Question

multiple choice question
what structure extends past the anus in all chordate embryos and is retained in many adult chordates?
postanal tail
cranium
pharyngeal pouch
spicule

Explanation:

Chordates have four key features: notochord, dorsal - hollow nerve cord, pharyngeal slits, and postanal tail. The postanal tail extends past the anus in chordate embryos. In many adult chordates (like fish, some mammals), it is retained. The cranium is part of the skull (in vertebrates which are a subgroup of chordates). Pharyngeal pouches are related to the pharyngeal slits (involved in feeding and respiration in some chordates but not the structure extending past the anus). Spicules are found in sponges (non - chordates).

Answer:

postanal tail