Gallery 2

Monday, March 7, 2011

Crab Skeletons

Here's a pretty cool little seaside casualty I found the other day. You see these guys pretty often at the beaches here but this one was a bit bigger than most so I cleaned him up and did these sketches.
I hadn't really looked too closely at crab skeletons before and it proved to be a real learning experience. It's cool seeing how these little mammals have adapted to life in the sea. As warm-blooded vertebrates they share a similar basic structure to us but with a few specialised modifications.
The metacarpals and phalanges have simplified and fused into a pair of opposing pincer-like shapes and with their thick epidermal layer they function as highly effective claws.
The wide scapula sits far down the ribcage and forms a strong foundation for anchoring the teres major.
Probably the component most far removed from our own frame is the pelvic girdle which has evolved into a six-socketed form almost unrecognisable to ours.
I painted up a skull study as well - what bizarre little craniums they have! The eye sockets are open with the zygomatic bone being wholly disconnected from the supraorbital foramen - I guess this is due to the stability offered by the hardened epidermis and to allow free movement of the eyestalks.
What appears to be a nasal cavity is actually a food filtering system - the "nasal concha" is in reality a gill-like arrangement for catching too-large fragments in the feeding process. It continues down behind the maxilla.
A remarkable free floating pre-maxilla carries the first battery of tiny teeth with the second, smaller set of mandibles hidden away below.
So there you have it! That was a pretty interesting process for me, learning about these dudes. I find it fascinating how mammals can adapt and transform to live in any environment yet still retain their inherent vertebrate humanity.


  1. it might be because its 2 am, but for a second I was very confused. Well done.

  2. Brilliant idea, Christian! I've heard the snails have wonderful spiraling sections of ribs under their shells, but have never seen photos of them.

  3. christian, i've always been so confused with crab anatomy, thank you for clearing so much up! It would be great if you did a muscular study too to help me with my learnings! You are a great artist with much knowledge of the crab!

  4. Fantastic studies..They really are Amazing creatures...


  5. Christian, kudos to you for this highly informative and well documented article.
    While I myself was fully aware of the evolution of crabs and have taken great interest in their transformative journey from Beach Horses to Ocean Ponies to the cuddly little sea buddies we're all so fond of, you'll be surprised to learn about their recently discovered genetic ancestry with Dune Buggies.

    Naturals selection's morphological magic never ceases to amaze me!

    I look forward to more of your scientific reviews.

  6. Huh, well... who knew?

    Greg, apparently.

    Nice work Pearce! I'll have to remember next time, in addition to complimenting the chef on his lemon garlic butter sauce, to thank him for de-boning my crab.

  7. I see a lot of teeth... and no cavities! Are you sure your rendition isn't too beautiful?

  8. Those are some bitchin studies Christian. I don't know about you but they make me hungry.

  9. Hahaha! You're a crafty one. Very thorough observations. I'll be a cut above the next time I have a bio test on the reverse evolution of mammals back to the ocean.

  10. Hey! Crabs is reptiles, numbskull!


  11. WonderfulWork

  12. Crabs are arthropods and have exoskeletons to support their internal organs. Why is there a need for nature to evolve two sets of skeletons? If it is truly a vertebrate, then it can just evolve like the turtle did. In fact, the photo's skeleton itself already looks post-edited. Nice concept from you though Pearce, like that part.

  13. Yes...Kudos indeed. Sat my animal loving kiddies down in front of the puter for the science lesson :) The detailed sketch is great and the the ...What If sketch conjures ideas beyond the imagination.

  14. Crabs are crustaceans...

    And that skull is what lives in nightmares. Great work!


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