Flatworms
A phylum of invertebrates that comprises the flatworms. Example sentences. 1  Like other members of the phylum Platyhelminthes, those of the class Turbellaria are dorsoventrally compressed, with high surface area to volume ratios. Platyhelminthes. The phylum name Platyhelminthes literally means flatworms.. Members of this phylum are soft, thin-bodied, leaf or ribbonlike worms, including the familiar planaria of ponds and streams, as well as the flukes and tapeworms parasitic in human and other animal bodies. Scientists believe that the first turbellarians evolved around 550 MYA (million years ago). Platyhelminthes are mostly worm like creatures that are dorsoventrally flattened, meaning they look like a ribbon, this is why they are called names such as Tapeworm, Flatworm, Fluke and Planarian. The Platyhelminthes are a successful phylum with around 25,000 known species divided into four classes. Most Platyhelminthes are parasites on other animals, only the Turbellarians are mostly non-parasitic. A few species are commensalists living in harmony, or mutual benefit with another, normally larger organism. Definition of FLATWORM. : any of a phylum (Platyhelminthes) of soft-bodied usually much flattened acoelomate worms (as the planarians, flukes, and tapeworms) —called also platyhelminth. See flatworm defined for kids. ADVERTISEMENT.
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what does the phylum name platyhelminthes mean