SAN FRANCISCO - Aldon Smith broke the 49ers' single-season sack record by notching No. 18 ½ to open Sunday's second quarter against the visiting Miami Dolphins.

Smith overpowered Jonathan Martin, a Stanford-bred rookie left tackle, to drop rookie quarterback Ryan Tannehill for an 8-yard loss at the 49ers' 17-yard line. Two snaps later, the Dolphins settled for a 28-yard field goal from Dan Carpenter to take a 3-0 lead.

Smith had a sack last Sunday to match Fred Dean's previous franchise record. Last year's first-round draft pick out of Missouri, Smith had 14 sacks his rookie season, and he's tallied more sacks in his first two seasons than anyone since the NFL began tracking stats in 1982.

The 49ers' all-time leader in total sacks is Bryant Young with 89 ½, followed by Charles Haley with 66 ½.