When a fossil is generated in the soul sand valley biome, some of them get duplicated above.
Seed: 2971383780711649635 Coordinates: /execute in minecraft:the_nether run tp @s -38.73 42.60 -45.54 -112.15 16.41
MC-171101 strange fossil generation in the nether
MC-171312 Skeletonstrukture-World-Generator-Bug
MC-171632 Bone Structure Tower
MC-171024 Fossils in the nether can spawn inside of nether fortresses and bastion remnants
MC-170897 Nether fossils can generate floating if a cave carver removes the ground beneath them