Web document 18.2. The Phylum Bilateria.

 

The bilateria are bilaterally symmetric animals. The coelom is the body cavity of an animal. Acoelomata lack a body cavity. Coelomata have a body cavity that is lined with mesodermal tissue, while Pseudocoelomata such as the nematode C. elegans have a body cavity lined with other tissue.

 

TABLE 18-9Phylum Bilateria

Superphylum

Phylum

Species Example

Acoelomata

Platyhelminthes (flatworms)

Schistosoma mansoni

Coelomata

Deuterostomia (e.g. chordates, echinoderms, arrow worms)

Homo sapiens

 

Protostomia [e.g. mollusks, leeches, arthropods (insects)]

Drosophila melanogaster

Pseudocoelomata

Acanthocephala (thorny-headed worms)

Moniliformis moniliformis

 

Cycliophora

Symbion pandora

 

Gastrotricha

Draculiciteria tesselata

 

Kinorhyncha

Pycnophyes kielensis

 

Nematoda (roundworms)

Caenorhabditis elegans

 

Nematomorpha (horsehair worms)

Gordius aquaticus

 

Rotifera

Adineta vaga

Source: Adapted from the classification at NCBI (http://www.ncbi.nlm.nih.gov/Taxonomy/).