplasma gondii, Besnoitia besnoiti, 2 species
of Frenkelia, 3 species of Isospora, and 13 species of Sarcocystis. Analyses showed that H. hammondi and T. gondii are
monophyletic and that these taxa shared a common ancestor with N. caninum and B. besnoiti. The weight of evidence
shows that S. mucosa, S. neurona, and Frenkelia species form a clade thereby supporting the conclusion that Sarcocystis
is paraphyletic.