The Platyzoa include the phylum Platyhelminthes, the flatworms. These were originally considered some of the most primitive Bilateria, but it now appears they developed from more complex ancestors. A number of parasites are included in this group, such as the flukes and tapeworms. Flatworms are acoelomates, lacking a body cavity, as are their closest relatives, the microscopic Gastrotricha. The other platyzoan phyla are mostly microscopic and pseudocoelomate. The most prominent are the Rotifera or rotifers, which are common in aqueous environments. They also include the Acanthocephala or spiny-headed worms, the Gnathostomulida, Micrognathozoa, and possibly the Cycliophora. These groups share the presence of complex jaws, from which they are called the Gnathifera. COUNT 5
QSN1 What is another name for flatworm? ANS1 Platyhelminthes QSN2 What are some parasites included in the Platyhelminthes group? ANS2 flukes and tapeworms QSN3 What does acoelomates mean? ANS3 lacking a body cavity QSN4 What are the flatworms closest relative? ANS4 Gastrotricha QSN5 Where are the rotifera most prominent? ANS5 in aqueous environments