Aquatic dinosaurs

[Maia <dalmiro@mesopy.obspm.fr>]

I've seen often stated, I think even in this mailing list, that there
were no aquatic dinos, yet some exist even today (penguins). To what
time can we trace the first "aquatic dinos"? are they in anyway related
to ichtyosaur extinction or loss of diversity? Why do people generally 
fail to recognize the existence of aquatic dinosaurs? I've just found
such a claim in one post at sci.antropology.paleo

As an aside, is there any online abstract service in paleontology?(like
the nasa abstract service in astrophysics were you can search abstracts
by authors, date or content and even retrieve full articles.)

Dalmiro Maia