At about 41 postovulatory days old, the embryo measures 11-14 mm in length. Distinct digital rays in the hand plate, which will become the fingers and thumb, and a rounded digital plate in the foot can be seen. Also present are prominences of the lower jaw arch and hyoid arch, the latter being a U shaped bone in the throat that allows for the production of a wide range of sounds that animals cannot produce. The nasofrontal or nose grooves become distinct, and there is a slight indication of a lumbar or spinal curvature.