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Reptile Evolution

Reptile Evolution. Origin of derivatives. Ancestral reptile = anapsid , small, legs out to sides. A brief look at Classification. “Old view” = Amphibians give rise to reptiles, reptiles give rise to birds and mammals phyletic patterns.

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Reptile Evolution

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  1. Reptile Evolution Origin of derivatives

  2. Ancestral reptile = anapsid , small, legs out to sides.

  3. A brief look at Classification “Old view” = Amphibians give rise to reptiles, reptiles give rise to birds and mammals phyletic patterns.

  4. Major radiation into all ways of life; terrestrial, aquatic, aerial.

  5. New View of Taxonomy = Cladistics common derived characteristics • Problem with reptiles = heart structure. • fossil reptiles that give rise to mammals appear early in • reptile history and leave no descendents • modern reptiles heart structure is different from mammal structure, so cant derive modern mammals from modern reptiles. • so in Cladistics, kick mammal ancestors out of the reptiles • (if it looks like a lizard, it is a lizard???)

  6. Living anapsids = chelonia, the turtles Shoulder girdle inside shell, which is ribs and vertebrae!!

  7. Skull is anapsid = no hole But has a notch at back which serves the same purpose, accommodate the jaw muscles.

  8. Ichthyosaurs: fully aquatic, but air breathing. A reptile equivalent to whales or porpoises. Mostly fish eating.

  9. Plesiosaurs; snake neck strung through a turtle body. Came on land to lay eggs probably.

  10. Lepidosaurs: snakes, lizards

  11. Start out diapsid (two holes behind the eye In snakes, one opening, and extra hinges in jaw.

  12. Archosaurs = major dinosaur groups Plus crocodiles, and bird ancestry.

  13. A very diverse and complex group. - die out at Cretaceous boundary = meteor?

  14. Pterosaurs = hang glider wings.

  15. Archosaurs: wide variety, carnivorous, plant eaters, now known to be social, etc.

  16. Allometry: changes in proportion with growth. Means young often considered different species from adults.

  17. Stegosaurus; plate back Functions:? courtship thermoregulation?

  18. Crocodiles; surviving archosaurs, in past many terrestrial.

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