MANDIBULAR DENTAL ONTOGENY OF RINGED SEALS (PHOCA-HISPIDA)

X-rays of mandibles from ringed seal fetuses (n = 15), newborns (n = 1 2), and young-of-the-year (n = 11), collected up to early June, were e xamined for the presence, location, and eruption patterns of deciduous and permanent teeth. The presence of a neonatal line and cementum in permanent canines was determined microscopically. Fetuses sampled in O ctober-November had only unerupted, deciduous tooth germs, but by late January there were robust, deciduous teeth at i1-2 cl pc2-4 and small permanent teeth at I1-2 C1 PC15. In newborns collected in early April , 109 of 143 (76%) deciduous teeth were resorbed completely. The remai ning 34 deciduous teeth were partially resorbed; six (18%) had erupted and likely would be shed. By late April young-of-the-year had no deci duous teeth remaining. In newborns 54% of the permanent teeth (102/188 ) were erupted < 2 mm, and by late May the permanent dentition was eru pted fully. The neonatal line first appeared in the canine teeth of yo ung-of-the-year collected in mid-April and was 100%, present after ear ly May. There was no cementum apparent on any canine collected up to e arly June. Two seals were missing one and two permanent incisors, resp ectively. No supernumerary teeth or morphological variants were observ ed.