There are DEFINITELY black panthers / melanistic jaguars / melanistic leopards in Missouri. I've seen one.
It was in 2017 around the Thanksgiving holiday. We were driving in our truck on our rural grazing property during the 12:00P to 1:00P, during the sunny day. A GIANT black panther or jaguar came into our view from the north to our left as we were driving east and was running south across the field in front of us at full speed. The cat was about 30-40 yards in front of our truck and we got a good look at it fairly close up for several seconds. The cat appeared to be more dark charcoal gray as opposed to deep dark true black. It was running very low to the ground and the back legs were overtaking the front legs much like a cheetah looks when running after a gazelle. The panther speed was astonishing to us. The head was absolutely a jaguar type rectangular box skull and the tail was long and extremely thick with a curl at the end. It was a giant animal, seemed full grown, healthy weight and was very thick.
There were three other relatives with me that can corroborate the sighting and we all agree it was a black jaguar or leopard. We were pretty rattled and drove up the house, not believing what we had just seen. A few hours later we investigated the implement barn where we saw it run behind and installed a game camera to see if we could get it on camera.
The property is situated on the county line between Bates County and Vernon County. The closest towns are Rich Hill, MO, Hume, MO and Metz, MO.