Regeneration in the adult salamander, Ambystoma annulatum, parallels that of the adult newt (Iten & Bryant, 1973). However, a number of unique features become apparent upon examination of anomalies of adult regenerates. Two regenerates which displayed gross abnormalities revealed, upon histological examination, unique features which give insight into a possible pattern of digit formation in this species of adult salamander. Normal regenerates show 4 or 5 digits radiating distal to the same respective number of bones (distal carpals) present in the distal row of wrist bones. The first anomaly showed only two large, fused distal carpals and two lateral digits. The second anomaly contained three bones in the distal row of wrist bones and three digits. From the above observations, one might postulate that since the number of digits that will eventually occur corresponds to the number of wrist bones found in the distal row, then the presence of a proper number of wrist bones in the distal row is essential for normal digit development.
Young, Henry E.
"Anomalies of Limb Regeneration in the Adult Salamander, Ambystoma annulatum,"
Journal of the Arkansas Academy of Science: Vol. 31
, Article 37.
Available at: http://scholarworks.uark.edu/jaas/vol31/iss1/37