Verizon has reported a record-breaking number of iPhone sold during the fourth quarter of 2011:

Verizon Wireless, the largest U.S. mobile carrier, sold 4.2 million iPhones in the fourth quarter, more than doubling from the third quarter, said Fran Shammo, finance chief of the company’s parent.

The iPhone sales will narrow gross margins at the wireless business by 500 to 600 basis points, Shammo, chief financial officer of Verizon Communications, said today at a Citigroup Inc. event in San Francisco. U.S. carriers sell smartphones such as the iPhone to subscribers at a loss to get them to sign up for contracts that typically run for two years.

Comparatively, carrier sold 2 million iPhones during the previous quarter.