Tupuxuara’s wrist: the carpals and pteroids

The carpals are seven little bones which connect the metacarpals, pteroid and radio-ulna pair together. I had no sources for Tupuxuara, and after spending a day trying to make a pair of syncarpals (fused carpals) from Tapejara, I decided to use Anhanguera as a source. So my Tupuxuara’s wrist actually belongs to Anhanguera.

There are five distal carpals, and four of them are fused together so they actually act as two: the distal syncarpal, which articulates the hand metacarpals, and the pre-axial carpal which articulates the pteroid. There are two proximal carpals, also fused, which connect to the radio-ulna pair. I used Anhanguera (Kellner and Tomida 2000) which provides four views of the proximal and distal syncarpals. I made up the medial carpal (roughly based on other pterosaurs and drawings). I adapted the pteroid from Pteranodon and adjusted its size by a low resolution Thalassodromid fossil photograph (it was not good enough to use the photo as an image source, but I could calculate its proportions relative to the radio-ulna.

This was a first test carving just the two syncarpals, but I didn’t use it. I decided to make individual carpals.

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I printed the four views of each syncarpal and coloured each carpal differently to make it easier to identify them on each view.

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Then I carved the individual carpals from 3 cm XPS foam. These are the carpals that form the left and right distal syncarpals.

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This is the distal syncarpal assembled (showing the side that articulates with the proximal syncarpal).

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These are the parts that make the left and right proximal syncarpals.

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And these are the proximal syncarpals assembled.

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Since they are usually fused (in mature pterosaurs), I glued them together with silicone glue (which retains some flexibility). Here is a view of all the syncarpals (showing the sides that connect to each other).

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Now the other side. This is the side that connects to the bones (proximal syncarpal to radio-ulna, and distal syncarpal to the wing metacarpals.

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Anterior view.

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Posterior view.

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This is the distal end of the radio-ulna pair with the carpals connected. The bone that is pinned at the right is the pre-axial carpal. It articulates with the pteroid (via a sesamoid bone) and with the distal syncarpal. The Anhanguera specimen I used as a source didn’t have one so I “invented” one based on some photos of Pteranodon fossils (I used the article “Articulation and Function of the Pteroid Bone of Pterosaurs”, by S. C. Bennett, 2007 as a source).

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Here are some side views.

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Now the pteroid. It has a very thin and fragile tip. To make it stronger I stretched a piece of PVC plastic (from a plastic hanger) to serve as a bone skeleton.

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I used two halves of 5 mm XPS foam, and a plastic bone skeleton.

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Opened a cavity on both sides and sandwiched the plastic skeleton inside.

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After carving, staining, etc. we have a pair of pterosaur pteroid. Here is the full collection partially connected. The pteroid connects to the sesamoid bone, which connects to the pre-axial carpal, which connects to the distal syncarpal, which connects to the wing metacarpal.

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And now our Tupuxuara has a wrist and pteroid.

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We still need fingers (including metacarpals), feet (including ankle bones), tail and pre-pubis. I’m not sure I will have time to include the pre-pubis this week. I might leave it for later when I plan to make some minor fixes and possibly introduce new ribs, gastralia and cartilage (in silicone rubber).

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1 Comment

Filed under Pterosaur #5: Tupuxuara

One response to “Tupuxuara’s wrist: the carpals and pteroids

  1. Pingback: Making of a Tupuxuara | The Imaginary Pterosaur

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