T-rex toes

[digit]

Here's a (hopefully) interesting question on a topic well outside my wheelhouse. In the break room at the Florida Museum of Natural History sitting on top of the double refrigerators is a cast of a coelacanth, a painted resin cast of a Tyrannosaurus rex foot (the left one), and inexplicably a cleaning sponge that one of the artists at the museum has modeled into a cartoon character named Robert with quadrilateral trousers.

 

I've been looking at these objects while nuking my lunch in the microwave oven next to the refrigerators for several months now. Just yesterday I finally noticed that there was something odd (to me) about the T-rex toes. Leading up to the ultimate distal/ungual on each of the three toes (disregarding the hallux "dew claw") are a varying number of phalanges. Somehow I had naively assumed that the number of phalanges in each toe would for some reason be consistent.

 

For reference, each of the digits in our human hands have two phalanges (proximal and intermediate) leading up to the distal phalanx (ungual) on all but our highly useful opposable thumbs. Our thumb (pollux in medical speak) makes up for the missing intermediate phalanx by having a metacarpal that has more mobility than the metacarpals of our other digits.

 

 

I found it fascinating to learn that the 3 primary toes of a theropod dinosaur, labeled II, III, & IV, have (very conveniently) 2, 3 & 4 phalanges leading up to the distal phalanx. I came across this excellent artwork from a paleoartist online:

 

https://emilywilloughby.com/art/gallery/diagrams/theropod-foot-comparison

 

 

It seems that our modern day dinosaurs (birds) share this same asymmetry in toe bones as the T-rex that started this little investigation. I'm guessing that to those who have taken anatomy or physiology classes or have a deeper understanding of birds or dinosaurs this would be common knowledge but somehow I've never paid enough attention to theropod feet till now. I do so enjoy learning new tidbits of information (quite regularly from this forum). In the off chance that this might be enlightening to other members I thought I'd share my micro-epiphany instigated by some T-rex toes on top of a fridge.

 

Cheers.

 

-Ken