What is the story of Vishnu's incarnation Jayanta, son of Yama?

Question

In this chapter of the Srimad Bhagavatam, various sons of Yama god of death are described:

The ten daughters given to Yamarāja were named Bhānu, Lambā, Kakud, Yāmi, Viśvā, Sādhyā, Marutvatī, Vasu, Muhūrtā and Saṅkalpā. Now hear the names of their sons. O King, a son named Deva-ṛṣabha was born from the womb of Bhānu, and from him came a son named Indrasena. From the womb of Lambā came a son named Vidyota, who generated all the clouds. From the womb of Kakud came the son named Saṅkaṭa, whose son was named Kīkaṭa. From Kīkaṭa came the demigods named Durgā. From Yāmi came the son named Svarga, whose son was named Nandi. The sons of Viśvā were the Viśvadevas, who had no progeny. From the womb of Sādhyā came the Sādhyas, who had a son named Arthasiddhi. The two sons who took birth from the womb of Marutvatī were Marutvān and Jayanta. Jayanta, who is an expansion of Lord Vāsudeva, is known as Upendra. The demigods named the Mauhūrtikas took birth from the womb of Muhūrtā. These demigods deliver the results of actions to the living entities of their respective times. The son of Saṅkalpā was known as Saṅkalpa, and from him lust was born. The sons of Vasu were known as the eight Vasus. Just hear their names from me: Droṇa, Prāṇa, Dhruva, Arka, Agni, Doṣa, Vāstu and Vibhāvasu.

My question is, what is the story of Vishnu's incarnation Jayanta, who is the son of Yama and Marutvati?

The only Jayanta I'm familiar with is Jayanta son of Indra, whose eye was poked out by Rama's Brahmastra as I discuss in this answer. And the other name he's known by, Upendra, is usually used to refer to Vishnu's incarnation Vamana the dwarf, because he was the younger brother of Indra.

In any case, are there any other scriptures which mention Yama's son Jayanta, and/or give his story?

Answer 1

There seems to be some mix up between Yama and Dharma which has been discussed in other questions as well. However coming to this specific one, Srimad Bhagvatam in Section 1.6.3 Birth of Daksh from Prachetas mentions the ten ladies you have named in your question as the wives of Dharma:

Shukdev says, "Parikshit the names of Dharma's ten wives were Bhanu, Lamba, Kakubhi, Jami, Vishwas, Sadhya, Marutvati, Vasu, Muhurta and Sankalpa.

The Brahma Puran also mentions a similar list with Marutvati as one of Dharma's wives:

The ten daughters who were married to the god Dharma were named Arundhati, Vasu, Yami, Lamba, Bhanu, Marutvati, Sankalpa, Muhurta, Sadhya and Vishva.

The Brahma-Vaivarta Puran gives the same list:

The Garud Puran also mentions the same:

However, there is another list in the Bhagvatam that gives them different names:

Shraddha, Maitri, Daya, Shanti, Tushti, Pushti, Kriya, Unnati, Buddhi, Medha, Titiksha, Hree and Murti are the wives of Dharma.

As regard the mention of Vishnu's incarnation, that is explained by the list of Dharma's progeny. Following the order observed in the list of Dharma's wives, their children are, Rita (truth), Prasáda (favour), Abhaya (fearlessness), Sukha, Muda (pleasure), Smaya (wonder), Yoga (devotion), Darpa, Artha (meaning), Smriti (memory), Kshema, Prasraya (affection), and the two saints Nara and Náráyańa, the sons of Dharma by Múrtti.

Both Nar and Narayan are mentioned as Lord Vishnu's incarnations in the Puraans which is also confirmed in Mahabharat:

In days of yore, O Partha, I was, for some reason, born as the son of Dharma, O chief of Kuru's race, and in consequence of such birth of mine I was celebrated under the name of Dharmaja. I took birth in two forms, viz., as Nara and Narayana.

Hence the sentence you have quoted in your question may actually be referring to this relationship and this Jayanta is most likely the name of Nara or Narayan born of Murti/Marutvati.

Answer 2

I think that this can only be explained in the basis of Rig Veda. In Rig Veda Indra is the chief god and Vishnu is his younger brother/crown prince/assistant. The story of Jayanta son of Indra might be a reference to this. Jayanta is the second of Indra thus he is Upendra. He is Vishnu of Vedas.