Recently while researching on tradition of Sankhya from some articles and research papers , I have concluded that possible Guru-Shihya parampara would be Kapila > Asuri > Panchashikha > Varsaganya > Vindhyavasina > Ishwar Krishna. Though we also have one post on Guru Pampara of Ishvara Krishna.
After reading about every person of Guru Parampara, I found that probably Sankhya used not to be in textual form in the time of Kapil and Asuri or we don't have any text attributed to Kapila or Asuri surviving today. But the character Panchashikha is very interesting. His name is mentioned with great respect in Samkhya traditions (in various Sankhya commentaries). He is also mentioned in Mahabharata and Purana as a great teacher of Sankkhya. Panchashikha is said to had written a work called Shashti Tantra (षष्ठी तंत्र) which means sixty topics of Sankhya. This work was a great contribution to Sankhya. It probably reconstructed the atheistic sounding Sankhya of Kapila to theistic form. Ishwara Krishna also admits that his teaching of Sankhya is based on Shashthi Tantra.
सप्तत्यां किल येऽर्थास्तेऽर्था: कृत्स्नस्य षष्टितन्त्रस्य ।
आख्यायिकाविरहिता: परवादविवर्जिताश्चापि ॥ ७२ ॥
72. The subjects which are treated by the 70 distinches are the very subjects which are treated in Shashti Tantra also, (sixty topics) excluding the illustrative tales and omitting doctrines of other people.
So, it can be said that probably Shashti Tantra was the first textual form of Sankhya philosophy.
As we know that Sankhya Karika is the only oldest surviving work on Sankhya today we have, yet I want to know do we have any part or fractions of Shashti Tantra surviving? probably in the various commentaries on Sankhya texts?