The deciduous teeth are serrated until they are lost .
Then deciduous teeth are replaced with blade - like teeth , that have evolved to shear along with the molars that also have long shearing crests to help break down the plant matter they ingest .
The deciduous teeth are serrated until they are lost and then they are replaced with blade - like teeth , that have evolved to shear along with the molars that also have long shearing crests to help break down the plant matter they ingest .