A tapeworm in a dog is called the same thing, a tapeworm. The most common kind of tapeworm found in dogs is the Dipylidium Caninum, which is the cucumber tapeworm or double-pore tapeworm.
Well, tapeworms are in the phylum Platyhelminthes and the class Cestoda, but those wouldn't be their scientific names. Tapeworms are a large category of invertebrates, so you would have to know the species of tapeworm to found out its binomial nomenclature (Genus species).
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Platyhelminthes
tapeworm
the scientific name for tapeworm is 'Cestoda' .
notchus isus gayus
a tapeworm can get to 30 ft or more you can go see one at the Natural History Museum.
Cestodes, is another name for a tapeworm.
The tapeworm is in the animilia kingdom 
a tapeworm is a parasite, BAD!
The tapeworm is in kingdom Animalia