Welcome to another round of Mystery Dissection; no frills or miracles-required this time; tell me what you can about this specimen.
Difficulty: No-way-you-can-get-this-down-to-genus-level; blurry photo; scale unknown
Stomach-Churning Rating: 5 at worst, especially once you realize it’s in preservative; hence the odd colour.
What's In John's Freezer? 
Looks like a frog leg.
That looks like Fred, the lab assistant who locked himself in the freezer last summer.
I vote cat forelimb
My guess is frog leg. Staple of high school dissection labs everywhere.
Medial aspect of left frog leg with gracilis major and plantaris removed to show semimembranosus and semitendinosus and all 3 tibialis muscles. Rana or Xenopus?
Good guesses one and all, but hypnotosov got it right!
Just kidding. Fred is doing just fine.
I can totally see where the frog leg answers are coming from, and I didn’t anticipate that one; for some reason I expected someone to squint and see it as an avian forelimb (elbow+wrist). Which it is not, of course.
It is the hindlimb of a juvenile basilisk lizard (“Jesus Christ lizard”); Basiliscus vittatus. The stout tendon-bearing muscle near the top/left of the image is M. iliofibularis (the other, bigger, sheetlike muscle above it is almost certainly M. puboischiotibialis), and the tail is barely visible at the bottom of the screen. The ankle is angled off on the far right side. To my mind (and from a quick skim of the literature), frogs don’t seem to have such a stout/strongly tendinous M. iliofibularis but I could be wrong there, and there are a lot of different anurans.
OK enough difficult mystery limb pics for now. I’ll have some time soon to cut up some new critters and boost the diversity of images in Mystery Dissection, so stay tuned!