Cranial and caudal neuropores become progressively smaller until they close completely (by day 26) forming the neural tube.

There are two dorsal fins, no anal fin, and unusually for sharks, the lower lobe of the caudal fin is longer than the upper lobe.

In the cephalic portion, the germ layer shows specific differentiation at the beginning of the 4th week, while in the caudal portion it occurs at the end of the 4th week.

Somites form one after the other down the length of the embryo from the head to the tail, with each new somite forming on the caudal (tail) side of those already in existing somites.