Vamśānukramaṇikā: Varuṇa–Kali Descendants and the Naiṛta Grahas
Genealogical Catalogue
यन्मार्त्तण्डो भवेत्युक्तस्त्वण्डात्सोंडे द्विधाकृते / तस्माद्विवस्वान्मार्त्तण्डः पुराणज्ञैर्विभाव्यते
yanmārttaṇḍo bhavetyuktastvaṇḍātsoṃḍe dvidhākṛte / tasmādvivasvānmārttaṇḍaḥ purāṇajñairvibhāvyate
Because, when the egg was split in two, he was told, “Become Mārtaṇḍa,” therefore the knowers of the Purāṇas regard Vivasvān as Mārtaṇḍa.