Cyclomedusa is a genus of animal from the Edicarian period. It is flat and disc-like in shape. Not much is known about this animal, as even scientists can't agree on what it is. It was once believed to have been an early jellyfish. However, it was later determined to be a benthic, bottom-dwelling creature. Some scientists have even proposed that it is a microbial colony.
In The Land Before Time
An imaginary, stylized Cyclomedusa in its original jellyfish form is briefly seen during the song Big Water in The Land Before Time V: The Mysterious Island. It is seen floating above the main characters.