how does a saw fish use its saw
Sawfish The most distinctive feature of sawfish is their saw-like rostrum with a row of whitish teeth (rostal teeth) on either side of it. The rostrum is an extension of the chondrocranium ("skull"),[27] made of cartilage and covered in skin.[33] The rostrum length is typically about one-quarter to one-third of the total length of the fish,[5] but it varies depending on species, and sometimes with age and sex.[1] The rostal teeth are not teeth in the traditional sense, but heavily modified dermal denticles.[34] The rostal teeth grow in size throughout the life of the sawfish and a tooth is not replaced if it is lost.[34][35] In Pristis sawfish the teeth are found along the entire length of the rostrum, but in adult Anoxypristis there are no teeth on the basal one-quarter of the rostrum (about one-sixth in juvenile Anoxypristis).[36][37] The number of teeth varies depending on the species and can range from 14 to 37 on each side of the rostrum.[2][38][note 1] It is common for a sawfish to have slightly different tooth counts on each side of its rostrum (difference typically do not surpass three).[39][40] In some species, females on average have fewer teeth than males.[1][39] Each tooth is peg-like in Pristis sawfish, and flattened and broadly triangular in Anoxypristis.[2] A combination of features, including fins and rostrum, are typically used to separate the species,[2][38] but it is possible to do it by the rostrum alone.[41]