But there is no way for you to know that those are really “missing links”.
These are assumptions based on similarities in morphology. Nobody was there to observe or measure.
As has been shown elsewhere in this thread, morphology is not a very reliable indicator of speciation. If so, then, in the presence of only their fossilized remains, the Retriever could be mistaken as an intermediary between the Chiuaua and the Great Dane.
You would make a good trial lawyer. I can hear you now at the OJ trial. “If you weren’t there, you must acquit.” Brilliant. Why hasn’t anyone else thought of this?