The pak'ma'ra (the lower-case spelling is canonical) are a fictional race of aliens in the Babylon 5 universe. They do not feature heavily in any storylines, partly on the pretext that other species avoid them because they are, for religious reasons, dedicated carrion eaters.
Humanoid in form, the pak'ma'ra have tentacles around a mouth cavity containing an inflexible beak. Michael Garibaldi describes them as resembling "an octopus that got run over by a truck." They rely on machine translation for interspecies communication. However, Durhan commented once that they refuse to learn any language other than their own. They are capable of singing what several other races considered extremely beautiful music, but only do so on religious holidays.
Until its dissolution, the pak'ma'ra were members of the League of Non-Aligned Worlds, with an ambassador on Babylon 5. They then became members of the Interstellar Alliance. The pak'ma'ra took on the role as couriers for the ISA Rangers because of the distaste other species had for them, and their tendency to be on every major world in numbers but be ignored.
The pak'ma'ra were one of the few other races to be susceptible to the Drafa Plague, though, unlike the Markab, their numbers were not threatened by Second Outbreak in 2259 as a vaccine was developed before the population was seriously threatened.
The pak'ma'ra believe themselves a chosen and superior people, and their ability to consume any other of the sentient species is a sign of this.
The most commonly referenced aspect of the pak'ma'ra in the series is their diet of carrion, which all other major species consider repugnant. They are fond of eating the corpses of sentient species, and it has been insinuated they will steal bodies in order to do so (although this might just be a rumor based on other species' xenophobia). Due to their eating habits, the pak'ma'ra have shown themselves incredibly resistant to food poisoning and disease from rotten meat. However, they are easily nauseated by things outside their preferred diet - to the point of projectile vomiting.