But it has create two "missing links" on either side of it. "missing links" are increasing twice as fast as they are discovered. Take that, Darwin!
Paleontologists tell us that most ancient species survived no more than a few million years, then died out, to be replaced by others better adapted to the changing environments.
They also say that every species is related to every other, more or less closely.
So, what's been found to date in the fossil record is a VERY small sampling of all the species which ever existed.
And, common features allow them all to be traced back to their common ancestors.
But the number of transitional forms varies from species to species, depending on the luck of what's been so far discovered.
These things are not so very hard to understand, imho.