Argentina outscored Wales seven tries to four on Sunday, quickly ending hopes of a change in fortune for the beleaguered Welsh, who had suffered a record-breaking 18-match losing streak before victory in their last international in Japan in July.
But it is now one win in their last 20 Tests as Geronimo Prisciantelli (2), Pedro Delgado, Simon Benitez Cruz, Mateo Carreras, Bautista Delguy and Santiago Grondona scored tries for Argentina.
Tomos Williams, Dewi Lake, Jac Morgan and Blair Murray went over for Wales.
Santiago Carreras had a 100 percent return with his kicking, slotting over seven conversions and a penalty, while Dan Edwards was successful with his three conversions and Jarrod Evans another.
Argentina sped into a 14-0 lead in the opening 10 minutes as Delgado bulldozed over for a first Test try and Prisciantelli outsprinted the home defence to get onto the end of a chipkick.
Wales responded with two tries of their own, the first from Williams and then Lake bursting over from short distance, allowing the home crowd some optimism after 20 minutes.
But when Ben Thomas was sin-binned for kicking out at Pablo Matera, Argentina took advantage, with Benitez Cruz stretching over from close range to score.
From the kick-off, Matera burst through the Wales midfield before kicking out to the left where Mateo Carreras sped onto the ball to score for a 31-14 halftime lead and a sucker punch to Welsh hopes.
This was increased when Delguy scored four minutes after the break before Wales skipper Morgan lifted home spirits by bursting over for a try in the 54th minute.
But he dislocated his shoulder in the process, the injury a major blow with Tests to come against Japan, New Zealand and South Africa on successive weekends this month.
"It's always a blow to lose any player. But losing Jac, he was outstanding out there. The try he scored was unbelievable from that distance. It's a blow," Tandy said.
"He dislocated his shoulder. He's probably going to be no good for the rest of the autumn. He's devastated. Ultimately, it's just about Jac recovering. With that, it gives someone else an opportunity."
Wales brought on returning British & Irish Lion Louis Rees-Zammit in the second half for his first Test in two years after his break to try American Football, but it was Argentina who scored a sixth try as Prisciantelli intercepted.
In the last six minutes, Wales showed some fortitude with a consolation try for Murray, but he will have plenty to fix with Japan, New Zealand and South Africa to play over the next three weekends.
Argentine substitute Grondona emphasised their superiority with a try on the final whistle to hand them their biggest victory over Wales.
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