Yuyuanozoon magnificissimi is the largest known vetulicolian, with the holotype (and only known specimen) measuring about 202 millimeters in length. In life, it would have been an egg-shaped animal with a long cylindrical tail. The body is divided into 6 segments, with a gill opening (that has gill filaments extending out from each opening) placed symmetrically on each side of every body segment starting at the second segment. The cylindrical tail is divided into 7 segments, and differs from the tails of all other known vetulicolians (not being flattened like vetulicolids like Vetulicola, and not oar-like or leaf-like like those of the didazoonids like Didazoon, and is unlike the tails of banffozoans like Banffia and Skeemella).