Male bristlenose are the ones that get the bristles. While females can also get them, it's far more common for them to remain without, or only get very small spikes that occur just around their mouth. Where did you get the pleco? What were you told it was? If from a store, what was it labeled as? If it was just labeled as "plecostomus", it's almost always going to be a common pleco. Bristlenose on the other hand will go by "ancistrus" (species name), "bushynose", "brushnose", "spineynose" or some other name describing the fact that they get bristles. Even in the bad stores, they usually get that much right, if only because they can bump up the price on them.
My best guess is that it's a common pleco though, as I had a full grown 5" bristlenose, and it had a much different overall shape to it. The one you posted looks younger and more juvenile as far as it's body proportions are concerned, IMO.