- You may also be looking for the Antarians.
The Antarans were an Alpha or Beta Quadrant species, strongly humanoid with a lifespan of at least 90 years upon reaching adulthood.
Antarans have been at war with the Denobulans several times, the last conflict of which took place in the 19th century. However, Antarans continued to strongly dislike Denobulans until at least the 2150s, even though encounters between the two species were extremely rare. This behavior was due to widespread prejudices, as every Antaran was taught from childhood that all Denobulans are enemies to be feared and reviled.
The 19th century dating is derived from Phlox's statement that they had not been at war for 300 years, in 2153.
The Antaran homeworld was quite far from Xantoras, and it would be rare to see one that far away from home. (ENT: "The Breach")