*they are marine animals with streamlined body.
*they have cartilaginous endoskeleton
*mouth is located ventrally
*notochord is persistent throughout life
*gills slit are separate and without operculum(gills cover)
*skin is tough and have placoid scales
*teeth are modified placoid,and very strong jaws
*they lack air bladder, hence the have to swim constantly
*heart is two chambered
*some of them have electric organ
*some possess poison sting
*they are cold blooded.
*sexes are separate
*fertilization is internal
*e.g.-Scoliodon, Prestis,Trygon
*they have cartilaginous endoskeleton
*mouth is located ventrally
*notochord is persistent throughout life
*gills slit are separate and without operculum(gills cover)
*skin is tough and have placoid scales
*teeth are modified placoid,and very strong jaws
*they lack air bladder, hence the have to swim constantly
*heart is two chambered
*some of them have electric organ
*some possess poison sting
*they are cold blooded.
*sexes are separate
*fertilization is internal
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