As nouns,
brush-tailed porcupine is a hyponym of
Old World porcupine; that is, brush-tailed porcupine is a
word with a more specific, narrower meaning than
Old World porcupine:
Old World porcupine: terrestrial porcupine
brush-tailed porcupine: porcupine with a tuft of large beaded bristles on the tail