1. The bony or cartilaginous framework that encloses and protects the brain and sense organs of all vertebrates and of one group of nonvertebrates (the hagfishes); cranium. 2. Informal The head, regarded as the seat of thought or intelligence: Use your skull and solve the problem. 3. A...
chordata–lanceletsCephalachordata–lancelets SubphlumVertebrata-vertebratesSubphlumVertebrata-vertebratesSubphylumUrochordataSubphylumUrochordataSeaSquirtsorTunicatesSeaSquirtsorTunicatesUrochordateCharacteristicsUrochordateCharacteristics Haveanon-livingtunicHaveanon-livingtunic MostchordatefeaturesfoundinthefreeMostchord...
Fish Evolution First fishes known were jawless with heavy bony armor Internal skeleton was made of cartilage Survived by lampreys and hagfish (“Agnathans” - no jaws) First jawed fishes occurred 410 million years ago Early jawed fishes were replaced by more agile sharks and bony fishes Jaws ...
butallindividualshaveovitestis,•Eggsdepositedatsea;directdevelopment;totallymarineHagfishcharacteristicsClassAgnathaSubphylumVertebratalampreyLampreyCharacteristics•Oraldisc/buccalfunnel,withepidermaldenticlesandraspingtongue;active"predatoryparasites”•Nobone•Nostrilontopofhead•Well-developedvertebrateeyes•Well...