An important key factor to understanding these creatures is ageing, many deepwater Apristurus profundorum have poorly calcified vertebrae that lack visible growth bands, and most do not have dorsal fin spines that can be used for ageing.
Ageing plays a significant role in understanding these deepwater Apristurus profundorum. The difficulty in determining their age due to poorly calcified vertebrae lacking growth rings and the absence of suitable dorsal fin spines is highlighted.