Why did Sri Krishna say he is Usanas among seers?

Question

Sri Krishna says that he was Ushanas among seers in B.G.

वृष्णीनां वासुदेवोऽस्मि पाण्डवानां धनंजयः।

मुनीनामप्यहं व्यासः कवीनामुशना कविः।।10.37।।

Of the Vrsnis (the members of the Vrsni clan), I am the son of Vasudeva; of the sons of Pandu, Dhananjaya (Arjuna) [I am]; of the sages too, I am Vyasa; of the seers, the seer Usanas.

Sri Krishna also says he is Bhrigu among Maharshis.

महर्षीणां भृगुरहं गिरामस्म्येकमक्षरम्।

यज्ञानां जपयज्ञोऽस्मि स्थावराणां हिमालयः।।10.25।।

Of the great rishis, I am Bhrgu; of the words, I am the Single-syllable (Om); of the sacrifices [performed with external objects], I am the sacrifice of muttering prayer; of the immovables, I am the Himalayan range.

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Edit 15-7-19

I found the following mantra from Rig Veda, which mentions Usana.(IX.87.3)

Rsi and Sage, the Champion of the people, cleft and sagacious, Usana in wisdom, He hath discovered even their hidden nature, the Cows' concealed and most mysterious title.

Edit 22-7-2019

It was not Sri Krishna alone, who was greatest Yogi of his time, but even in Rig Veda, Indra stated that he was Usana.

अहम मनुर अभवं सूर्यश चाहं कक्षीवां रषिर अस्मि विप्रः |

अहं कुत्सम आर्जुनेयं नय ॠञ्जे ऽहं कविर उशना पश्यता मा ||

I was aforetime Manu, I was Sūrya: I am the sage Kakṣīvān, holy singer. Kutsa the son of Ārjuni I master. I am the sapient Uśanā behold me.

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Now my question is what is the greatness of Ushanas?

Answer 1

What does कविः mean and what is the greatness of Ushanas?

As per, Hindi Commentary By Swami Chinmayananda and Swami Ramsukhdas on BG10.37:

उशना (Usanas) is another name of Shukracharya. कविः is not just the author of a poetry but the one who is well-versed in scriptural principles; knower of the past, present and future.

Because Shukracharya is well-versed of the Sanjivani vidhya, author of Shukraniti and famous in Vedas, the God mentioned him as his Vibhuti.

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For what reason did Usanas obtain the name of Sukra?

Yudhishthira said, ... for what reason did Usanas obtain the name of Sukra?

Bhishma said, ... Kuvera, represented the matter unto Siva of immeasurable energy, that first of gods, fierce and amiable, and possessed of various forms. And he said, 'Usanas, having spiritualised himself by Yoga entered my form and depriving myself of liberty, has taken away all my wealth. Having by Yoga entered my body he has again left it.' Hearing these words, Maheswara of supreme Yoga-powers became filled with rage.

... The lord of Uma, beholding Bhargava thus brought upon the palm of his hand, opened his mouth. The chief of the gods then threw Bhargava into his mouth and swallowed him at once. The puissant and high-souled Usanas of Bhrigu's race, entering the stomach of Maheswara, began to wander there.'

...The great ascetic Usanas, however, O chastiser of foes, from within Mahadeva's stomach, repeatedly addressed the god, saying, 'Show me thy kindness!' Unto him Mahadeva said, 'Go out through my urethra.' He had stopped up all other outlets of his body. Confined on every side and unable to find out the outlet indicated, the ascetic began to wander hither and thither, burning all the while with Mahadeva's energy. At last he found the outlet and issued through it. In consequence of this fact he came to be called by the name of Sukra... ~Mahabharata: Santi Parva: Mokshadharma Parva: Chapter 289 [too keep it sort i have used ... to omit some text]

As mentioned above, he came to be known as Sukra (the word शुक्र is used for semen in Sanskrit/Hindi) because he came out from urethra (from where semen comes out). This is more clearly explained in Mahabharata in Sanskrit-Hindi by Pandit Ramnarayan Gita Press.

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What is the difference between कविः and महर्षि?

The definition of कविः is elaborated above. For ऋषि or महर्षि, see the rishi tag and already discussed posts here and here.

Answer 2

The greatness of Ushanas is due to Kavi. Hence Kavya Usanas, Usanas of Kavi, or from Kavi. Ushanas is the most famous of the Kavis. The original Kavis were a sub-line of Bhrgus.

Bhrgus home is in Bharuch, and also in that district is a town called Kavi, to remember the association of Kavis with Bhrgu.

Kavi became the most famous Kings of Iran, the Kayanian Dynasty.

Bhrgu, Kavi and Angiras are mentioned in Mahabharat as the most important names in history.

"When the seed of Brahman was thus poured as a libation on that sacrificial fire, there sprang from it, O mighty one, three beings into existence. They were three male persons, endued with bodies that partook of the characters of the circumstances from which they respectively sprang. One arose first from the flames of the fire (called Bhrig) and hence he came to be called by the name of Bhrigu. A second came from the burning charcoals (called Angara) and hence he came to be called by the name of Angiras. The third sprang from a heap of extinguished charcoals and he came to be called by the name of Kavi.

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Endued with every prosperity, Angiras came to be called the offspring of Agni, and the celebrated Kavi came to be known as the child of Brahman himself. Bhrigu and Angiras who had sprung from the flame and the charcoals of Agni respectively, became the procreators of extensive races and tribes in the world. Verily, these three, viz., Bhrigu and Angiras and Kavi, regarded as Prajapati, are the progenitors of many races and tribes. All are the children of these three."

https://en.krishnakosh.org/krishna/Mahabharata_Anushasna_Parva_Chapter_85:7 (8,9)

Kavi Usan, the Iranian Kavi Usanas, is also known in Arabic history, by Tabari associated with Soloman.

The Bhrgu, Kavi and Angiras names relate Indo-Aryan with wider Eurasian history, as those tribes are well-knwn in the West. Angiras can be identified with name Anglo.