Sorry, but every fossil, every individual without exception is "transitory" between its ancestors and descendants.
You, bray, are "transitory" -- because of a small number of mostly harmless mutations, you are individually unlike your parents, or your children, if any.
The average number of DNA mutations per individual is on the order of dozens, perhaps 100 per generation.
Multiply those times a million generations, and you accumulate enough changes that separated populations can no longer interbreed.
And that, by definition, is called "speciation".
Of course, fossils alone can't tell which species were "parents," and which "child".
But DNA analysis tells a lot about how closely related today's species are, and when their common ancestors lived.