It's not a Targ. The targ was invented afterwards and looks nothing like this animal, nor it has any reason to.
We had this debate on the TrekBBS a few years ago. The animal featured in ST III was a Klingon canine with reptilian qualities. The production crew called it Fifi Rebozo. The novelization called it Warrigal (ie. after the Australian dingo, a native dog).
When they had a child playing one in the Universal Studios "A Star Trek Adventure", they credited it as a "puppy lizard".
The script of ST VI described those white doglike creatures on Rura Penthe as "jackal mastifs".
The first targ
featured in Trek was in early TNG, when a real boar was dressed up in latex appliance spikes.