Franck Kessie stepped up from the penalty spot to send defending champions Senegal tumbling out of the Africa Cup of Nations and spark wild celebrations in Yamoussoukro.
Kessie had given hosts Ivory Coast hope when he coolly dispatched an 86th-minute spot-kick past Senegal goalkeeper Edouard Mendy to send the tie into extra-time.
The 27-year-old delivered once again with the crucial kick to seal a 5-4 win in the shoot-out after Moussa Niakhate had missed his earlier effort for the favourites.
The Ivory Coast’s win continued a remarkable revival for the hosts who had looked down and out in the group stage after a 4-0 humiliation at the hands of Equatorial Guinea.
Senegal had looked set to end the curse that had seen no defending champions reach the last eight since 2010 when Habib Diallo rifled home with just four minutes on the clock.
The hosts responded well as they pinned Senegal back in their own half, but the holders’ defence held firm and Ivory Coast were restricted to a succession of half-chances.
Seko Fofana’s run into a dangerous area was superbly snuffed out by Niakhate and Senegal almost extended their advantage on the stroke of half-time when Ismaila Sarr stumbled over a shooting chance.
Sarr came close again early in the second half but Ivory Coast continued to press through Oumar Diakite, who almost served up a leveller for Jean Philippe Krasso just before the hour mark.
The holders missed an even better opportunity in the 74th minute when Kessie’s free-kick was parried by Mendy, who somehow got in the way of the same player’s follow-up from a tight angle.
Substitute Nicolas Pepe missed another huge chance when he lashed a curling effort straight at Mendy, but earned his side their crucial penalty four minutes from time when he was tripped by Mendy in the box.
Kessie kept his cool to force the additional half-hour and after neither side could break the deadlock, it came down to the shoot-out where the hosts scored all five to seal a famous triumph.
Cape Verde edge past Mauritania to book quarter-final spot
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Highlights of the AFCON round-of-16 match between Cape Verde and Mauritania
Ryan Mendes converted a late penalty as Cape Verde beat Mauritania 1-0 in Abidjan to seal their place in the quarter-finals of the Africa Cup of Nations.
Cape Verde captain Mendes struck the decisive spot kick in the 88th minute and the Blue Sharks will now face either Morocco or South Africa in the quarter-finals.
Cape Verde, one of the surprise teams of the tournament after finishing unbeaten at the top of Group B ahead of Egypt and Ghana, were second best for most of the first half, but finished strongly to secure their passage.
Mauritania reached the tournament’s knockout stages for the first time by defeating two-time winners Algeria 1-0 in their final group game to progress as one of the best third-placed teams.
The first-half action was end-to-end, but clear-cut chances were at a premium, while Mauritania were dealt a blow in the 35th minute when Omare Gassama was carried off on a stretcher and replaced by Guessouma Fofana.
Cape Verde’s Ryan Mendes (R) celebrates after scoring the winner in Abidjan
Mendes’ early effort for Cape Verde was deflected into the side-netting and Mauritania captain Mouhsine Bodda curled a 15th-minute free-kick just wide.
Mauritania made all the early running in the second period and Souleymane Anne missed the game’s best chance from open play when firing wide after Sidi Amar’s surging run into the penalty area just before the hour mark.
Cape Verde came on strongly in the closing stages with both Garry Rodrigues’ drive and Mendes’ header forcing Mauritania goalkeeper Babacar Niasse into excellent saves.
The game’s decisive moment came in the 87th minute when Yassin El Welly’s misplaced headed back-pass was pounced on by substitute Gilson Benchimol, who was brought down by Niasse for a clear penalty.
Mendes held his nerve, drilling his spot-kick down the middle and the Blue Sharks saw out 10 minutes of added time to seal their place in the last eight.