Traits

Overlapping, round scales

Sharp denticles, mutated “teeth”

Rhomboidal, fit together like a jigsaw rather than imbricate

Narrow slits typically open along the neck, and can extend down the line of the ribcage. Range from small semicircles to shaped openings

Gills present on frilled stalks protruding from the head. Range from short nubs to trailing tendrils

Simple webbing and spines

Standard toe length, good for all around swimming

Shortened toes, better for swimming in the shallows

Elongated toes, better for deep-sea swimming

Soft, ray fins.

Cartilaginous fins.