Things to Make and Do, part 3b: Wallaby feet

November 6, 2009

I’m following up immediately on my last post because I am having so much fun with my wallaby carcass.  As you’ll recall, I was lucky enough to score a subadult male wallaby from a local farm park.  Today, we’re going to look at its feet.

Wallabies are macropods; together with their close relatives the kangaroos and Wallaroos, they make up the genus Macropus, literally “bigfoot”.  So wallabies got there long before cryptic North American anthropoids.  And indeed their feet are big.  Here are those feet, in dorsal view, from before I started doing unspeakable things to my specimen:

2009-11-02-DSCN7332

Bennett's wallaby, hind feet in dorsal view

From here they look pretty weird, but it’s only when we go round the back that we really see how odd they are.  Same feet in ventral view:

2009-11-02-DSCN7333

Bennett's wallaby, hind feet in ventral view

There are (at least) three things to notice here: first just that the feet are very long; second, the thick, scaly pad that runs all the way up to the heel; and third, the bizarre arrangement of toes.  At first glance, it seems that there is one main toe and a smaller one each side, but if you look more closely you’ll see that the medial “toe” is really two tiny toes closely appressed, so that they function as a single toe.  This condition is known as syndactyly, Darren tells me.  Also from Darren: it’s digit I that is missing in macropods, so the tiny-toe pair are digits II and III, the main toe is IV and the lateral one is V.

(By the way, seeing my patio in these photos reminds me of something I forgot to mention in the previous post: it’s surprisingly difficult to wash wallaby blood off paving slabs.  Remember that, kids, it’ll be on the test.)

Regular readers will remember from last time that I planned to prepare the skull and left fore- and hindlimbs by simmering and dissection, and let nature deal with the rest of the elements.  You’ve already seen the skull, so here goes with that foot.

After an initial simmer, I was able to skin the left pes, so here it is at that stage, in medial view:

2009-11-04b-DSCN7390

Bennett's Wallaby, left pes in medial view, skinned and simmered

From this angle, you can clearly see the absurdly thin second metatarsal (MT II) that supports the innermost of those two tiny digits.  MT III is just as long and thin, but is fused proximally to the much larger MT IV, as we shall see below.  The simmering has resulted in the more distal phalanges breaking away from their more proximal brethren, and being pulled downwards and beneath them.  This is most apparent with the tiny digits, whose supporting phalanges are clearly visible poking out above the claws.  So the large lump of what looks like cartilage at top right is actually phalanx IV-I, with IV-II and IV-III (the ungual) beneath it.  Also note the significant amount of resilient tissue below the metatarsals.  I’ve cut most of it away, but you can get a good idea from the bits that are still attached distally.

Here is the metatarsus in ventral view after I had removed the phalanges:

2009-11-04b-DSCN7397

Bennett's Wallaby, metatarsus in ventral view, skinned and simmered

Here you can clearly see the syndactyly (in those two closely appressed thin metatarsals II and III at the top of the picture) and the very sculpted distal ends of the  larger metatarsals IV and V.

Now let’s skip straight to to the completed stripped-down pes, now in dorsal view:

2009-11-06b-disarticulated-left-pes-in-dorsal-view-DSCN7419-and-a-half

Bennett's wallaby, left pes in dorsal view, disarticulated and cleaned skeleton; ungual sheaths removed from bony cores.

It’s interesting that the phalangeal formula is so uniform: 0-3-3-3-3.  That is, all four digits have two normal phalanges and an ungual.  But the differences in proportions between them are quite something.

This is our first look at the tarsals — those seven bones on the left of the picture, before we get to the metatarsals.  The three big ones fit together very nicely.  At the back you see the calcaneum, where the achilles tendon attaches; next is the astragalus, which sits on top of the calcaneum and where the distal end of the tibia articulates. Next up is a bone whose name I don’t know, being pretty darned ignorant of ankles — might it be the cuboid?  Anyway, even after cleaning and cartilage-removal , this articulates very nicely indeed with both the calcaneum and MT IV.

Medial to these (i.e. below them in the picture) are four much smaller tarsal bones whose identity I can’t even guess at.  It’s not clear to me how they articulate with the big tarsals — they were all pretty solidly embedded in cartilage and gloop and I fear that they’re not going to fit neatly whatever I do.  Hints will be welcome.

One big surprise was the small bones between the metatarsals and their corresponding phalanges: one each at the ends of MT II and MT III, and two each at the ends of MT IV and MT V.  Because the proximal phalanges articulate so nicely with their metatarsals, it’s clear that these small bones were not positioned between them in life, but rather floated above them — rather as your kneecap, or patella, floats above your femur-tibia joint.  They are sesamoids.  Does anyone know whether this sesamoid formula of 0-1-1-2-2 is common?  Seems a bit weird to me.

Finally, I leave you with the entire left hindlimb: foot as in the previous picture, surmounted by the tibia and fibula, then by the femur, all in anterior view.  Just to the left of the femur-tibia joint is a small bone which I assume is the patella.

2009-11-06c-disarticulated-left-hindlimb-in-dorsal-view-DSCN7424

Bennett's wallaby, disarticulated left hind limb in dorsal view

Special bonus wallaby limb: over there on the right is the left forelimb.  As you can see, I’ve done the easy part (scapula, humerus, ulna and radius) but I still have to dissect out the bones from the wrist and hand — a picky, tedious job that to be frank I am not looking forward to.  The feet are much more exciting than the hands.

That’s all for today.  On Sunday evening I am off to London to spend a whole week in the company of the Archbishop.  The plan is to spend Monday to Wednesday taking final publication-quality photos (I finally have a proper tripod) and digging out field photos and suchlike from the museum archives, then take Cervical U to be CT-scanned at the Royal Veterinary College, courtesy of theropod hindlimb mechanics guru John Hutchinson.  Friday is emergency backup in case something crops up to delay the scanning, and also gives me a chance to retake any photos that didn’t come out as required.  The plan is that this visit should give me everything I need (pictures, measurements, observations, historical documents) to finish up the long-overdue Archbishop description.  Fingers crossed.

I leave you with a puzzle.  This is the jacket that I have designated “Lump Z”:

lump-z

Brachiosauridae indet. BMNH R5937, "The Archbishop". Unidentified elements "Lump Z". Image copyright the NHM, since it's their material.

Can anyone offer a guess as to what this is, and which way up it should be?  It’s a jacket that was opened years ago — before I was involved with the specimen — but never fully prepared.  Matt and I have discussed it a little, but I don’t want to prejudice anyone with our guesswork, so I leave the floor open.  What is it?

SV-POW! Dollars are at stake!



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27 Responses to “Things to Make and Do, part 3b: Wallaby feet”

  1. Nima Says:

    I have a guess for what that “Lump Z” is.

    It’s two dorsal vertebrae (or at least their upper portions/neural arches), photographed upside down with the neural spines at the bottom. They are NOT in perfect alignment, but rather have come apart much like opening a book.

    The vertebra on the left is in posterior view, the one on the right is in anterior view.

    The two may have been joined at one point, or, if they are not consecutive dorsals, may have been jumbled into this position.

  2. Allen Hazen Says:

    My sense is that phalangeal formula– though not as rigid as number of cervical vertebrae– tends to be conserved in mammals. (Whale flippers, of course, providing exceptions.)

  3. DD Says:

    Really interesting, those big feet with reduced numbers of toes, compared to ostrich, emu, rhea, horses etc. I guess there could have evolved a leaping single-toed roo at some point, and if it had a habit of conserving energy like a flamingo, standing on one leg, well, that would have been inspiring, a macro-pogo-uni-pod.

  4. LeeB Says:

    DD,

    you are prescient.
    Sthenurine kangaroos like Sthenurus, Simosthenurus and Procoptodon did evolve single toed feet.

    And Mike, with regard to the wallaby foot, are those two inner claws used as a comb for grooming?

    LeeB.

  5. Nathan Myers Says:

    Nothing published here has given us any hint as to how the immature-wallaby meat tasted.


  6. Nathan, the carcass was fresh enough that I did semi-seriously consider eating some of the meat; but it didn’t seem worth the risk, so I can’t tell you what it tastes like. I can tell you, though, that when it’s simmering it smells like lamb.


  7. Those pedal sesamoids are odd. How common are they in mammals? I’ve never noticed them in any of my skeletons, but they seem like the kind of thing to go easily unnoticed.


  8. Mike, I am emailing you a couple of pics of a _M. rufus_ foot (incompletely cleaned by dermestids) showing how those medial tarsals fit against the bigger bones.

    There’d have been no risk from eating the wallaby; they are phylogenetically distant enough that no internal parasites are transferable. Kangaroo meat is often compared to venison, and is very low in fat (like rabbit). Best after hanging a bit, though you can’t buy it like that in the shops over here (butchers basically have no idea what to do with macropods, unfortunately).


  9. I enjoyed the Varanus salvator carcass we mounted at the university when we were undergrads. I miss it. I think I need to find a wallaby or something… :)

  10. Darren Naish Says:

    You shouldn’t have been afraid about eating some of it; there’s a long and noble tradition of eating deceased zoo animals and I know taxidermists and zoologist who routinely sample roadkill and such. What’s wrong with it – you eat dead animals every day, macropod meat is highly edible (and already available commercially), and you aren’t at risk from anything. Except anthrax.

  11. Darren Naish Says:

    I was kidding about the anthrax. People contract anthrax from cattle, sheep, goats and horses – not from macropods, so far as I know.

  12. Jaime A. Headden Says:

    Mike, your lump looks like a potential mass of metatarsals/metacarpals with highly ossified distal epiphyses. If that object represents a single bone, I would fairly argue it could only be pelvic or sacral.

    As for the wallaby, I do wonder: You render the material, but have you taken the time to dissect it first to prep the bones, then boil the material? Personal removal of material, especially in a wallaby, can eludicate ligamental and tenontal structures, as well as the observation of cartilage to underlying bone shapes.

  13. William Miller Says:

    >>and already available commercially

    Seriously?? Kangaroo meat actually is sold commercially? I wouldn’t have been surprised to hear that hunters in Australia ate some, but … where does the market get them? Are there kangaroo farms, or is market hunting allowed, or what?

  14. Vertebrat Says:

    Wikipedia says it’s wild, not farmed. Makes sense, since roos are often considered pests in Australia.

  15. davidmaas Says:

    There’s an Aussie restaurant in Berlin. They sell crocodile and kangaroo dishes. Do quite well too. I asked them about their sources and they said they buy from farms.

  16. Nathan Myers Says:

    Kangaroo meat is supposed to be illegal to import to the US. The story I got was that a congressman’s wife heard about an endangered wallaby, and got him (not the wallaby) to introduce a measure banning them (not the congressman and his wife) here. Since, to USers, all kangarooids are alike, they’re all banned, not just the endangered ones.

    So, commercially available; just, not here.

    My question for the assembled is, ought “kangarooids” to be pronounced “kangaroo-ids” or “kangaroo-oids”? In case of disagreement there will be a cage match.

  17. John Scanlon Says:

    Odd, the comment I sent yesterday didn’t get through. I said something about how safe it is to eat macropods (also that like other low-fat game meats it’s best hung for a couple of days, but you can’t buy it like that anywhere), and that I was sending Mike photos of a semi-cleaned red kangaroo foot with the medial tarsals in place. Did the email get through, at least, or should I try again?

  18. Graham King Says:

    Nathan: ..”kangaroo-ids” or “kangaro-oids” surely?

    (It puzzles me how “zoo-ologists” get away with pronouncing one of their “o”‘s twice. Isn’t that cheating? Shouldn’t it be pronounced either “zool-ogy” or “zo-ology”?
    Purists unite! Do I scent a factional split in the offing?)

    Mike: more fascinating stuff! In Edinburgh the National Museum of Scotland has a macropod skeleton mounted in life-like pose (leaping), in which its syndactylous toes can be nicely seen.


  19. Macropod-oids! Or informally ‘macropods’, the clade of all ‘kangaroos’, ‘wallabies’ and ‘rat-kangaroos’ (which are roughly size-classes rather than clades).

    There are also family-group names derived from Potorous (Potoro-idae), and extinct genera ending in “-roo”, e.g. Balbaroo, basis for family name Balbaridae, where the “oo” has been simply dropped in forming the stem (not exactly standard Latin grammar, but nobody’s made a fuss about it).

    I used to fluctuate between saying “zoo-ology” and “zo-ology”, but try to stick to the latter. Nobody would ever get away with “zoo-logy”.

    I wonder if this comment will get through, my last two didn’t.

  20. Nima Says:

    I’m just curious… Is there any new news on the identity of the Archbishop specimen? Or the SV-POW bucks?

  21. Mike Taylor Says:

    Thanks to all who commented on the identity of Lump Z. It’s useful to see the different ideas. Jaime, while I am far for sure about its identity, I am at least confident that it’s not metapodials — there is enough lamination that it has to be vertebral. Nima, your idea is probably closer. Having looked at Lump Z again this last week, and discussed it with Paul Barrett, I am currently thinking that the most likely interpretation is that the left half may indeed be an upside-down dorsal neural spine, probably in anterior view, but the right half might be the right diapophysis, bent upwards (i.e. downwards as we look at the photo).

    John, many belated thanks for the kangaroo-foot photos: useful!


  22. […] centra and a dorsal spine, some scap scraps, a partial ?pubis, a long-bone fragment and “Lump Z“, whatever that is.  What you see above is my best photograph of what I’ve designated […]


  23. […] bits from time to time. Not that we haven’t been doing that anyway–heck, even wallaby toes are not safe  from our roving curiosity–but we’re going to stop marking such posts […]


  24. […] is indeed Logan the wallaby from waaay back in late 2009. Here’s how I butchered him, and some detail on his feet, and how his skull  turned out. Back then I prepped out a forelimb and a hindlimb, the skull and […]

  25. kmccready Says:

    Stumbled on your page. Well done. I did the carpals of Wallabia bicolor.
    https://kmccready.wordpress.com/2014/07/03/carpals-of-swamp-wallaby-wallabia-bicolor/

  26. Mike Taylor Says:

    Wow, that is some beautiful, careful work! It inspires me to want to reconstruct my own wallaby’s wrist — something that I’d previously more or less despaired of, but now, with your post’s help, may well be able to do.


  27. […] Майка — палеонтология и динозавры (публикации и блог по теме). Тем не менее блог The Reinvigorated Programmer посвящен […]


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