Two hundred forty-two specimens of Onychomys leucogaster, ranging in age from day of birth to the twenty-eighth day were cleared and stained using both Alizarin KOH and Alcian Blue/Alizarin-Trypsin staining methods. Thirty centers of ossification were studied. The data demonstrate the following: 1) skeletal centers of the appendicular skeleton ossify and mature earliest; 2) a new sesamoid bone lateral to the distal condyles of the femur was discovered; 3) the skeletal ossification of the baculum is present at one day of age; 4) a high degree of individual variation precludes aging of this species by skeletal maturation.
Bailey, Joe W. and Heidt, Gary A.
"Postnatal Osteology of the Northern Grasshopper Mouse, Onychomys leucogaster,"
Journal of the Arkansas Academy of Science: Vol. 38
, Article 5.
Available at: http://scholarworks.uark.edu/jaas/vol38/iss1/5