According to evolutionary theory, there are only gradual, slow, transitions from one species to another. They never blend together. But prof, in the strata and in nature today we only find gaps between all the species. These gaps are never filled. We only know what earlier species looked like because of the fossil record.
Evolution always goes from smaller animals to larger ones.
That's an important proof of evolution. Because evolution occurred gradually and slowly, each strata in the geologic column contains its own distinct fossils. For millions of years, ancient plants and animals died and changed into fossils. That is where all the fossils came from. No fossils before the Cambrian have been found because soft body tissues are never found in fossil form.