Panther

Panthers were a type of felid mammal.

In 1960s New York City, a panther was liberated from a zoo by a mad scientist, who took control of it. He ordered the panther to kill the Second Doctor, but he used a bottle of acid to drive it off. (TVC: The Monsters from the Past)

In 1970s London, the Third Doctor and the Brigadier encountered a panther at a zoo. Normally fierce, this panther was as docile as an ordinary house cat. This odd behaviour made the Doctor and UNIT suspicious of nearby activities. (TVC: The Arkwood Experiments)

Circa 1992, a was sighted in Derbyshire. (NA: Cat's Cradle: Witch Mark)

On Christmas Eve 1941, the Eleventh Doctor claimed there were panthers on an upstairs floor of Uncle Digby's house. (DW: The Doctor, the Widow and the Wardrobe)

Behind the scenes
As far as the DWU is concerned, panthers have been portrayed as a unique species. In reality, though, "panther" is a term derived from the Latin genus name,. Various cats — but principally the leopard, cougar, and jaguar — are therefore rightfully called "panthers", with different geographic regions applying the label to different cats. The text of neither The Monsters from the Past nor The Arkwood Experiments help us understand precisely what the Doctor encountered. However, as drawn, both "panthers" appear to be s. Again, though, a "black panther" isn't technically its own species, but merely a type of leopard, jaguar or cougar with a particular pigmentation.