Mating and spawning grounds off the cast coast of Canada have not been delineated. Thus, there are no data available on the topography preferred by thorny or smooth skates during the breeding season. The fertilized eggs remain at a very early state of development until egg cases are formed and each egg has migrated into a case. Once the case is fully formed with the eggs inside, development commences. The number of eggs laid increases as the size of the female increases, but it is not unusual for a female to produce between 6 and 40 eggs for each breeding season, depending on the species.
Thorny skates produce egg cases which are flat on one side and strongly convex on the other.
Delicate fibrils extend along each lateral margin. The case size varies widely and samples on the outer Nova Scotia Bank indicate a size range of 77 to 90 mm from females 84 to 102 cm long. Sexual maturity occurs at about 54 cm. Smooth skates become sexually mature at about 50 cm and produce egg cases that are flat on one side and strongly convex on the other. The shell is smooth and the horns which project from each corner are thick and at least as long as the capsule.