Solution:
Development in Petromyzon is indirect and includes a larval stage called ammocoete. Petromyzon is marine but migrates for spawning to fresh water. After spawning, within a few days, they die. Their larvae, after metamorphosis, return to the ocean.
Pristis (Chondricthyes), Pteropus (Mammalia), Psittacula (Aves) exhibit direct development. They do not undergo metamorphosis.
