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.
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
Major radiation into all ways of life; terrestrial, aquatic, aerial.
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
Crocodiles; surviving archosaurs, in past many terrestrial.