The phylum Platyhelminthes comprises about 20,000 species. They are commonly known as flatworms and include free-living aquatic flatworms (class Turbellaria), as well as the mostly parasitic flukes and tapeworms (classes Monogenea, Trematoda, and Cestoda). Collectively, they are primitive organisms that are flat, soft-bodied, and symmetrical. Recent molecular studies suggest that the Platyhelminthes as a whole may have arisen as two independent groups from different ancestral groups. If this is correct, most of the flatworms may belong to the Lophotrochozoa, a large group within the animal kingdom that includes molluscs and earthworms, while the rest are much more primitive.
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Flatworm: Procotyla fluviatilis
Photographs and information on these organisms.
Flatworms: British Marine Life Study Society
One page about a planarian and one page about the life cycle of the digenean Cryptocotyle lingua, with a few photographs.
Fredrick the Flatworm
Introduction to the Platyhelminthes
Introduction to the Platyhelminthes, the flatworms: life in two dimensions. One page of text with a few photographs.
Information on the minute intestinal fluke, Metagonimus yokogawai, which can parasitize the human gut, and a diagram and information on its life cycle.
An introduction to the phylum with more pages about the Turbellaria, Monogenea, Digenea and Cestoda, from Animal Diversity Web.
Platyhelminthes: Flatworms, Tapeworms, Flukes
Much information on the flatworms and the characteristics that distinguish them from other worm-like creatures, with photographs and diagrams.
Information on the digenetic blood trematodes of the genus Schistosoma which can infect humans, and a diagram and information on their complex life cycle.
Last update:January 5, 2016 at 12:05:08 UTC