For 10 points, identify these lancelets noted for having myomeres, notochords, and all the other distinctive characteristics of chordates.
Pikaia and Yunnanozoon are two of the oldest known fossils of them. Food is digested in the iliocolonic ring and is enzymatically broken down in their hepatic cecum. The mouth of these organisms consists of a wheel organ that draws in water which is filtered by cirri on the oral hood. Like tunicates, water passes through a body cavity consisting of metapleural folds called the atrium and out the atriopore of organisms in this subphylum. Food particles are trapped in mucus by pharyngeal slits. These organisms are noted for their v-shaped musculature and flexible, body-length rod structure. For 10 points, identify these lancelets noted for having myomeres, notochords, and all the other distinctive characteristics of chordates.
Pikaia and Yunnanozoon are two of the oldest known fossils of them.
{Cephalochordata} [accept {Amphioxus} or {Branchiostoma}; prompt on “{lancelets}” before mentioned”]