The Jaguares won the South African conference and secured a home quarter-final in Super Rugby when they outplayed the Coastal Sharks 34-7 in Buenos Aires on Saturday.
Full-back Emiliano Boffelli and winger Sebastián Cancelliere scored two tries each as the home side romped to a bonus-point victory after leading 12-0 at half-time.
The winning margin could have been much wider as fly-half Joaquín Diíaz Bonilla missed four of eight shots at goal and Boffelli failed with his only penalty attempt.
Topping the South African table confirmed the progress of the Jaguares, who won just four matches of 15 three years ago in their debut season.
Beating the Sharks gave the South Americans a 10 win-five loss record this season and they are set to triumph at home to bottom team the Sunwolves next Friday in the final league round.
If the Jaguares win, they will finish second overall behind runaway leaders the Canterbury Crusaders of New Zealand, and enjoy home advantage again if they reach the semi-finals.
The Crusaders, seeking a third consecutive title and 10th overall, are on 58 points having completed their 16-match regular season schedule.
Jaguares have 46 points and the ACT Brumbies from Australia 43 and both are assured of home quarter-finals, along with the fourth-placed Wellington Hurricanes from New Zealand.
"Winning the South African conference with a match to spare is a wonderful achievement for us," said Jaguares skipper and centre Jerónimo de la Fuente.
'Job well done'
"The side did not start the season particularly well, but winning twice on our last visit to South Africa and winning three of four matches in Australasia turned it around.
"I congratulate all the players in the squad, the coaches and the management for a job well done. We have worked hard and deserve whatever success comes our way."
Sharks skipper and scrum-half Louis Schreuder said: "We had to start well to have any chance of winning here, but instead we found ourselves on the back foot for most of the first half.
"We conceded too many penalties during the opening 40 minutes, which often turned promising attacking situations into a need to defend near our tryline.
"However, we are not out of the running for a quarter-finals place. If we can beat the Stormers in Cape Town next Saturday, I believe we will make it."
Cancelliere held off rival winger Makazole Mapimpi to score the first Jaguares try after only four minutes and Boffelli then got his first, which Díaz Bonilla converted for a 12-point advantage.
Instead of scoring to nudge back into contention, the Sharks conceded further tries to Boffelli and Cancelliere and trailed 29-0 by the hour mark.
The Sharks finally scored 12 minutes from time at Estadio José Amalfitani when centre Andre Esterhuizen powered over after a rolling maul and full-back Curwin Bosch converted.
But the Jaguares had the final say in the 80th minute when winger Santiago Carreras ran on to a grubber kick and dotted down for his first Super Rugby try.