Many reptile species died during the K-T event, but snakes, lizards and the crocodilians persevered. Crocodilians have been on the planet for about 240 million years. There are 23 crocodilian species today, including alligators, crocodiles and caimans. Mesozoic crocodilians were generally larger than living species. Another prehistoric order of reptiles is the sphenodontians. Today, there is one living sphenodontian -- the tuatara, which lives in New Zealand.
The tuatara (Sphenodon punctatus) is the only surviving species of an order that flourished 200 million years ago in New Zealand. Konrad Wothe/Minden Pictures/Getty Images
A zookeeper cradles rare twin platypus babies. The platypus is one of the few remaining monotremes on Earth. Jason Edwards/National Geographic/Getty Images