According to Ramayana told by Valmiki, when Ahiravana took Rama and Lakshmana to Patala, Hanuman followed them to their rescue.
He was challenged at the gate of Patala by a creature, who was part Vanara and part reptile - a Makara. He introduced himself Makaradhwaja and son of Hanuman, the mighty warrior.
Hanuman was amused and said that, I am myself the Hanumana but he could not be his son, as he was born celibate. However, Hanumana then closed his eyes in dhyan to see the events described above of Makardhwaja's birth.
