Large reptiles that survived the KT extinction

1. Large reptiles that survived the KT extinction Nicole Prinsloo 2449162 Department of Biodiversity and Conservation Biology, University of the Western Cape

2. A massive extinction event known as the Cretaceous-Tertiary extinction occurred about 65.5 million years ago • This event corresponds to the end of the Cretaceous Period and the beginning of the Tertiary period • The duration of this event is unknown and many species became extinct • Species that became extinct include the non-avian dinosaurs Badlands near Drumheller, Alberta where erosion has exposed the KT boundary.(http:en.wikipedia.org/wiki/Cretaceous-Tertiary_extinction_event)

3. Casualties of the extinction Dinosaurs were the most conspicuous organisms that became extinct Birds were the sole survivors among Dinosauria Mammals also suffered along with marsupials and multituberculates Mosasaurs and plesiosaurs, which were the great sea reptiles of the cretaceous also became extinct (www.google.com)

5. KT extinction theories • Alvarez hypothesis • Chicxulub crater • Decan traps • Multiple impact event • Supernova hypothesis (www.google.com)

6. Reptiles that died out in the KT extinction • Plesiosaurs and mosasaurs, together with large marine turtles became extinct • Turtles had a survival rate of 88% • Ichtyosaurs did not make it to the KT and died during the Cenomanian, thirty million years before the KT A mesosaur (www.google.com)

7. Crocodiles • Crocodiles survived the KT extinction unharmed • Three families survived the Campanian, the Maastrichtian and the Tertiary • Crocodile lineage has undergone little change since the time of the dinosaurs • Crocodiles that are present today appeared in the Creataceous (http://en.wikipedia.org/wiki/Crocodile)

8. Crocodiles take refuge in caves and tunnels which usually open beneath the surface of the waters in which they live • They can also move very fast in certain instances such as to capture food • The reptiles invented the eggshell, which keeps the egg from drying out and allowing for reproduction to take place away from water (or, at least, from extremely moist environments) (www.biol.paisley.ac.uk)

9. All large crocodiles have powerful claws They have limited lateral movement in their neck These animals are cold-blooded predators and therefore can survive long periods without food and therefore don’t go hunting as often as other predators They are ambush hunters Crocodiles eat fish, birds, mammals and sometimes even other smaller species of crocodile The earth’s largest reptile is the Saltwater crocodile

10. The skin of the crocodiles is armoured Scutes on the back and tail of these reptiles are reinforced by underlying osteoderms The teeth are sharp and conical in shape Only two sacral vertebrae are present and a well-developed system of abdominal ribs are present Their hind legs are longer than their forelegs Modifications of the respiratory tract show the relationship to the amphibious lifestyle Crocodilian heart has a patition between the thoracic and abdominal cavities like the mammalian diaphragm

11. Conclusions • Because crocodiles lived in tropical fresh waters which well supplied with fish, they were able to avoid being preyed upon by other archosaurians at the beginning of the Tertiary. • Crocodiles also have various body adaptations which enable them to maintain a better standard of living when compared to the other animals. http://en.wikipedia.org/wiki/Crocodile