Cnissites

Cnissites (/ˈknɪsaɪt/; Old Horil: ^KAKNI-so-om-ka-aš-ka), or cenogaghs (Elvish: кыногафен, cynogafen), were a Chilovakian race who flourished during the Bronze Age between about 1700 and 1200 BCA in what is modern southern Areltya. Very little is known about them, but Horil records indicate they were neither horil nor human. Their own records, what few have survived, are in a form of the Elvish language, but written in Linear Horil. They are generally assumed to represent an extinct anthropoid race.
It's not well understood what happened to the cnissites. The two leading theories, which are not mutually exclusive with each other, are that they were outcompeted by humans and horils and driven to extinction, or that they interbred with humans and horils, disappearing into their populations.