Makardhwaja
Makardhwaja / Magardhwaja as per Hindu Mythology, is son of Hanuman, who makes his appearance in epic Valmiki Ramayana.
Birth
When Hanuman took a dip in the waters of sea, after burning whole of Lanka with the fire burning on his tail, a drop of his perspiration fell in to mouth of a mighty fish. Out of this the Makardhwaja was born.
According to another, slightly different version, when Hanuman took a dip in sea, for cooling himself after burning Lanka; a drop of his seed got discharged, due to extreme heat generated in his body and labor by him, which fell in to mouth of a giant fish-cum-reptile like creature, whose name was Makardhwaja, thus making it pregnant.
The fish was caught by people of Ahiravana, who ruled Patala, the nether-world. The Markardhwaja, was discovered, when stomach of fish was cut open and named after it. Ahiravana, seeing his strength & virility gave him job of guarding, the gates of his Kingdom.
Iconography
Makardhwaja name is derived from Hindu mythological creature Makara and depicted as part Makarā and part Vanarā (monkey).