In the wake of a 500-point market selloff this afternoon, the business networks are planning extended coverage well into the evening tonight. On CNBC, Brian Sullivan, Simon Hobbs and Amanda Drury will anchor “Special Report: Markets in Turmoil” from 8 p.m. to 10 p.m. David Asman will anchor coverage on Fox Business Network at 9 p.m. with a special edition of “America’s Nightly Scoreboard” called “Special Report: Market Selloff.”