Todd, definately not a black panther (dark melanistic phase of cougar) or black jag (dark melanistic phase of jaguar). Even immatures of both are 80-100lbs. Both have been documented in South Texas, but not for many years. However, your cat has a higher rump and longer tail than typical feral domestics...very interesting. Hair on your cat is too long to be a dark phase of any regional wild cat; maybe a hybrid? I would live trap him using sardines and take a closer look.
