The funny thing, though, is how those extinct animals when we find them continue to further outline what looks like a phylogenetic tree of life, as evolution demands. That's important because an intelligent designer wouldn't have to mimic evolution so precisely.
For instance, we could someday find a bird-amphibian hybrid or a fossil thereof, if only an intelligent designer had ever once seen fit to order one. Such a monster could not have evolved under the commonly understood amphibians-reptiles-birds evolutionary scenario. In fact, it would falsify that scenario at once. However, 145 years after Darwin, we have seen nothing like that. What we see might as well be evolution as anything looser.
The presence of evolution doesn't preclude design, nor would the existence of a Designer preclude evolution.
When one already has a bias toward a 'tree of life' theory, one tends to make successive finds fit that paradigm.