Carbon (n): a chemical element that forms diamonds and coal and that is found in petroleum and in all living plants and animals.
The key to identifying the various species of plants, animals and humans, is the detection of a carbon base in that life form. You don’t have to look any further than the iconic sci-fi series, Star Trek, to see this scientific fact applied successfully to the science fiction genre.
As Captain Kirk and his crew spend time seeking out new life and new civilizations, they discover new species of life forms that are not carbon-based. These are some of the first interactions between carbon and non-carbon based life forms.
The possibilities are almost limitless for a writer that introduces a new species that is not carbon based into their storytelling. These non-carbon based life forms open up all sorts of options for developing interactions between the species of your protagonist and these new life forms.
The best part is, the only limitation to creating a new species in science fiction novels, is the mind of the author. A blank page in front of them, the writer can now create the sociology and history of whole new sets of species, and weave them into their story line. This new species develops into a new muse for the writer to thicken the plot of the dilemma their protagonist is facing.