BIOL 321 Lecture Notes - Lecture 3: Lophophore, Limnognathia, Entoprocta
Document Summary
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 microscopicgastrotricha. 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, thegnathostomulida, micrognathozoa, and possibly the cycliophora these groups share the presence of complex jaws, from which they are called the gnathifera. The lophotrochozoa include two of the most successful animal phyla, the molluscaand annelida. The former, which is the second-largest animal phylum by number of described species, includes animals such as snails, clams, and squids, and the latter comprises the segmented worms, such as earthworms and leeches.
