Elasmobranchii

Elasmobranchii is a subclass of Chondrichthyes, or cartilaginous fish, that includes the sharks, rays, and skates. The name "Elasmobranchii" comes from the Greek words elasmos (meaning "plate") and brancho (meaning "gill"), referring to the fact that these animals have gill plates instead of gill slits.

Characteristics

Elasmobranchs are characterized by their cartilaginous skeletons, which are lighter and more flexible than bone. They also have several other unique features, such as their skin, which is covered in tiny tooth-like scales called dermal denticles. These scales provide protection and reduce friction when swimming.

Evolution

The Elasmobranchii subclass is believed to have evolved around 400 million years ago, during the Devonian period. They have since diversified into over 1,000 species, ranging from the tiny dwarf lanternshark to the massive whale shark.

Reproduction

Elasmobranchs exhibit a variety of reproductive strategies. Some species lay eggs (oviparity), while others give live birth (viviparity). Many species also exhibit ovoviviparity, where the eggs hatch inside the mother's body.

Conservation

Many species of elasmobranchs are threatened by human activities such as overfishing and habitat destruction. Conservation efforts are underway to protect these species and their habitats.

See also

• Chondrichthyes
• Shark
• Ray
• Skate

References

• 
  Great White Shark
• 
  Basking Shark