Deep

     Todays blog is on deep muscles. These are the muscles that ... well no one really talks about. Everyone knows about the biceps and triceps, pectorals and deltoids, but not many people discuss the teres major or the pronator quadratus. My iguana has been almost completely de-muscled except for these deep muscles, and to be honest, I'm not really sure what to be looking for. So Dr. Zack helped me out with two papers on the homologies of tetrapod forearm extensors and flexors. 

     The first paper (Haines, 1939) details the results of a study that compares the forearm extensor musculature of Chelonia (turtle), Sphenodon (lizard), Salamandra (salamander), Ophiacodon (synapsid), the giant salamander, Eryops (early amphibian), Rana (frog), Varanus (monitor lizard), crocodilians (this seems obvious), monotremes (mammals that lay eggs), and Didelphys virginiana (opposum). It was a pretty extensive study. What I took away from it, is that generally species living in similar environments have similar muscles, which makes sense given that they have to do similar things. Evolution is consistent like that especially because this study was focusing specifically on homologies (something that is shared in present species because it was shared by a common ancestor). I also determined that in my iguana I need to be on the look out for brachioradialis, which allows for the rotation of the forearm, supinator manus, which allows for the supination of the hand, and supinator manus accessorius, which helps in the supination of the hand. I believe I have already found the brachioradialis, but the other two I haven't looked for yet.
     The second paper was slightly less in depth (Haines, 1950). It compared many of the same species as the previous study, but really focused on Varanus (monitor lizards) and Felis (cats). The main take away for me was that I need to be looking for pronator profundus, which in humans is often called pronator teres and allows for the pronation of the hand, and pronator quadratus, which does the same. Keep in mind, the forelimb of my iguana is only maybe three inches in length, and on humans these muscles are only maybe an inch or two long. They're tiny in iguanas. 
AA

Haines, R. Wheeler. "A Revision of the Extensor Muscles of the Forearm in Tetrapods." Journal of Anatomy (1939) 73.2: 211-233. Web. 29 Mar 2012. 

Haines, R. Wheeler. "The Flexor Muscles of the Forearm and Hand in Lizards and Mammals." Journal of Anatomy (1950) 84.1: 13-29. Web. 29 Mar 2012.