Skeletons In My Closet
The Fisher Diaries – Part 5

What a pain in the ***, I mean carpals and metacarpals!

This project was shifted to the backburner for a while and I am finally getting the posts updated on it now. That’s one of the great things about an articulation project – once everything is cleaned and ready to assemble, you can take all the time in the world to work on it… it isn’t going anywhere!

For these more complicated articulations, I switched to The Small Mammal Manual Manuscript by Lee Post for more in-depth species-specific information. Lee’s suggestion in his flow chart for building a skeleton was to start with the four feet to get the most tedious part over with while the enthusiasm for the project is high. I had various reasons for not following this advice; mostly intimidation of all those little bones, the complexity of the pose I wanted to capture with various degrees of weight bearing in each limb, and did I mention the intimidation factor?

Name and Identification Please

When taking on the challenge of articulating the bones of the foot, it helps to make sure you can identify each bone before you start assembling them. I used the bone identification chart to help identify the seven carpal bones, placing them on a labeled index card to help keep them organized. This worked well until I had identified all the bones I was expecting and there was one little one left over. I confirmed that the same little mystery bone was present in both front feet, so I was pretty confident it belonged there, but I had no idea what it was or where it went. I decided to continue with the articulation while I did some extra reading to sort out who this unexpected character was.

Identifying the carpal bones helps with determining which metacarpal goes where. Once you determine a solid starting point (for me it was the grouping of the hamate and the 4th and 5th metacarpals) you can build out from there, very much like a 3D jigsaw puzzle. The 3rd metatarsal articulates with the capitate, the 4th metatarsal with the trapezoid, and the 5th metatarsal with the trapezium, and then they all go together beneath the scapholunar. The most difficult bones to position were the triquetral and pisiform and I am very grateful I was using Elmer’s clear glue which allowed me to reposition them several times.

Mystery solved!

Note details of the pads of the forepaws, it will be interesting to compare these to the actual skeletal structure during articulation.

Once I had the carpals and metacarpals assembled, the small articular surface at the base of the first metacarpal became apparent as the home of the mystery bone. I compared the photographs I took of the fisher’s paws at the start of the project and was thrilled to see a corresponding pad in that area of the foot (it is the little round pad on the upper right side of the photo shown here between the large wrist pad on the right and the multiple pads at the distal ends of the metacarpals). Digging a little deeper, I found a great journal article titled Evidence of a false thumb in a fossil carnivore clarifies the evolution of pandas that explained in detail the presence of several anatomical features of arboreal musteloid carnivores and I am fairly confident that this mystery bone is a radial sesamoid which would aid the fisher in climbing trees with ease.