- Superclass: Gnathostomata “jaw
Transcription
- Superclass: Gnathostomata “jaw
- Superclass: Gnathostomata “jaw-mouthed vertebrates” ~430 million years ago • Two new characteristics: • Jaw - Allows consumption of larger, more diverse prey. • Paired fins - at least two sets of paired fins: pectoral and pelvic. Gives stability and lift, prevents roll. roll Mandibular arch Hyoid arch Gill arches pitch yaw • Big evolutionary radiation after advent of first jawed fish... – Acanthodians – Placoderms – Chondrichthyes – Sarcopterygii – Actinopterygii • Phylum Chordata – Subphylum Urochordata (Tunicata) – Subphylum Cephalochordata – Subphylum Craniata -Vertebrata • Superclass Agnatha • Superclass Gnathostomata – – – – – – – – Class Placodermi Class Chondrichthyes Class Acanthodii Class Osteichthyes Class Amphibia Class Reptilia Class Mammalia Class Aves Acanthodians • Body armor like ostracoderms, fins w/spines • Skeleton had some bone (p.63) Placoderms - “plate-skinned” fish placoderm skull • Bony plates are in smaller pieces compared to ostracoderms • Mostly fed on bottom, some mid-level predators Chondrichthyes • Sharks, skates and rays Placoid scales Ampullary organs (p.59) 1 fossil shows live birth Chondrichthyes • Heterocercal vs. Homocercal tails • No swim bladder for buoyancy Heterocercal – big liver – loss of weight – lift from tail, pectoral fins Homocercal • Teeth in shark originate from modified placoid scales Enamel Dentine ‘Denticles’ Chondrichthyes Septal gill design • Phylum Chordata – Subphylum Urochordata (Tunicata) – Subphylum Cephalochordata – Subphylum Craniata -Vertebrata • Superclass Agnatha • Superclass Gnathostomata – – – – – – – – Class Placodermi Class Chondrichthyes Class Acanthodii Class Osteichthyes Class Amphibia Class Reptilia Class Mammalia Class Aves Osteichthyes Swim bladder • “Bony fish” • By far the most diverse class. • Swim bladder (or gas bladder) present in most species • Opercular gills - bony covering overlying gill slits Some major groupings in Osteichthyes • Actinopterygii – Teleostei • Sarcopterygii – Dipnoi – Crossopterygii 2 major groups: • Actinopterygians - ray-finned fish – dominant form presently – fins move via muscles in body wall – fins w/ Lepidotrichia • Sarcopterygians - fleshy-finned fish – Thicker fins - muscles within fins – Swim bladder connected to gut (ancestral) – Internal nostril (choana) first arose in this group fossil sarcopterygian w/choana Early choanates Actinopterygii • Teleosts - diverse group of Actinopterygians – Recent radiation - 65 million years ago – Has a derived swim bladder design (detached from gut) Sarcopterygii • Dipnoi - lungfish – Paired lungs – Survive in mud by breathing air. – In warm waters - not as much dissolved oxygen Sarcopterygii • Crossopterygii – Several fossil forms with swim bladders used as “lungs” – One living - Coelacanth Fossil organisms showing a fish/tetrapod transition Acanthostega Tiktaalik roseae “Labyrinthodont” group • Crossopterygii • Homologies with Amphibia – Bones in fins correspond to bones in early tetrapods – Labyrithodont teeth From water to land: “Problems”: Support - Air is a thinner medium. Gas exchange - Oxygen in a different state. Temperature - Fluctuates more in air. Keeping moist - How to keep tissues, eggs, young moist? Amphibia - have aquatic larval stage • • • Toads and Frogs (Anura) Salmanders (Urodela) Caecilians (Gymnophiona) • Phylum Chordata – Subphylum Urochordata (Tunicata) – Subphylum Cephalochordata – Subphylum Craniata -Vertebrata • Superclass Agnatha • Superclass Gnathostomata – – – – – – – – Class Placodermi Class Chondrichthyes Class Acanthodii Class Osteichthyes Class Amphibia Class Reptilia Class Mammalia Class Aves Tetrapods Amniotes Amniotes • Amniotes - have embryos with extraembryonic membranes – amnion keeps water from leaving the egg or developing young. Major living ‘reptile’ groups: • Lizards and snakes (Squamata) • Crocodiles and alligators (Crocodilia) • Turtles (Testudinata) Aves • Most diverse class of tetrapods Endothermy • Feathers • Puts particular requirements on some physiological systems: – modification of skin – thermoregulation, flight Mammalia Defining characteristics: • Hair - for insulation, sensation. • Circulatory, respiratory systems must be efficient and work at high rates Distinguishing mammal from reptile fossils • Via fossil evidence: 1. Three bones make up middle ear: malleus, incus, stapes • Mammary glands • Other glands - sweat and sebaceous glands. Theraspid Distinguishing mammal from reptile fossils 2. Lower jaw a single bone (dentary) Major mammal groups: • Monotremes - oviparous 3. Jaw joint is articulation of dentary and squamosal bone. Therians - viviparous • Marsupials - partial internal - external development Therians - viviparous • Placentals (eutherians) - completely internal development - Most diverse
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