The skull of the Avian is actually the skull of a juvenile giraffe. Making them extinct was a clever way of not having to depict this bird-like race on screen (which would have been both difficult and costly), but also to illustrate the desperate state of Xindi civilization.
This episode was nominated for an Emmy Award for Outstanding Special Visual Effects for a Series but lost out to Countdown (2004).
The names of Dolim (Xindi-Reptilian), Jannar (Xindi-Arboreal) and Kiaphet Amman'sor (Xindi-Aquatic) are revealed in this episode. The name of the main Xindi-Insectoid councilor is mentioned as being long and difficult to pronounce (although novelizations of Enterprise use the name "Shresht"). The Xindi-Primate played by Tucker Smallwood never received an official name by the writers, so Smallwood half-jokingly came up with the name "Depac", after Deepak Chopra. The novelizations give his character the name "Mallora", however.
The first mention of the Vulcan axiom: The needs of the many outweigh the needs of the few. This would be repeated by Spock in Star Trek II: The Wrath of Khan (1982), again in Star Trek III: The Search for Spock (1984), then by Spock's mother at the beginning of Star Trek IV: The Voyage Home (1986).
T'Pol's words echo those of Spock in Star Trek II: The Wrath of Khan (1982) when she tells Reed about the Vulcan saying "The needs of the many outweigh the needs of the few."