Would writing a novel based on another's species be plagiarism?

Would writing a novel based on the species/races of another novel be plagiarism, if that author was given credit and the story-line, characters, and setting was completely different? Or would it even be necessary to give credit to the author if the only similarity is that there are a few races in common? I'm looking for actual laws to back this up, any help would be appreciated.
Asked Dec 28, 2014

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