These animals are collectively referred to as elasmobranchs because they are in the Class Elasmobranchii (older classification systems refer to these organisms as Class Chondrichthyes, listing Elasmobranchii as a subclass.) According to the World Register of Marine Species (WoRMS), elasmobranch comes from elasmos (Greek for "metal plate") and branchus (Latin for "gill").
Characteristics of Elasmobranchs:
- Skeleton made of cartilage
- 5-7 gill openings on each side
- Rigid dorsal fins (and spines if present)
- Spiracles to aid in breathing
- Placoid scales (dermal denticles)
- The upper jaw of elasmobranchs is not fused to their skull.
- Elasmobranchs have several rows of teeth which are continually replaced.
Elasmobranchs reproduce sexually with internal fertilization and either bear live young or lay eggs.