Size: Adults can reach a maximum length of 41.1 cm.
Coloration: The appearance of P. paru differs greatly between juveniles and adults. Young P. paru are a dark brown to black color with thick, curved yellow bands across the head and body. As an adult, the yellow bands fade except for one yellow bar at the outer base of the pectoral fin. The scales turn black with yellow rims and the face becomes light blue with a white chin and mouth region.
Body shape: The disc-shaped Angelfish family is distinguished by a strong, curved, projecting spine on the lower edge of the preopercle bone and the absence of a pelvic axillary process. On juveniles, the spine is serrate and smoothes out in the adult form. The stout spine found on the gill cover gives P. paru its name (Pom= "cover", acanthus= "spine"), and distinguishes them from the closely related butterflyfishes (Allen 1985, Helfman 1997, Nelson 1999).