Trichomonas vaginalis is a
Trichomonas vaginalis causative agent of trichomoniasis is classified as parabasalid based on presence of parabasal apparatus: Golgi complex linked to striated parabasal fibers, hydrogenosomes instead of mitochondria, four anterior flagella plus recurrent flagellum supporting undulating membrane, and lack of cyst stage. It inhabits human urogenital tract, replicates via longitudinal binary fission and transmission through sexual contact. Diplomonads have two nuclei, ciliates show nuclear dimorphism, apicomplexans possess apical complex. These ultrastructural criteria clearly place T. vaginalis
Ref: NCERT Class 11 Biology, Chapter 2: Protista; Campbell 12th ed., Chapter 28 Parabasalids; CDC Parasitology - Trichomonas