5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

- Tetrapods350 mya

417 mya

Devonian

Radiation of the “stem tetrapods” !!!

Carboniferous

a fish

Old friends

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

- Tetrapods

Caecilians

Salamanders

Frogs

The amniotic egg was a big advance

- amnion protects the embryo - yolk sac provides nourishment - allantoic sac holds waste produced by embryo

Resist desiccation

Provision embryo

allows for colonization of dry habitats

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

Amniote ancestor

Hylonomus

Casineria

ANAPSID (turtles?)

DIAPSID

SYNAPSID

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

The Permian

Formation of Pangaea dries the landscape; amniotes dominate like the gymnosperms.

shelled egg and the seed

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

The Permian

The synapsids radiate and dominate

Mammals

Cynodonts

Gorgonopsids

Therapsids

Pelycosaurs

Dicynodonts

Dimetrodon – a Pelycosaur

A cynodont

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

Mammals

- excellent transitional sequences from cynodont ‘reptiles’ - first fossils with all mammalian features (jaw, ear, dentition, fur) date to ~200 mya - Morganucodontids

Radiations of Mammals

They diversify during the Mesozoic, but the modern groups radiate and dominate in the Cenozoic

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

Mammals

- Monotremes: lay eggs, “sweat” milk

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

Mammals

- Monotremes: egg laying, “sweat” milk

- Marsupials: live birth to embryo – attaches to nipple to complete development. Mother does not need to abandon the nest/young to feed.

Pygmy possum – Australia(opossums in Western Hemisphere)

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

Mammals

- Monotremes: egg laying, “sweat” milk

- Marsupials: live birth to embryo – attaches to nipple to complete development. Mother does not need to abandon the nest/young to feed.

- Placentals: Longer internal development allows for precocial behavior (independence on birth); placental allows for direct, energy-efficient transfer of nutrients between blood systems of mother and offspring.

FOOD DIGESTION

Nutrients in bloodstream of mother

Milk production in mammary glands

FOOD for OFFSPRING

DIGESTION

Nutrients in bloodstream of offspring

Placenta

Each energy transformation is less than 100% efficient

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

Mammals

- Monotremes: egg laying, “sweat” milk

- Marsupials: live birth to embryo – attaches to nipple to complete development. Mother does not need to abandon the nest/young to feed.

- Placentals: Longer internal development allows for precocial behavior (independence on birth); placental allows for more direct and energy-efficient nutrient transfer

precocialaltricial

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

In the Mesozoic, the synapsids are replaced by the great diapsid radiations of Ichthyosaurs, Pterosaurs, and Dinosaurs

Diapsida

Younginiformes

Ichthyosaurs

Lepidosaurs: Lizards, Snakes, Sphenodonts)

Archosaurs: Dinosaurs, Pterosaurs, Crocodilians, Birds

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes - Archosaurs

Crocodilians

Pterosaurs

Dinosaurs

Ornithiscians

Saurischians

Sauropods

Theropods Carnosaurs

Birds

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

Birds: (derived traits)

No teeth

Feathers and endothermy

flight feathers

keeled breastbone

Clavicles united into wishbone

Pneumatic skeleton (houses air sacs from respiratory system)

Unidirectional respiration

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes

In the Mesozoic, the synapsids are replaced by the great diapsid radiations of Ichthyosaurs, Pterosaurs, and Dinosaurs

Diapsida

Younginiformes

Ichthyosaurs

Lepidosaurs: Lizards, Snakes, Sphenodonts)

Archosaurs: Dinosaurs, Pterosaurs, Crocodilians, Birds

Keuhniosaurs

Rhynchocephalians (Tuatara)

Squamates

Scales, moveable quadrate (double hinged jaw), hinged skull

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes - Lepidosaurs

5. Major PhylaDeuterostomes: l. Chordata

Vertebrata Gnathostomes

Tetrapods - Amniotes - Lepidosaurs - Squamates