Which Extant Chordates are Postulated to Be Most Like the Earliest

Question

Which extant chordates are postulated to be most like the earliest chordates in appearance?
A) lancelets
B) adult tunicates
C) amphibians
D) reptiles
E) chondrichthyans

Accepted Answer

Lancelets, also known as amphioxus, are thought to be the most basal extant chordates and are postulated to resemble the earliest chordates in appearance. They have a simple, elongated body with a notochord, dorsal nerve cord, and pharyngeal slits that are similar to those found in early fossil chordates. Adult tunicates, on the other hand, have a more derived morphology that is modified for their specialized filter-feeding lifestyle, while amphibians, reptiles, and chondrichthyans are all more derived vertebrates with characteristic adaptations such as limbs, scales, and jaws.