Question

Balanoglossus is a member of which of animals?

Answer 1

Hint: It's an ocean-dwelling acorn worm (Enteropneusta) variety of extraordinary zoological interests in light of the fact that being a Hemichordate, it's an "evolutionary link" among invertebrates and vertebrates. It has a notochord within the upper part of the body and has no nerve chord. It does have a stomochord, however, which is a gut chord within the collar. Their heads could also be as small as 2.5 mm (1/10 in) or as large as 5 mm (1/5 in)

Complete answer
Balanoglossus belongs to the phylum Hemichordata, The animals in this group are also called acorn worms. They differ from chordates by not having a post-anal tail and notochord. Balanoglossus has a length of 1.5 meters. These have modified proboscis. These organisms have a threefold division of the body, with the preoral lobe, collar, and trunk. Trunk bears' digestive system. Balanoglossus is considered an "evolutionary link" between invertebrates and vertebrates.

Additional information
Balanoglossus is a burrowing and exclusively marine animal. It is present in shallow waters between tide marks along the coast of warm and calm seas. Balanoglossus is world-wide in distribution. Balanoglossus is tubicolous living in U-shaped burrows excavated within the sandy bottom. The walls of the tube are lined with mucus secreted by the mucous gland of the animal.
The burrows are open at both ends, and spiral coils of faeces like the castings of earthworms may be seen at the posterior opening. In its burrow, Balanoglossus lies during a twisted condition but its anterior and posterior extremities are straight. Knight Jones (1952) reported that the animal moves in its burrow with the assistance of cilia present everywhere the body.

Note: The body of Balanoglossus is soft, elongated, cylindrical, being richly ciliated all over and covered with mucus. The length of the animal varies from 2 cm to 2.5 meters. Most forms are drab-colored, though reddish tints are present, several species are luminescent due to mucus. They have an offensive odour. The body is bilaterally even and isolated into three districts, viz., proboscis or protostome, collar or mesosome, and trunk or metasome.