These Ithenites were only mentioned in dialogue.
The Ithenites had probably made first contact with Earth sometime prior to 2154, since it is unlikely that Daniels would deliberately contaminate the timeline further by mentioning an alien race Archer hadn't heard of.
An unshot scene from the ENT: "Terra Prime" script included a character called "Karash", an Ithanite [sic] ambassador attending the conference on Earth. He is described as a diminutive, copper-skinned alien. This was supposed to be the same alien species as seen in TOS: "Journey to Babel" who were named "Dayen" in issue 11 of Stardate magazine.