Extant chondrichthyans range in size from the 10 cm (3.9 in) finless sleeper ray to the over 10 m (33 ft) whale shark.

[9] As they do not have bone marrow, red blood cells are produced in the spleen and the epigonal organ (special tissue around the gonads, which is also thought to play a role in the immune system).

Apart from electric rays, which have a thick and flabby body, with soft, loose skin, chondrichthyans have tough skin covered with dermal teeth (again, Holocephali is an exception, as the teeth are lost in adults, only kept on the clasping organ seen on the caudal ventral surface of the male), also called placoid scales (or dermal denticles), making it feel like sandpaper.

In later forms, each pair of fins became ventrally connected in the middle when scapulocoracoid and puboischiadic bars evolved.

This is most likely a secondary evolved characteristic, which means there is not necessarily a connection between the teeth and the original dermal scales.

Ampullae of Lorenzini are a network of small jelly filled pores called electroreceptors which help the fish sense electric fields in water.

The lateral line system has modified epithelial cells located externally which sense motion, vibration, and pressure in the water around them.

[14] Capture-induced parturition is often mistaken for natural birth by recreational fishers and is rarely considered in commercial fisheries management despite being shown to occur in at least 12% of live bearing sharks and rays (88 species to date).

The record is extensive, but most fossils are teeth, and the body forms of numerous species are not known, or at best poorly understood.

[18] In particular, new phylogenetic studies find cartilaginous fish to be well nested among acanthodians, with Doliodus and Tamiobatis being the closest relatives to Chondrichthyes.

[20] Dating back to the Middle and Late Ordovician Period, many isolated scales, made of dentine and bone, have a structure and growth form that is chondrichthyan-like.

[21][22][23] The earliest unequivocal fossils of acanthodian-grade cartilaginous fishes are Qianodus and Fanjingshania from the early Silurian (Aeronian) of Guizhou, China around 439 million years ago, which are also the oldest unambiguous remains of any jawed vertebrates.

[24][25] Shenacanthus vermiformis, which lived 436 million years ago, had thoracic armour plates resembling those of placoderms.

The modern bony fishes, class Osteichthyes, appeared in the late Silurian or early Devonian, about 416 million years ago.