Researcher: Dinosaur fossils come in various forms, including mineralized bones and tracks in dried mud flats.
Conclusion
It's not surprising that we usually don't find mineralized dinosaur bones and dinosaur mud tracks in the same area.
Evidence
Creatures that scavenged dinosaur carcasses most likely went to mud flats to find food.
Evaluate
This is one of those arguments that is super hard to understand on a first (or second) read, but if we can figure out the author's intended meaning, then we're actually 90% of the way to our correct answer.
There are two types of dinosaur fossils, but we don't find them in the same place usually. We either find bones or find footprints in the mud.
The author has a theory for why we don't find them together, and since our author is trying to explain a puzzling phenomenon, we can use our Curious Fact / Explanation mindset:
Curious Fact ... why don't we find bones and mud tracks in the same place? Author's Explanation ... animals that would scavenge dinosaur carcasses frequented mud flats to find food.
Again, what?! We need to make sense of causal story the author is telling here. It might help to think about what it would be like if we did find dinosaur bones and mud tracks in the same place:
It would mean that a dinosaur died in the mud flat. We're generally finding dinosaur bones at the spot where they died (they're too heavy and not-useful for animals to have moved them, so other than weather events like a hurricane or earthquake moving them, they will be found where the dinosaur died).
So if a dinosaur died in a mud flat, it would definitely leave some footprints in the mud en route to its death scene, right? How come we don't see those final footprints in the mud?
The author is saying that there were scavenger animals who roamed mud flats looking for food. If they happened upon a dead dinosaur, then they would go to town on its carcass.
So the author is either thinking that we don't find bones in the mud flats because there were scavengers roaming the mud flats who would perform "clean up duty" and eat the bones.
Or ... the author is thinking that we don't find muddy dinosaur footprints near the dinosaurs bones, because the footprints of the scavengers that were eating the dinosaurs carcass messed up the dinosaurs mud footprint (kind of like if someone walks through snow, they leave footprints, but if you walk through their footprints, you can't clearly see that person's boot print anymore).
Goal
Since this is Strengthen, we are most likely adding plausibility to the author's story (i.e. scavengers in the mud flats would have consumed the dinosaur's bones or obscured the dinosaur's footprints), or we might be ruling out an alternate explanation for why bones and mud prints aren't found in the same place.