When did dinosaurs first exist? When did birds first exist? What about the teradactyl?

I was reading an article that said "birds are the modern versions of dinosaurs." I was wondering if the birds we see today existed when dinosaurs roamed the Earth. Did fish exist then too? Also, how did dinosaurs become extinct. When the event (of their extinction) occured, reptiles such as alligators and turtles survived, right? I'm not sure.. Also, if those sea animals survived, why couldn't the teradactyl survive? It has wings and since I read that "birds are modern day dinosaurs" ..why couldn't they survive too along with other species with wings? Also, were there any dinosaurs that lived in water at the time when dinosaurs lived? This is the article I read: a href="http://news.yahoo.com/s/livescience/20090604/sc_livescience/dodinosaursstillexist"http://news.yahoo.com/s/livescience/2009…/a THANKS =)