Is it possible that there could be marine dinosaurs in the depths of the ocean as only the land ones died?

Question

Examples:

http://en.wikipedia.org/wiki/Ichthyosaurs
http://en.wikipedia.org/wiki/Plesiosauria

Answer 1

There were no marine dinosaurs. The marine reptiles, such as ichthyosaurs, plesiosaurs and mosasaurs that lived in the same time period as the dinosaurs were not technically dinosaurs themselves.

As to an ancient marine reptile surviving hidden in the depths somewhere, it is exceedinly unlikely.

While critters like the coelacanth may have been unknown to science, they weren't unknown to the fishermen of the regions they live in, those fishermen just didn't recognize the zoological significance of this big, smelly, oily, not very tasty fish. The recent discovery of coelacanth in Indonesia actually occurred because a Canadian grad student noticed one for sale in the fish market.

Something like a plesiosaur, or ichthyosaur, would definitely be noticed by local fishermen, and we simply don't have anything more definite than vague 'sea serpent' stories as eyewitness accounts.

In addition, critters like coelacanth and collosal squid remain mysteries to science because they live deep, deep in the ocean and never come to the surface. Marine reptiles would still need to breathe air, and would be seen at the surface fairly regularily, much like whales, sea snakes and sea turtles today.

Plus, there is absolutely no fossil evidence from the entire Cenozoic period indicating that any of these marine reptiles survived. Plenty of fossils throughout the Mesozoic, but not a single one since. That is some pretty good evidence that they don't exist any more.

Answer 2

Not dinosaurs. Some marine reptiles gave live birth but were not dinosaurs.

Anyway all dinosaurs and reptiles had to breathe air so were not nor could they ever be truly deep ocean creatures. They would be restricted to the upper levels of the ocean except perhaps for the dive to feed or such like the sperm whale (even these do not go to the bottom). It would be very unlikely that a population would remain unseen this long, without even there remains washing ashore somewhere.

Answer 3

Could the sea monster stories be written off as sightings of other marine creatures? Is there any possibility that the "sea monster" stories could be sightings of a few remaining individual marine reptiles from an earlier age?

Answer 4

That would be nice. But no, I don't think so Dinosaurs have to
breathe so they'll have to come up for air.
If there were any we should have spotted them by now.
There are still some very creepy fish down there though.

Answer 5

more than possible there was a prehistoric shark caught last week it looked real weird like a giant piranha ,and there are several species of prehistoric fish in the depths regularly caught of the coast of zanzibar ,
also the nautilus (shell fish) is prehistoric and they say the great white shark is as well

Answer 6

Possibly as there are some depths that we have not yet expored and will not be able to until the technology allows us to sink down to that level of pressure.

Answer 7

Highly unlikely...

No sightings, no bones, no evidence. Even marine dinosaurs had to lay their eggs on land (like modern day marine turtles). Eggs cannot hatch under water.

Answer 8

Perhaps. Every day they still discover new species in the ocean. Why not?

Answer 9

Could be possible, I suppose?

That's why some people believe in the loch ness monster.

Answer 10

Exactly what is a marine dinosaur?