Fossils like the ones you describe do exist. Their existence is explained by periods of time in our earth's history when the continents were connected. The most recent of these "supercontinents" is called Pangaea. Pangaea existed about 300 million years ago. The evidence of Pangaea's existence include both fossil records and geological evidence of the earth's tectonic plates as well as mountain formations, land shapes, etc.

So, to answer your question, it's not that the animals that made the fossils traveled long distances and colonized distant lands. Rather, at the time that the animals lived, the lands were much closer together or even connected. It wasn't until after the species' extinction that the land holding the fossils separated.

Well, fossils cannot really move, they are imprisoned in rock. However, millions of years ago, all of the present continents were located as ONE GIANT CONTINENT. If there were animals and plants living on this ancient land mass, and these organisms became fossilized, then in the millions of years since then, when the continents split up and drifted apart, then fossils could become separated.

Since fossils aren't living, it's not possible for them to move anywhere--except to perhaps roll downhill, or to drift along with whatever continent they happen to be attached to. It's this last point that I think you're trying to get at.

There are many examples of similar fossils on landmasses that are far apart today. For example, there are nearly indistinguishable mesosaur (freshwater reptiles) known from eastern South America and western Africa. At the time mesosaurs lived, however, South America and Africa were connected and these animals lived (and died) across this continuous landmass. Some mesosaurs were lucky enough to become preserved as fossils. As Africa and South America slowly drifted apart, the mesosaur fossils also became ever more separated. This process didn't happen overnight, rather it took hundreds of millions of years.

This is actually one of the proofs of continental drift! Millions of years ago, all of the continents were bunched together as one continent, called, Pangea. The continents move very very slowly, only a couple inches per year. When they separated, fossils stayed on each continent where the animals originally died. Now, there are fossils in multiple places all over the world that used to be next to each other but have since drifted away. Here's an image to help show it:

Yes - in fact, the oldest fossils of Eucalyptus are found in South America, but the tree is now native only to Australia. Apparently, South America and Australia were connected (probably via Antarctica) between 50 and 30 million years ago, allowing plants and animals to move between the two continents.

Let's start off with how fossils are created. When a living organism such as a plant or animal dies, and its body is preserved in rocks, it forms a fossil. So we can only find fossils of an organism in the areas where it lived. The continents that we recognize today weren't always shaped and located where they are today -- they're always moving at a very, very slow rate (millimeters/year), due to plate tectonics. So millions of years ago, Australia and South America weren't in the same spots on the globe as they are today. There could have been some organism that lived in an environment that existed on both South America and Australia, but that it didn't live on the other continents. So yes, it is possible for it to only be found on those 2 continents.

Good question! Over a hundred years ago, scientists identified similar fossils on continents that are now separated by large oceans (like Australia and South America). This led to the discovery that separate continents were once connected in the geologic past, but we lacked a good explanation of how the continents collided and separated until the theory of plate tectonics, which is only about 50 years old.

Many of the fossils found on the South American and Australian continents are of plants and animals that could not realistically swim across a large ocean (see the attached figure),
figure
therefore the best explanation for the wide distribution of fossils is that continents were once connected. The figure above that I attached (from the US Geological Survey) shows the "supercontinent" Gondwana, which began to form about 600 million years ago and started to break up about 200 million years ago. We think that South American and Australia were "attached" at this time and that animals and plants could have spread across these continents.