Richardson recorded the best figures for a home debut in Warwickshire's history.
John Crawley, the Lancashire captain, led by example with his second century of the season against Hampshire at Old Trafford. Crawley's unbeaten 117 enabled his side to reach 352 for 7 in reply to Durham's 226.
Russell Warren and David Ripley steered Northamptonshire to 293 for 6 at Wantage Road in reply to Hampshire's 357. The home team slipped from 197 for 2 to 201 for 6 - losing four wickets for four runs in 31 balls - but Warren and Ripley shared an unbroken seventh-wicket stand of 92.
Graham Rose took 4 for 14 as Glamorgan were bowled out for 113 against Somerset at Taunton. Rose had earlier top scored with 50 as Somerset were bowled out for 203 after winning the toss. The pitch will be reported with 20 wickets having fallen on the first day.
James Kirtley took six for 37 as Sussex beat Essex by eight wickets at Eastbourne. Essex resumed on 121 for 5, a lead of 29, and were bowled out for 155 after 50 minutes. Kirtley took the last four wickets to leave Sussex needing just 64 to win.