Chimaera © Magnus Lundgren.

Chimaeras are closely related to sharks, skates and rays, belonging to the same class Chondrichthyes. But whereas sharks, skates and rays branch off into their own subclass Elasmobranchii, the chimearas form their own subclass Holocephali. When we refer to ‘sharks’ in the broader term we also include the chimaeras.

The chimaera fishes are characterised by long, tapering bodies and very large heads. Most notably they have an upper jaw which is fused to the upper part of the skull and non-replaceable teeth which are fused into three pairs of hyper-mineralised tooth plates. The mouth is positioned on the underside of the head, connected to the nostrils by deep groves. Due to the incisor like tooth plates and large nostrils, the mouth is said to resemble a rabbits, hence these fish are sometimes given the nickname rabbitfish.

Chimaeras have a cartilaginous skeleton and their skin is smooth, lacking scales with colour ranging from black to brownish grey. They usually have an enlarged translucent green eye due to the lack of light in their deep sea habitat. The majority of chimaeras have a unique defence mechanism in the form of a venomous spine located in front of the dorsal fin. They have two dorsal fins, pectoral and pelvic fins with delicate external fin webs. Males and females are very different in appearance, with males possessing a number of secondary sexual structures, including frontal and pelvic appendages and paired pelvic claspers. The frontal appendage is equipped with several sharp denticles assumed to play a role in mating. These additional sexual structures develop once sexual maturity has been reached.

There are 37 species in the single order of chimaeriformes with many new species awaiting formal description. Their bathymetric distributions are quite broad; occurring along the shelf and slope from the intertidal, from less than 500 to over 2,500m in depth.

Related Links:

Chimaera Taxonomy

Chimaera Diet

Chimaera Reproduction

Chimaera Distribution

Chimaera Conservation