The simplest test for a ray is where the gill slits sit. In sharks they open on the sides of the head; in rays they open on the ventral surface, and the pectoral fins are fused to the head in front of them. Guitarfish pass that test despite a slim body, two clear dorsal fins and a strong shark-like tail.
Molecular and morphological work places guitarfish, wedgefish, banjo rays and sawfishes together in the order Rhinopristiformes. The sawfishes are not aberrant sharks that acquired a saw but guitarfish relatives whose snout became a toothed blade.
That grouping now carries a grim distinction: the rhinopristiforms include a higher proportion of threatened species than any other order of cartilaginous fishes. Their shallow, soft-bottom habitat overlaps with trawl and gillnet fisheries, and their fins are highly valued in trade.