Reptile evolution
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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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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.


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


  • 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???)


Living anapsids = chelonia, the turtles

Shoulder girdle inside shell, which is ribs and vertebrae!!


Skull is anapsid = no hole

But has a notch at back which serves the same purpose, accommodate the jaw muscles.


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


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


Lepidosaurs: snakes, lizards


Start out diapsid (two holes behind the eye

In snakes, one opening, and extra hinges in jaw.


Archosaurs = major dinosaur groups

Plus crocodiles, and bird ancestry.


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


Pterosaurs = hang glider wings.


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


Allometry: changes in proportion with growth.

Means young often considered different species from adults.


Stegosaurus; plate back

Functions:?

courtship

thermoregulation?


Crocodiles; surviving archosaurs, in past many terrestrial.


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