Illustrating Turtle Evolution

New fossils of the earliest-known turtle, Odontochelys semitestacea ("toothed, half-shelled turtle"), have given new, and long searched-for, evidence of how turtle shells evolved. Press release here.

dorsal view

Here you can see the full plastron and the partial shell extensions which grew out to form the partial upper-shell. The take-home messages of this find are:

1. Odontochelys was likely aquatic
2. Odontochelys had a plastron (lower shell) but not a full carapace (upper shell)
3. Odontochelys had teeth! (all modern turtles have toothless beaks)
   

The challenge to the illustrator is to communicate all of these ideas in one image. Illustrator Marlene Hill Donnelly of the Field Museum in Chicago solved this problem in an efficient way: by drawing two turtles! One from above and one from below.

illustration by Marlene Hill Donnelly - click for big!

What a beautiful and bizarre looking creature! For more on turtle evolution, check out the UCMP Berkeley's page on anapsids here.

extra photo because turtles are awesome