Police say the baby was in a car seat but not buckled in when the 16-year-old father tossed the seat toward the baby's 15-year-old mother Friday evening.
Police say the car seat struck a concrete step, tipped and spilled the baby onto the front step of an apartment building. The baby began crying, was quickly picked up and did not appear to be hurt.
The father was taken to the Juvenile Reception Center on suspicion of second-degree reckless endangerment.
WISC-TV reports Dane County Social Services was notified.