Dominant theory is that 'normal' dinosaurs went extinct from ether super volcano or meteor impact or combination of both. However there were aquatic dinosaurs that are not present at this day. Was it one of the events above that caused them to go extinct, or was it something else?

How did aquatic dinosaurs go extinct?

  • There is a very good answere here, which lists the reasons and the species that you asked about. reddit.com/r/askscience/comments/1nyuqs/… Mososaurs and pliosaurs were technically giant reptiles, 10 meters long. Alligators and Tortoises are marine and they were the only surviving sea-reptiles. the KT extinction killed many tropical corals and ecosystems according to fossil records. – com.prehensible Oct 23 '17 at 7:05
up vote 5 down vote accepted

Spinosaurs (like Spinosaurus) are currently only known from 112-97 million years ago, although isolated teeth push the origin possibly back to ~150 Mya. At least now, there isn't any definite spinosaur material younger than 97 Mya.

So spinosaurs were already extinct when the rest of the non-bird dinosaurs went extinct at the end of the Cretaceous, whether by meteor impact, volcanism, a combination, or something else completely.

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    keep in mind spinosaurus is also nowhere near fully aquatic. – John Feb 12 '17 at 15:55
  • Spinosaurs and ichtiosaurs dissapeared before a great anoxic event at 90Ma. What about pliosaurs, they are reptiles strictly speaking, 10 12 meters long, fully marine, that vanished at the KT boundary. en.wikipedia.org/wiki/Plesiosauria and mososaurs. – com.prehensible Oct 23 '17 at 7:15

Not a lot of people realize how extreme and how sudden the dinosaur's extinction was. Radiolab did an episode with several geologists about the extinction of the dinosaurs. Basically, when the meteor hit the Earth, a humongous amount of material was ejected into space, and most of it fell back down to the surface all around the planet. As it fell it left an incredible amount of heat in the air, raising temperatures to as high as 1200 Farenheit (650 Celsius). Anything too large to hide under dirt died (dirt is a surprisingly good insulator). Even plankton and animals near the surface of the ocean would have been decimated by the heat, destroying the food chain that supported the large mesosaurs and plesiosaurs. The whole process is thought to have taken 2 hours. The fact that anything lived through that at all is dumb luck, and even if a semi-aquatic dinosaur was deep enough to avoid the worst of the heat, the food supply would have been destroyed and they would have starved shortly after the impact.

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    Interesting info, but the aquatic dinosaurs went extinct millions of years before the meteor. So, this doesn't answer the question. – rumtscho Oct 25 '14 at 11:12
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    @rumtscho Mosasaurs didn't go extinct until the end of the cretaceous. Some plesiosaurs did too. While these are technically not dinosaurs, for all practical purposes they are close enough, and a lot more aquatic than spinosaurus ever was. – user137 Oct 25 '14 at 14:06
  • now that I read the question again, I may have misunderstood it. I have to make a pro forma edit before I can remove the downvote. But I have to wait for the peer review. – rumtscho Oct 25 '14 at 15:43

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