Fiorentina grabs first win of 2013
Vincenzo Montella's men were chasing a first win in five games to restore their bid for a Champions League place and veteran striker Luca Toni put them on track with his ninth Serie A goal against Parma.
And the visitors, who are sliding down the league table, were condemned to a second straight defeat when Stevan Jovetic scored five minutes into the second half.
Palermo signed a total of 10 players in January, with Diego Fabbrini and Alejandro Faurlin the last to arrive on deadline day.
They both made their debuts but ended in a losing cause as second-half goals from Carlos Carmona and German Denis put Atalanta in control before Nelson's late consolation for the hosts.
It was a well-deserved first win for new head coach Davide Ballardini, whose side built a two-goal lead inside 21 minutes thanks to goals from Marco Borriello and Andrea Bertolacci.
But the hosts would have to fight to the very end for the three points as Sergio Floccari and Stefano Mauri dragged Lazio back into the game, only for deadline-day signing Rigoni to fire Genoa up to 17th place with a bullet late header.
The home side twice took the lead from the spot through Vladimir Weiss and Gaetano D'Agostino, with Alessandro Diamanti initially equalising with a penalty for the visitors.
And Diamanti then set up a second equaliser for Alberto Gilardino before Panagiotis Kone scored what proved to be the winner midway through the second half.
The win lifted Bologna up to 14th, five points clear of the drop zone into which Pescara slipped due to Genoa's 3-2 win over Lazio.