I don't think there is. For one, like any other forms of organisms, they, too, must have undergone evolution, which may cause changes into their form.
Another thing is that, there have been explorations to get a view of how the bottom of the deepest trenches look like, and to see whether animals can still survive.
If I am not mistaken, this has led to the discovery of hydrothermal vents, which allow chemosynthesis to take place that in turn provides for the food needed by marine animals to survive. So yes, there are animals living deep down the ocean, with total absence of light but not the Jurassic kind. They are rather big and small fishes, whose appearances are far from what we have always observed, mainly due to the various adaptations that they have undergone.
If you have another ideas or readings you may want to point us to, I would love to read them and converse with you further about this.