Which can be excluded due to the absence of fossil records?

The body of a jellyfish can be excluded due to the absence of fossil records. Jellyfish are made primarily of soft, gelatinous tissue that does not typically fossilize well. In contrast, the shells of snails and crabs are made of harder materials that can be preserved in the fossil record, and the backbone of dinosaurs, being composed of bone, also has a good chance of being fossilized.