A prehistoric visitor in Treasure Reef.

This was originally drawn when the Season of Abyss first came out.

Uncolored version, cause that one also looks nice:

Mosasaurus. Animal Ghosts. Edited by Claudia Clow. Illustrated by Walt Disney Productions. 1971.

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A lone pleurosaurus basks near the water surface before returning to the shallows to hunt small fish.

Potentially dumb question but how do Ichthyosaurs and Pliosaurs fit into everything? Are they more closely related to crocodiles or birds?

And (I'm hesitant to ask this but) are they technically fish in the same way all mammals and thus whales could be argued to be technically fish? (If I've now accidentally made this ask cursed, feel free to delete).

So we don't know where Ichthyosaurs or Plesiosaurs (which includes Pliosaurs) go, exactly, but they aren't more closely related to crocs or birds! They might be close to turtles, or not close to any living reptile group at all. They're an enigma

Mosasaurs, however, are straight up lizards. Like actual giant lizards. We don't know whether they're closer to snakes or monitor lizards, but they're lizards

And yup, aaaaaall of them are fish

Platypterygius australis

Splashy girl bleps until the sun goes down.

Yeah I know this poll is a little apex predator heavy, but to be frank, most sea creatures (living and extinct) would amount to nothing more than fish/whale/ichthyosaur/shark, etc. fodder and that would not make for a fun poll.

Just added another super cool fossil to the collection! This genuine Plesiosaur tooth was found in Morocco and dates all the way back to the Cretaceous period. It’s also quite a large specimen, measuring almost 2.5” in length!

Plesiosaurs are often mistaken for dinosaurs, however these prehistoric creatures are actually part of a separate group known as "marine reptiles." They first evolved in the Triassic (208.5 MYA) and thrived until the massive KT extinction event caused by the Chicxulub asteroid. This took place at the end of the Cretaceous, and was the same extinction event that wiped out the non-avian dinosaurs (66 MYA). 💥🌊

Plesiosaur by the paleontology books

[ Part of the excavation process of the 83-million-year-old mosasaur. ]

"Researchers in southern Manitoba have made the rare discovery of what may be a complete fossilized skeleton belonging to a roughly 83-million-year-old marine reptile. Excavations are still ongoing, but scientists have uncovered roughly 75 per cent of a mosasaur skeleton near the small community of Miami, Man., about 110 kilometres southwest of Winnipeg. Finding such an intact skeleton is rare, according to Adolfo Cuetara, the executive director of the Canadian Fossil Discovery Centre in Morden, about 20 kilometres southeast of Miami. "Normally you're only finding isolated bones, but this time it looks like we have a whole skeleton," he said in an interview with Radio-Canada on Monday. In early July, a technician with the centre found a small bone while digging with a tractor on a plot of land that used to be a bentonite mine, and which the Morden organization purchased in 2004. Finding small bones isn't unusual, Cuetara said, but using hand tools, that technician soon realized that the bone was not an isolated discovery. Over the next several days, the team found 15 vertebrae, all from the same marine reptile, Cuetara said."

Read more: "Marine reptile skeleton dating back to age of dinosaurs discovered in southern Manitoba" from CBC News.

Jurassic June day 13.

Tylosaurus.

Commission.

"The marked similarity between the shape of the body of the Shark (above), the Ichthyosaur (centre), and Dolphin (below) does not mean that they are all related, but is only the outcome of complete adaptation to the environment, with the same mode of life (convergence)."

Prehistoric Sea Monsters. Written by Dr. Josef Augusta. Illustrated by Zdeněk Burian. 1966.

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An injured eromangasaurus has attracted the attention of a large kronosaurus lurking below. 

I recognize that many would have me add other groups, but I'm specifically doing the "air/land/water" trio that many people think were the only animals alive in the Mesozoic. You know. For fun.

There's something in the water.

Made a fan-made vivosaur out of boredom and inspiration!

Say hello to Ichthys, the Air-elemental vivosaur! (Not named Ichthyo because Dean/ZestyZino already nabbed the name for an Ichthyovenator.)

Why the choice of the Air element and lightning theming? Because of Mary Anning and the fact that she survived a lightning strike as a baby. (Also, thank you FGO's Mary Anning for inspiration as well.)

Oh yeah, the seashells also connect to Mary Anning, cause iiuc "She sells seashells on the seashore" tongue-twist is in reference to her.

And, it's kinda hard to see in the alt colours, but I designed Ichthys' eyes after the olden interpretation of Ichthyosaurus with the whole "bones in the eyes"-thing.