 Dogfish because they turn their head side to side when they swim  Spiny because they have spines near their fins

 K: Animalia  P: Chordata  SP: Vertebrata  C: Condrichthyes  O: Squaliformes  F: Squalidae  G: Squalus  S: S. acanthius

 Sharks have been around for over 300 million years  There are over 300 species of sharks

 Head: broad, flattened  Trunk: fusiform in shape to help with locomotion  Tail: compressed laterally, principal organ of locomotion

 Rostrum: pointed snout at the anterior end of the body, helps overcome water resistance  Nares: external nostrils, located on ventral surface of rostrum, used to detect odors in the water  Jaws: on underside of head, sharp pointed teeth in rows (replaceable),

 Spiracle: modified gill slit, serves in water intake when jaws are grasping food  Eyes: immovable eyelid, can not focus on one object simultaneously  Lateral Line: extends from spiracle to tail, receptor for vibrations and pressure changes

 Pectoral Fins: located ventrolaterally behind the gill slits, helps with manuvering and keeping shark horizontal in water  Pelvic fins: located ventrolaterally at the end of the trunk  Dorsal Fins: unpaired, located on the dorsomedial line, 1 st behind pectoral fin other behind the pelvic line

 Caudal fin: major part of tail, consists of dorsal lobe and ventral lobe of unequal size  Mouth: located subterminally  Teeth: modified placoid scales, arranged in rows, can be replaced

 Endolymphatic Pores: lead to endolymphatic duct, used in equilibrium  Ampullae of Lorenzini: pores in the skin at the top and bottom of head › Functions: electrical potential; hydrostatic pressure, temp gradient, salinity gradient

 Claspers: modified copulatory organs located on the edges of the pelvic fin in adult male sharks  Cloaca: common exit for the digestive, urinary and reproductive systems  Papilla: Males- urogenital papilla, exit for urine and sperm; Females-urinary papilla, exit for urine only

 Abdominal Pore: located on the lateral edges of the cloaca, serves as outlets for excess coelomic fluid

 Placoid Scales: modifications of teeth, embedded in skin pointing caudally  Development is very similar to teeth in higher vertebrates, including humans