Leedsichthys was discovered in 1880s by Alfred Nicholson Leeds in England. Named after Leeds, meaning "Leeds' fish" in Greek. Type species is Leedsichthys problematicus, found in Callovian period
Sharks shed approximately 35,000 teeth in their lifetime. Teeth contain resistant calcium phosphate materials. Teeth are counted along jaw rows and series inward. Young sharks can replace teeth weekly
Tadpole is amphibian's larval stage, most aquatic, some terrestrial. Has fish-like features like lateral line, gills, and swimming tail. Newly hatched tadpoles have external gills covered by skin. Cartilaginous skeleton and notochord develop into spinal cord
Tiktaalik was a 375-million-year-old fishapod found in Arctic Canada. Named "large freshwater fish" by Inuit elders, specifically "Tiktaalik roseae". Estimated length ranged from 1.25 to 2.75 meters. Had triangular head, flat skull, and unique cleaver-shaped fins
Marlins belong to family Istiophoridae, which includes 11 species. Name derived from resemblance to sailor's marlinspike. Have elongated bodies, spear-like snouts, and forward-extending dorsal fins. Among fastest marine swimmers, though speed claims often exaggerated
Cetaceans are mammals with lungs, live birth, streamlined bodies, and fluke. Unlike sea otters and pinnipeds, cetaceans lacked hind legs