ABSTRACT
The taxon Amphistomida comprises a natural group of digenetic trematodes which has the rank of order in the modern classification of higher taxa of trematodes. Morphologically, its generalized in-group feature is the posteroterminally spaced ventral sucker. The specific diagnosis of amphistomes requires the realization of more and more character states or, ideally, the full scope of these which are manifested by adult specimens. These character complexes may be gross morphological, histomorphological, and cytogenetic. The majority of amphistomes are characterized as having strongly developed body musculature and by the presence of a muscular apparatus around the oral opening, muscular elements around the genital pore, and a muscular ventral sucker. The muscular apparatus situated around the oral opening is a pharynx, including two morphologically clearly defined parts: the body of the pharynx itself and the appendages which are known in certain groups of amphistomes.
