Were there "fish dinosaurs"?

Our 5-y/o got into a discussion today at school with some other kids about whether or not there were "fish dinosaurs". My kiddo's point was that plesiosaurs were reptiles, but not truly dinosaurs or fish, as were ichthyosaurs (yes, this is all him ... he loves dinosaurs). There were ancient fish as well, but no dinosaurs were fish. Most everybody in his class disagreed, and his teacher asked my kiddo to bring in some research. I'd like to help him find a source, even if it's too advanced for his stage, which I can help him "translate" into 5y/o language ... can anybody help us out?

Not really a great research site but good old wikipedia (please click) also clearly states that the Plesiosaur falls under "reptilia"

The Dinosauria were originally classified under the class "Reptilia," but what made the significant difference between Dinosaurs and other reptiles were the design of the pelvic girdle, allowing their legs to be straight below their bodies. When dinosaur classification/taxonomy is used, dinosaurs are classified as land dwelling "reptiles." (Though theropod dinosaurs are more closely related to birds.)

The "Dinosaur fish" those kids are referring to are marine reptiles and not Dinosaurs. They don't share the same lineage like crocodilians don't share the same lineage either (this is a common misconception). Dinosaurs come from the line of Archosauria (a group that includes Postosuchus), while Plesiosaurs, icthyosaurs, and pliosaurs do not...although, taxonmically they could be if you said they were. However for that to be effective you'd have to reclassify all genera of marine reptiles and dinosaurs to see what made a dinosaur a dinosaur.

Hope this helps...

Raptor Lewis wrote:

The Dinosauria were originally classified under the class "Reptilia," but what made the significant difference between Dinosaurs and other reptiles were the design of the pelvic girdle, allowing their legs to be straight below their bodies. When dinosaur classification/taxonomy is used, dinosaurs are classified as land dwelling "reptiles." (Though theropod dinosaurs are more closely related to birds.)

The "Dinosaur fish" those kids are referring to are marine reptiles and not Dinosaurs. They don't share the same lineage like crocodilians don't share the same lineage either (this is a common misconception). Dinosaurs come from the line of Archosauria (a group that includes Postosuchus), while Plesiosaurs, icthyosaurs, and pliosaurs do not...although, taxonmically they could be if you said they were. However for that to be effective you'd have to reclassify all genera of marine reptiles and dinosaurs to see what made a dinosaur a dinosaur.

Hope this helps...;)

Sorry that was me. I forgot to log on before posting that.

With the guests postings being abled now it indeed is confusing sometimes.

Read the information with interest. I hope Emi will log back in soon and let us know what she thinks of it

Indeed it is, Copper. And thanks.

Do you think I explained it well enough?

Some dinosaurs may have spent at least a little of their time in the water (it has been proven that Baryonyx and Spinosaurus were fish eaters). However, no dinosaur whatsoever lived full-time in the oceans. The study of life in the prehistoric oceans is paleoichthyology (correct me if I'm wrong). It is different from the study of dinosaurs, but both the study of dinosaurs and ancient sea life are branches of paleontology. So, tell your five-year-old that ancient sea life and dinosaurs are two totally different things. Because they were both reptiles, they could be considered prehistoric "cousins." But they couldn't be considered the same thing.

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