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There were no purely aquatic dinosaurs. It is generally assumed that all dinosaurs were terrestrial but there may have been semi aquatic dinosaurs that spent some time in water and some time on land.
The marine reptiles generally assumed to be dinosaurs were in fact only distantly related.
The sauria clade of reptiles would evolve into 4 main orders of reptile. Ichthyosauria, Sauroterygia, Lepidosauromorpha and Archosauromorpha.
The Archosauromorpha order of reptiles evolved from sauria about 260 million years ago in the late permian period. They would later evolve into crocodiles, dinosaurs/birds and pterasaurs. Dinosaurs did not evolve until the late Triassic period about 230 million years ago. All dinosaurs apart from avian dinosaurs became extinct 65.5 million years ago. The only "dinosaurs" alive today are the birds.
The Ichthyoaurs were the 1st class of reptiles to adapt to an aquatic lifestyle. Ichthyosaurias evolved from sauria about 245 million years ago. They could be found in the ocean for the next 155 million years. They became extinct 90 million years ago about 15 million years before the non avian dinosaurs.
The Sauroterygia were thought to evolved from sauria about 245 million years ago. They were mostly semi aquatic reptiles all but the pleisoaurs became extinct during the extinction event at the end of the Triassic period. The pleisosaurs are thought to be mainly aquatic but died out 65.5 million years ago during the K-T extinction event. The largest known carnivour was a pleisosaur, Lipleurodon.
The Lepidosauromporpha were thought to have evolved from saurai again 240 million years ago. They are very closely related to sauroterygiae. They would go on to evolve into many of the modern day reptiles such as lizards, snakes & turtles. One family that evolved from this order of reptiles was the mosasaurs. Mosasaurs did not evolve until the early Cretaceous Period about 140 million years ago and were to become extinct at the end of the Cretaceous along with non-avian dinosaurs, pterasaurs and pleisosaurs.
Just a sub note that if you really want to see an aquatic dinosaur then go to the zoo and watch the penguins. Birds are so closely related to dinosaurs and share such similar morphology that they are now generally considered as avian dinosaurs.
What else can I help you with?
What is a sentence with the word extinct?
Why did the dinosaurs go extinct? Humans will never go extinct!
A sentence with word extinct?
Dinosaurs are now extinct. There are many species of birds that are extinct.
Are carnivorous dinosaurs instinct?
Extinct. Yes, ALL dinosaurs are extinct.
Why do scientist think the dinosaurs went extinct?
One reason is that there were a lot of fossils in many layers of rock and then suddenly, there are a lot fewer. Also, there don't appear to be many dinosaurs alive today. So, they went extinct. Do you really mean "how" did the dinosaurs go extinct?
Did the ocean dinosaurs go extinct at the same time as the land dinosaurs?
no around 1million years later most of them died out
What dinosaurs do they have?
Nobody has dinosaurs; they're extinct.
Where was the place that the meteor stuck the earth that caused the dinosaurs to go extinct?
mexaco
How did dinosaurs go extinct(theory)?
It is a rock called an asteroid, or comet, or a volcanic eruption.
Why do you think the dinosaurs became extinct?
because have you seen any dinosaurs around? and go dig everywhere you will eventuly find dinosaur bones.
What will effect a penguins habitat?
Dinosaurs love to eat penguins. In the unfortunate event of the resurrection of dinosaurs, penguins will most likely go extinct.
When did the dinosaur's become extinct?
Non avian dinosaurs became extinct 65.5 million years ago, at the end of the Cretaceous. However, birds are considered dinosaurs. Because birds still exist, dinosaurs are not completely extinct.
Are dinosaurs extnit?
No, but they are EXTINCT
