In South San Antonio, Texas, a weird unidentified creature was spotted in the 19th Century. It bore some resemblance to a dog, but was endowed with wings. It flew onto the roof of a house on Poteet Highway. Police, summoned to the scene, shot at it, but apparently to no avail. It scampered off into the woods.
Isolated creatures like this, of which no other specimen is reported, make one think in terms of portals from other universes, where such creatures might proliferate.