You know the drill- tell me what you can about this rather messy dissected specimen from The Freezers. What are the structures shown? Identification to genus/species level is probably not possible, but try to pin down the group of organisms it is from as tightly as you can:
Edit: This post had a Stomach-Churning Rating of 5/10. So you were probably safe anyway; if not, share your tale of revulsion in the Comments. 🙂
Edit edit: The specimen is revealing more here; this may or may not help:
What's In John's Freezer? 
Caudal view of the knee joint (left?), but I can’t say the species name !!
Additional pic added above!
consensus in this house is a knee joint, view is either from behind or or with the patella dissected out.
It looks pretty large, some kind of Ungulate?
Agree, it looks like the back of a knee but I think it’s a right. I can see what look like two meniscal cartilages, and what I assume is the posterior cruciate ligament and one of the collaterals.
It looks kinda birdy to me; and kinda big. Ostrich?
I don’t see a fibula, so I will suspect an avian, possibly ratite? caudal aspect of the knee, femur to the right suggesting this is the right leg. Fibula looks removed.
Answer coming tomorrow morning!
OK I’ve left you in rapt suspense long enough. This one was tricky, I fully admit. While features of the animal in question are visible, they take — as anatomy often does — some imagination and subjective judgements to reach the correct answer. Pretty much everyone got the “caudal view of a knee joint” right. But it’s not an ungulate.
The tapering fibula, which you can barely see toward the top right of the images, is certainly not from an artiodactyl (the fibula would be reduced to a small ankle bone, in most taxa), and “just doesn’t look right” for a perissodactyl, especially when the totality of the knee joint is taken into account.
More telling, perhaps, is the distal femur (the condyles). The joint shape there is asymmetrical, with a larger lateral condyle than medial; the “fibular condyle” (which in this animal has many names) projects more caudally and especially distally than the medial. This, along with the curved shaft of the femur that is also barely visible here, helps the lower leg slant inwards to bring the foot back underneath the body. Indeed, the “lateral condyle” has two condyles; the main one (articulating with the lateral side of the tibial plateau) and an accessory fibular condyle, AKA the ectocondylar tuber among some palaeontologists, and having many other names… e.g. this reference: “Andrzej Elzanowski, The avian femur: morphology and terminology of the lateral condyle. Oryctos 7, 1-5”.
The gigantic medial meniscus, as well as the lateral meniscus/ligament that holds the fibular condyle in a sling when the knee is strongly flexed, is also sort of a clue. No one has ever measured it, but to my eyes this group of animals has a larger set of menisci than a mammal of similar size would.
And if you really squint and know your myology, there is a ligamentous loop obscuring the fibula at the top of the images. That loop (called an ansa) is a very characteristic feature; it helps direct the line of action of the iliofibularis muscle to keep it close to the knee joint.
These features together are just found in one mammalian clade- and here are pics of the femur that provide clearer clues:
and
show this morphology (with lateral condyle cut away in 2nd image) more clearly.
So, yes, I’ve already given the answer away– it is from a bird; a ratite; specifically an emu (but you probably could never tell that from an ostrich in this view). Well done Mark, you nailed it! Jaime was very close, too. Thanks for playing, you intrepid few who took a shot at it!
This image is intended as a segue to a bunch of images of mammalian knee joints and skeletons from the RVC’s Anatomy Museum; my final post on that topic; coming up next!
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