Class Chondrichthyes

Class ChondrichthyesKingdom: AnimaliaPhylum: ChordataSubphylum: VertebrataClass: ChondrichthyesSubclass: HolocephaliSubclass: ElasmobranchiiSuperorder BatoideaSuperorder SelachimorphaCartilaginous FishIncludes: SharksRaysSkatesRatfish/Chimeras/Ghost fish

General Characteristics:Jawed fishSkeleton made of cartilageLack swim bladderTeeth & vertebrae sometimes calcified

General Characteristics:Possess movable jawsMouth is ventral, underneath the headCountershading the ventral sides are light colored while the dorsal sides are darker creating a simple camouflage

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

5EvolutionMegalodonAncient SharkLargest predatory fish everTwice the size of a Great White

Subclass HolocephaliIncludes: Ratfish/ChimerasDeep water fishLarge head & eyesGill slits covered by a flap of skinNo scales, skin insteadCaudal fin developed into rat-like tailEats crustaceans & mollusks

Subclass ElasmobranchiiIncludes: Sharks, Rays, & SkatesDenticles streamlined scales made of the same material as their teeth

Energy Efficiency:Cartilage skeleton make them lighter, thus takes less energy to remain buoyantBuoyant oils in liverFins at angles to provide liftSkin elasticity transfers energy to tailScales reduce friction (smooth towards tail, rough towards head)Store urea to maintain similar density to water

Superorder BatoideaIncludes: Skates, Rays, & SawfishFlattened bodyDemersal live on the ocean floorGill slits on ventral (bottom) side

10Skates & RaysPectoral fins are flat and expandedHead fuses with pectoral fins with eyes on top

Skates vs. Rays

Stingrays

Equipped with a stinging spineSpine connected to venomous glandsTeeth modified into grinding plates13Manta & Devil RaysNot bottom dwellers instead choose to swim

14Sawfish vs. SawsharkSawfish categorized with the rays while sawshark categorized with the sharksSawfish have ventral gill slits, smaller and flatter bodySawshark have gill slits on the side, rounded body, bigger overall, and presence of barbels

Superorder SelachimorphaIncludes: SharksGill slits on the sidePaired & unpaired finsMost are quite mobile and designed for fast swimming

16Paired vs. Unpaired finsPaired: Pectoral & PelvicComparable to our arms and legsUnpaired: 1st Dorsal, 2nd Dorsal, Anal, and CaudalAll found along mid-line

17Scales

Scales are very small and sharpSame composition as the teeth18JawsMade of boneContain the disposable teethIn some species capable of extending jaw out from body

19TeethSame composition as the scalesContinually shed and replaced by the rows behind

20Respiration

Must swim to force water through their gillsSome 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 functions21Digestion

Very short esophogusStomach can be up to 1/3 the length of the sharkIntestine is really small, only about a foot22Nervous SystemLateral line used for sensing vibrations in the water

23Nervous SystemAmpullae of LorenziniJelly filled canals that can detect electrical fields, magnetic fields, temperature, salinity, water pressure, etc.Electroreception

24Nervous SystemPaired external nostrils that lead directly to the brainVery acute sense of smell, can detect concentrations as low as one part per billion

25Shark ClassificationTwo Sub-Orders:Galeomorphs & SqualomorphsFurther broken down into orders

26Order Heterodontiformes:

Bullhead SharksPig like snoutBottom dwellers27Order Orectolobiformes:Carpet SharksVery short mouthsUpper lobe of caudal fin extended with reduced lower lobeIncludes filter feeders

28Order Lamniformes:Mackerel FishLarger front teethInclude some of most popularMost are active predatorsFunctionally warm-blooded

29Order Lamniformes:Goblin SharksMitsukurindidae

Sandtiger SharksCarchariidae

30Order Lamniformes:

Ragged-Tooth SharksOdontaspididae

Thresher SharksAlopiidae31Order Lamniformes:Megamouth SharkMegachasmidae

Crocodile SharksPseudocarchariidae

32Order Lamniformes:

Basking SharkCetorhinidae

Mackerel SharksLamnidae33Order Carcharhiniformes:

Ground or Whaler SharksAdaptable to many environments, even estuarine and freshwater Flappable lower eyelids34Order Carcharhiniformes:Whaler SharksCarcharhinidae

Hammerhead SharksSphyrnidae

35Order Carcharhiniformes:

Cat SharksSchliorhinidae36Order ChlamydoselachiFrilled SharkEel like bodyTeeth are three prongedDeep water

37Order Hexanchiformes

Cow SharksDeep waterVery little is known38Order EchinorhiniformesBramble SharksThick tail stalkHas bumps on skinhedgehog shark

39Order Sqauliformes

Dogfish SharksLarge ranges of sizesGenerally best known shark40Order SqauliformesGreenland Shark (21 feet +)

Dwarf Laternshark

41Order Squantiniformes

Angel SharksFlattened bodiesGills on ventral sideMouth at end rather than ventral like rays and skates42Order Pristiophoriformes

SawsharksSimilar to sawfish, but skinnier and have sensitive barbs on snoutAlternating long short teeth43