Class Chondrichthyes Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Chondrichthyes Subclass: Holocephali Subclass: Elasmobranchii Superorder Batoidea Superorder Selachimorpha

Cartilaginous Fish Includes: Sharks Rays Skates Ratfish/Chimeras/Ghost fish

General Characteristics: Jawed fish Skeleton made of cartilage Lack swim bladder Teeth & vertebrae sometimes calcified

General Characteristics: Possess movable jaws Mouth is ventral, underneath the head Countershading – the ventral sides are light colored while the dorsal sides are darker creating a simple camouflage

Evolution: Earliest relatives found in the Devonian Age Modern looking sharks first appear in the Jurassic Era

Evolution Megalodon Ancient Shark Largest predatory fish ever Twice the size of a Great White

Subclass Holocephali Includes: Ratfish/Chimeras Deep water fish Large head & eyes Gill slits covered by a flap of skin No scales, skin instead Caudal fin developed into “rat-like” tail Eats crustaceans & mollusks

Subclass Elasmobranchii Includes: Sharks, Rays, & Skates Denticles – streamlined scales made of the same material as their teeth

Energy Efficiency: Cartilage skeleton make them lighter, thus takes less energy to remain buoyant Buoyant oils in liver Fins at angles to provide lift Skin elasticity transfers energy to tail Scales reduce friction (smooth towards tail, rough towards head) Store urea to maintain similar density to water

Superorder Batoidea Includes: Skates, Rays, & Sawfish Flattened body Demersal – live on the ocean floor Gill slits on ventral (bottom) side

Skates & Rays Pectoral fins are flat and expanded Head fuses with pectoral fins with eyes on top

Skates vs. Rays

Stingrays Equipped with a stinging spine Spine connected to venomous glands Teeth modified into grinding plates

Manta & Devil Rays Not bottom dwellers instead choose to swim

Sawfish vs. Sawshark Sawfish categorized with the rays while sawshark categorized with the sharks Sawfish have ventral gill slits, smaller and flatter body Sawshark have gill slits on the side, rounded body, bigger overall, and presence of barbels

Superorder Selachimorpha Includes: Sharks Gill slits on the side Paired & unpaired fins Most are quite mobile and designed for fast swimming

Paired vs. Unpaired fins Paired: Pectoral & Pelvic Comparable to our arms and legs Unpaired: 1st Dorsal, 2nd Dorsal, Anal, and Caudal All found along mid-line

Scales Scales are very small and sharp Same composition as the teeth

Jaws Made of bone Contain the disposable teeth In some species capable of extending jaw out from body

Teeth Same composition as the scales Continually shed and replaced by the rows behind

Respiration Must swim to force water through their gills Some such as nurse sharks can get enough oxygen so they do not need to swim (pumping mechanism) Sharks that do not have this mechanism go through active periods and rest periods where they lower body functions

Digestion Very short esophogus Stomach can be up to 1/3 the length of the shark Intestine is really small, only about a foot

Nervous System Lateral line used for sensing vibrations in the water

Nervous System Ampullae of Lorenzini Jelly filled canals that can detect electrical fields, magnetic fields, temperature, salinity, water pressure, etc. Electroreception

Nervous System Paired external nostrils that lead directly to the brain Very acute sense of smell, can detect concentrations as low as one part per billion

Shark Classification Two Sub-Orders: Further broken down into orders Galeomorphs & Squalomorphs Further broken down into orders

Order Heterodontiformes: Bullhead Sharks Pig like snout Bottom dwellers

Order Orectolobiformes: “Carpet Sharks” Very short mouths Upper lobe of caudal fin extended with reduced lower lobe Includes filter feeders

Order Lamniformes: “Mackerel Fish” Larger front teeth Include some of most popular Most are active predators Functionally warm-blooded

Order Lamniformes: “Goblin Sharks” Mitsukurindidae “Sandtiger Sharks” Carchariidae

Order Lamniformes: “Ragged-Tooth Sharks” Odontaspididae “Thresher Sharks” Alopiidae

Order Lamniformes: “Megamouth Shark” Megachasmidae “Crocodile Sharks” Pseudocarchariidae

Order Lamniformes: “Basking Shark” Cetorhinidae “Mackerel Sharks” Lamnidae

Order Carcharhiniformes: “Ground or Whaler Sharks” Adaptable to many environments, even estuarine and freshwater Flappable lower eyelids

Order Carcharhiniformes: “Whaler Sharks” Carcharhinidae “Hammerhead Sharks” Sphyrnidae

Order Carcharhiniformes: “Cat Sharks” Schliorhinidae

Order Chlamydoselachi “Frilled Shark” Eel like body Teeth are three pronged Deep water

Order Hexanchiformes “Cow Sharks” Deep water Very little is known

Order Echinorhiniformes “Bramble Sharks” Thick tail stalk Has bumps on skin “hedgehog shark

Order Sqauliformes “Dogfish Sharks” Large ranges of sizes Generally best known shark

Order Sqauliformes Greenland Shark (21 feet +) Dwarf Laternshark

Order Squantiniformes “Angel Sharks” Flattened bodies Gills on ventral side Mouth at end rather than ventral like rays and skates

Order Pristiophoriformes “Sawsharks’ Similar to sawfish, but skinnier and have sensitive barbs on snout Alternating long short teeth