Dark Piper (1968)

Returning to his home planet after ten years, Griss Lugard found Beltane relatively untouched by the annihilating war of the Four Sectors, her inhabitants still immersed in their experiments in mutation. Lugard's warnings of imminent danger from off-world meant nothing to them.

Only Vere Collis and his friends believed in Lugard and, drawn by his magnetism to explore unknown desert caves, they were safe underground when a series of explosions rocked Beltane, killing Lugard and sealing them in.

After a fearful battle they won their way to the surface, only  to receive a shattering blow:
All other human inhabitants on Beltane had perished - and only strange and possibly hostile mutant creatures awaited them.

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There was no sound to herald its coming - it was suddenly there/ It stood with its head a little to one side, its snout pointed upwards, its shoulders hunched, while above fond-like strips of skin fluttered and stiffened. It was a dead gray-white and was as tall as I.

Skeleton proportions added to its eerie appearance. All four limbs looked to be only scaled skin stretched tightly over angular bones. the head was a skull hardly clothed with flesh, except for the antennae, and its body as lead as if it were in the last stages of starvation.

As a biped, it was somehow more alarming than if it had run on four feet. We are conditioned to associate an upright stance with intelligence, and I had the impression that I was confronted by no mindless beast but something that ruled this dark world.

But there was little time for such impressions - it began to walk directly towards me and those arms, which had looked so weak when compared with the powerful legs, snapped up and out, the clawed paws making ready to take me ...