Derbyshire blew Somerset away - dismissing them for just 103 – before closing on 220-5 as 15 wickets fell on an extraordinary opening day at Taunton.
Tim Groenewald (5-33) – who claimed his third five-wicket haul of the campaign – and Tony Palladino (4-34) claimed nine wickets between them to dismiss the hosts inside 34 overs.
Karl Krikken's men responded with a 52-run opening stand, before an unbeaten 93-run partnership between Tom Poynton (53 not out) and Richard Johnson (55 not out) pushed home their advantage, as the visitors sealed a 117-run lead at stumps.
Derbyshire did the damage during an astonishing morning session in which the hosts lost seven wickets to slump to 69-7 at lunch.
Mark Footitt (1-25) got the early breakthrough removing former England opener Marcus Trescothick for 17 - and the wickets soon tumbled as Groenewald and Palladino tore through the Somerset top and middle-order.
Groenewald claimed five scalps to return figures of 5-33, including four maidens, off his 13.1 overs and passed 200 first-class wickets for Derbyshire.
Strike partner Palladino – who was making his first LV= County Championship appearance since mid-June – enjoyed similar success claiming the key wickets of Nick Compton (4) and James Hildreth (7) before finishing with four.
Derbyshire made a fine start to their reply thanks to an opening stand of 52 between Ben Slater and Paul Borrington (27).
The visitors lost Madsen (7) and Shivnarine Chanderpaul (4) to fall to 64-3, but Slater helped Derbyshire surpass Somerset’s first innings total just after tea. The 22-year-old – who struck five fours – was finally removed by Piyush Chawla for 45, with Derbyshire 121-4.
It was, however, the sixth-wicket partnership between Poynton and Johnson that ensured the visitors would end the day with the early advantage.
The duo added 93 runs to take their side from 127-5 to 220-5 at stumps, handing Derbyshire a healthy 117-run lead with five wickets in hand heading into Day Two.
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