While studying a marine animal, a biologist observes that a solid, rod-like supporting structure is present exclusively in the tail region of its larval stage and completely disappears in the adult form. Identify the subphylum to which this animal belongs, along with a correct representative example.

Step-by-step solution

In the subphylum Urochordata (also known as Tunicata), the notochord is present only in the larval tail and is lost during retrogressive metamorphosis into the adult form. Ascidia, Salpa, and Doliolum are examples of Urochordata given in NCERT. Cephalochordates (e.g., Branchiostoma) retain the notochord from head to tail throughout life. Vertebrates (e.g., Petromyzon) have the notochord replaced by a vertebral column. Hemichordates (e.g., Balanoglossus) possess a stomochord in the collar region, not a true notochor