Credible Aliens?

Are the Kandemirians in Poul Anderson's After Doomsday (St Albans, Herts, 1975) credible aliens? Because of the kind of science fiction (sf) that he wrote, Anderson was continually obliged to invent new rational species for his human characters to interact with.

So far already in this novel we have had avian Monwaingi,  wolverine Vorlakka and arachnid Mayastans although I am confident that, if there are any real aliens, then they will not resemble any Terrestrial organisms. Having for the time being exhausted animal resemblances, a Kandemirian is a seven-foot humanoid with broad shoulders, narrow waist, ovoid head, greenish-blue eyes, slit pupils, a small nose, large pointed ears, much hair, glabrous skin, scent organs in two mobile tendrils on the upper lip and six-fingered hands with black nails. Wearing austere clothes in subdued colours, he strides down a rubbery-floored corridor or squats at a legless desk under the leaves of a large plant.

Tarkamat of Askunzhol who speaks for the Baikush Clan and for the field command of the Grand Fleet smiles and speaks courteously in fluent Uru from his squatting position to a human prisoner of war, addressing him as "shipmaster" (p. 75). Does Tarkamat sound like a large samurai? It is enjoyable to read almost a World War II scenario projected onto an interstellar scale with entire new rational species replacing Terrestrial nationalities but Anderson's later sf recognised that this was unlikely.

There is a rationale for the situation in After Doomsday and other earlier sf novels. If (If) the galaxy is full of intelligent species, then those that have nothing in common will simply disregard each other. However, parallel evolution in similar environments will bring it about that several species are similar enough to communicate and interact. Hence, a squatting Kandemirian smiling and offering a drink to a captured Earthman.