Question: Why do we ask about the conclusion about the Tachash? Rav Yosef's Beraisa taught that only skin of Tahor animals is Kosher for Meleches Shamayim!

Rashi: His Beraisa does not refer to the Mishkan (rather, to Tefilin).

Why is it called 'a species unto itself'?

Maharsha: This is unlike other cases where it says so. Rather, it is a Safek, like it says 'Chachamim did not determine if it is a Chayah or Behemah.' Tosfos said like this in Yevamos (83a) about Androginus (one with male and female genitals). It is a species unto itself; Chachamim did not determine if it is a male...

Did Tachash exist only at that time? It says "va'En'alech Tachash"!

Maharsha: This refers to Dor ha'Midbar, at that time (they made shoes from its skin).

Daf Al ha'Daf citing Taima d'Kra (Shemos 39:34): In "Oros ha'Eilim... Oros ha'Techashim", the first Oros is Malei with two Vov's, and the latter is Chaser, without any Vov. Tanchuma (Terumah 6) says that there was one giant Tachash, 30 Amos long; its skin sufficed to cover the Mishkan. We must say that there were others, from which they made covers from the Kelim. (NOTE: Even if we would say that it was only five Amos wide, so its front and back (top and bottom) together comprised the 10 Amos width to cover the Mishkan, perhaps skin on its legs was used to cover the Kelim! However, if "va'En'alech Tachash" applies to most or many of Dor ha'Midbar, one Tachash 30 Amos would not suffices to make shoes for them without a miracle. Would it not be more appropriate for "Techashim" to be written Chaser, to show that there was only one? Perhaps "Oros" is Chaser, to teach that it was one connected hide. They did not need to attach hides, e.g. from its back and front. - PF)

Iyun Yakov (30b): 'The Tachash in the days of Moshe' implies that other Tachashim, e.g. in Yechezkel, were a different species; perhaps they were Temei'im. So says Mizrachi (Parshas Terumah). Maharsha says that it was the same species; Tosfos (Yevamos 102b) implies like this.

Anaf Yosef: Do not say that Hash-m created it at the time - "Ein Kol Chadash Tachas ha'Shemesh"! We must say that they exist in Midbaros. Hash-m summonsed them for Moshe from those Midbaros. 'Nignaz' implies that it is in the world, like it says that Yoshiyah was Gonez the Aron, and it is in the world, like it says in Yoma. This is unlike Tanchuma (Terumah 6), which says that it was a miracle. It was created at the time, and Nignaz.

What do we learn from the ox that Adam offered?

Maharal: The Temei'im were created only for the sake of the Tehorim. Adam was the first person, therefore he was created one. The first ox had one horn, for it was one and the first of other animals. Surely Tehorim were before Temei'im! The ox resembled Adam, who was the middle of the creations, and was created from the Mizbe'ach, in the middle of the world, like I wrote in Gur Aryeh (Bereishis Perek 2). Taharah is in the middle; Tum'ah is to the sides. Also the Tachash, which had one horn on its forehead, was Tahor.

Etz Yosef (30b, citing Toras Chayim Chulin 60a): Adam ha'Rishon was Kofer b'Ikar, like it says in Sanhedrin. i.e. he thought that the world always existed. Hash-m ate from Eitz ha'Da'as and created the world, like the snake said. A Korban is Nefesh Tachas Nefesh. When Adam admitted to his mistake of denying the Unity of the world, since his sin was in thought, from the brain, he brought a Korban with one horn in the middle of the head, the place of the brain, to atone for this.