Nurse sharks show a strong preference for certain resting sites, and repeatedly return to the same caves and crevices after a nocturnal activity. Biology Distinctive Features Nurse sharks have two spineless, rounded dorsal fins with the first dorsal fin much larger than second, and one anal fin. The origin of the first dorsal fin is about over the origin of the pelvic fin. The caudal fin is more than of the total animal length. The sub-terminal mouth is placed well in front of the eyes, the spiracles are minute, and moderately long barbels reach the mouth.
Nasoral grooves are present, but there is no perinasal groove.
4 part 1. Nurse sharks possess independent dentition, the simplest type of tooth arrangement found in sharks. This means that there is no overlap between teeth, and that forward movements of teeth leading to shedding does not depend on other teeth. In sharks with various degree of overlapping dentition, replacement of teeth cannot take place until outer blocking teeth are lost. Replacement rates among juveniles are generally faster than for adults.