Comments on: Mystery Dissection 5: Double Dutch

By: gingerest

gingerest — Mon, 30 Apr 2012 03:29:59 +0000

That is super, duper cool.

By: John of the Freezers

John of the Freezers — Sat, 28 Apr 2012 07:13:30 +0000

OK, I’ve dragged this out long enough. There have been great guesses and even the ones that were wrong have some good deductive processes behind them, so in a way we’re all winners. But in a more accurate way, Jason (and his team of ringers) pretty much nailed it in the first comment. Way to go, Jason! Bask in the glory of your peers’ adulation. Many others deserve at least partial credit and perhaps more muted adulation for getting at least part of the answer.

The top pic is the extensor digitorum longus [communis]/common digital extensor. The bottom pic is the flexor digitorum longus, or even more properly the deep digital flexor (flexor digitorum profundus), which is somewhat divided into medial and lateral heads.

One thing to note is the massive size of the flexor vs. the extensor (muscle bellies as well as tendons– note the typically flat tendons of the EDL and the nice stout round tendons of the FDP), as is typical in land animals. In that animal, the EDL weighed a paltry 0.59 kg whereas the FDP weighed a hefty 1.2 kg. And thanks to the shorter, more angled muscle fibres in the FDP, it could produce not two times, but almost FIVE times, the force of the EDL- about 0.28 vs. 0.063 body weights!

So what animal is it from? The size of the muscles is now a clue, but I removed the scale from the pic so you couldn’t use that (although it still had a gestalt of large size, maybe?). It’s from a forelimb; that’s hard to tell.

Gingerest was really thinking properly about this– it has four toes (one tendon in the FDP was cut a bit short). And many people know that I tend to work on big animals. This one was bang on at 1600 kg body mass. So that pretty much answers it- a 4 toed, 1.6 tonne animal can only be a common hippo. Hurrah!

And to put that 0.28 body weights of relative force into context, this 1600kg hippo could have curled its wrist and fingers with about 440 kg worth of force (about Schwarzenegger bodyweights)– take that, Ahnold!

By: Amber Alink

Amber Alink — Sat, 28 Apr 2012 06:50:47 +0000

Front leg and rear leg musculature and tendons of an elephant.

By: eotyrannus

eotyrannus — Fri, 27 Apr 2012 09:16:57 +0000

Could it be, I wonder… something like the triceps of a big artiodactyl? Specifically… Giraffa? I dunno, just has that vibe. My first comment here at your awesome blog. May it serve me well.

Darren

By: Mark Robinson

Mark Robinson — Fri, 27 Apr 2012 06:30:27 +0000

Late to the party… I have to concur that they look to me like the mammalian equivalents of “drumsticks” – flexor digitorum whatever they are in animals.

Scale-bars would obviously help to narrow them down species-wise but the top one looks to be about a metre in length so I’d say it’s from a giraffe. The bottom one looks to be about 2/3 the length of the top one. I wouldn’t have thought that elephants would have such large muscles for flexing their digits (altho’ could assist with locomotion, I guess) so I will say it’s from a hippo.

I am a little more confident of the species in the lower-right of the bottom pic though – Musca domestica.

I wait to be educated (which will no doubt happen no matter how accurate my guesses are).

By: gingerest

gingerest — Fri, 27 Apr 2012 01:01:19 +0000

I have no knowledge but I enjoy puzzles.My belief: both are flexor muscles for a locomotive limb. (Not a flying or swimming limb – a walking or running limb.) Both are for animals that require some separate use of the digits, from the fact the digit tendons are separate, but there must be some other muscle providing those fine controls.
The upper one is for an animal that walks on four digits, and the lower for an animal that walks on three digits and has a fourth placed elsewhere. Wikipedia says the term for that is anisodactyly.
I can’t tell whether the upper animal has a fifth digit controlled by a different muscle, or has has lost its fifth digit. The long distance between the muscle itself and its points of attachment suggests a long moment arm and greater leverage, in contrast with the lower animal, which has a very bulky muscle set comparatively close to its attachments. Maybe the top animal does a bit of running around on that limb and the lower one is heavy and stands around a lot?

By: rjm

rjm — Fri, 27 Apr 2012 00:02:53 +0000

I only know human anatomy, but I remember how mush dissecting the human upper arm put me in mind of turkey drumsticks….. looks to me like some type of forefoot/forearm leading to the digits.

By: Robyn

Robyn — Thu, 26 Apr 2012 23:33:04 +0000

Whale?

By: Fiver

Fiver — Thu, 26 Apr 2012 20:04:12 +0000

Gorilla arm?

By: Dave

Dave — Thu, 26 Apr 2012 18:37:00 +0000

Ok. I’ve just had a quick search, and realised that my earlier answer shows that (almost literally) I don’t know my arse from my elbow. I’m now with flexor digitorum, and know enough to know that I don’t know which…