Some creatures only appear once, never to be found again, accidents of light and angle and fate. This is one such:
It took me a day or two to see the elephant and the sharp-goateed tiger:
and not until today did I discover (1) the muppet Statler on the left side:
I don’t think I could find that rock again, and even if I did, I doubt that those creatures would manifest again.
Other readings are of course possible. The ‘musk ox’ could be a disgruntled chimpanzee, and the ‘elephant’ may be an open-jawed creature about to bite Statler’s head off as the tiger looks on. YMMV.