Yes! Other commenters are talking about shallow sea fossils. Shallow sea fossils are very common, probably the most common fossils out there. But fossils of deep sea animals are pretty rare.

This is for two reasons. First, the ocean floor is constantly getting subducted beneath the continents, destroying any fossils that it contains. This especially true for extreme deep sea trenches like the Mariana Trench, which are connected directly to subduction zones. Second, the pressure in the deep sea is not conducive to preserving mineral remains. Most fossils are made of calcite or apatite, and both degrade under pressure.

However, we have found some deep sea animal fossils! Like these sea stars found in the alps, or this ichthyosaur that probably filled a similar niche as sperm whales.

As others have indicated, yes, fossils of deep sea organisms tend to be more rare, or at least are not as well represented as fossils in shallow marine or continental slope areas. The primary reasons for this is subduction of oceanic lithosphere and the general depositional history that characterizes these environments (e.g., Holland, 2016). As highlighted in this paper (and generally in many paleontology textbooks), the fossil record is relatively biased toward organisms that were deposited in environments that have a higher preservation potential (of which the deep sea, along with extremely erosive environments etc., is not one). An additional influence, depending on the geologic period and the type of fossil in question, that can influence preservation of deep sea fossils is the carbonate compensation depth, i.e., basically the depth below which carbonate begins to preferentially dissolve (there is a similar depth for aragonite). Given that the preserved part of many marine invertebrates are their calcite or aragonite hard parts, areas of the sea floor below the CCD are not conducive to preservation of their remains.

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Not necessarily. Ithaca NY is famous for its waterfall gorges, which always have a TON of fossilized ammonite and stuff. There are places that advertise to tourists that way. Just depends on local geography and tide currents etc

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You'd have to define deep I suppose. I think it probably IS fair to say that most fossil seabeds were not from what we'd call the Hadal zone nowadays.

Hmm. Actually, they have a pretty good idea of which plates were where at different epochs and I'm not sure there IS an exposed rock face that would have been Hadal, and I'm not sure that geologic processes are particularly likely to result in present trench communities to fossilize and then be exposed some time in the future. My general impression of most of the truly deep sites is that they're rifts at the bottom of subduction zones and rock that ends up sinking below a plate isn't coming out looking like it did when it went in. I THINK. I study evolution but not paleontology or geology. If someone does know of one I'd love to read about it!

You might find this interesting:

https://www.jstor.org/stable/20144263

That's a paper on a fossil anglerfish. Not all anglerfish live in the deepest parts of the ocean, but apparently they think the formation that one is from represents mostly fish from around 1000m. It certainly gets deeper than that but a lot of what you'd see living there would be "weird" compares to the fish most people are familiar with.

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Deep sea floors are constantly changing through subduction zones, so a not insignificant quantity of the fossilised remains will get pulled back to the upper mantle and destroyed.

Past this, one of the main ways that fossils are preserved in shallow seas are where an event occurs causing a large silt deposit on top of the dead animal, causing it to effectively be entombed in mineral deposits, which eventually leech into and replace the animals prior body structures. The faster the animal is entombed, the better preserved it will be. See the fossil that was excavated in a Canadian mine where a dinosaur with almost intact skin and innards was found. In fact the innards had not even hardened which led to the fossil breaking during excavation.

Another issue is that a lot of deep sea life is either cartilaginous or does not involve some sort of hard carapace. Bones and exoskeletons preserve better, and whilst fossil jellyfish have been found, if you weren't an expert you would think it was a smear on a rock

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Not really . Location location location. Most fossil rich real-estate was deep sea at some point in time. The world turned upside down a few times over. When it comes to numbers, deep sea critters are among the most found.

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