Scarlets scale the summit
The 22-20 nail-biting victory at Benetton Treviso saw them take the lead in the Pro12 competition.
Sam Christie struck the first blow for Treviso, but Scarlets responded through Allen, whose Scarlets bow was delayed by a bicep injury, and DTH van der Merwe tries.
Jayden Hayward – who was denied five points off the tee by the post – nailed a penalty to see Treviso in at half-time two points behind, but Scarlets No.8 Allen rumbled over again early in the second half.
Treviso roared back, Edoardo Gori crossing before Christie completed his try-double – which Hayden could not convert – to put the hosts one point ahead, but replacement Shinger's last-ditch penalty bailed out Scarlets.
This was an opportunity for Scarlets to ascend to the top of the Pro12 tree after Connacht's slip up at Cardiff Blues on Friday night.
But though Treviso were on a 15-game losing streak in the league, the Italians made it known from the outset that a win at the Stadio Monigo was not going to come easy.
Hayward hit the woodwork with a penalty in the fourth minute after some early Treviso momentum at the scrum.
But hardly a minute later, the Kiwi fly-half burst through Scarlets' line and Christie was on hand to eventually cross over in the corner.
Hayward added the extras but conceding seemed to wake Wayne Pivac's men up and Aled Thomas kicked to the corner after an under-pressure Treviso infringed.
And Allen restored parity as he rumbled over the line, despite the attention of multiple defenders. Thomas converted.
Scarlets looked the more likely heading into the second quarter with, Aled Davies, Steff Evans and DTH van der Merwe all threatening to find another gear.
The visitors did have to repel Treviso however – winning a penalty camped on their own line – before van der Merwe notched their second try.
The Canadian flyer was on the end of a flowing move from right to left after receiving a Rob Evans miss pass to race across unopposed in the 27th minutes, though Thomas' conversion drifted wide.
Treviso were far from deflated and thought they had responded when lock Jean-Francois Montauriol plunged over, but the TMO adjudged he had been held up.
The Italians did get some reward for their efforts before the half was out, Hayward slotting a penalty to reduce the deficit down to two.
Five minutes after the break Treviso managed to create a huge overlap on the right-hand side, but Edoardo Gori's final pass was forward – denying Enrico Bacchin an easy try.
They were made to regret it on 52 minutes as Scarlets pulled further ahead through Allen, the No.8 continuing his fine first impression by barging across following a close-quarters scrum.
Scarlets could now afford to have half an eye on the bonus point, but Treviso were not going away and Gori collected a loose ball before surging over the line on the hour.
Hayward again hit the uprights with the conversion before Treviso hit the front in the 71st minute.
After Scarlets were pinged for not releasing, Treviso formed a maul from the line-out – and with most of the defenders tied up, the ball was flung out to Christie who did the rest.
Hayward missed the tricky conversion and four minutes from time, Treviso were penalised for going offside to hand Shingler his match-winning chance.
The scorers:
For Benetton Treviso:
Tries: Christie 2, Gori
Con: Hayward
Pen: Hayward
For Scarlets:
Tries: Allen 2, Van der Merwe
Cons: Thomas 2
Pen: Shingler
Teams:
Benetton Treviso: 15 Luke McLean, 14 Andrea Pratichetti, 13 Tommaso Iannone, 12 Sam Christie, 11 Edoardo Gori, 10 Jayden Hayward, 9 Chris Smylie, 8 Dean Budd, 7 Alessandro Zanni (captain), 6 Francesco Minto, 5 Jeff Montauriol, 4 Teofilo Paulo, 3 Filippo Filippetto, 2 Ornel Gega, 1 Matteo Zanusso.
Replacements: 16 Roberto Santamaria, 17 Alberto De Marchi, 18 Simone Ferrari, 19 Tom Palmer, 20 Marco Barbini, 21 James Ambrosini, 22 Enrico Bacchin, 23 Simone Ragusi.
Scarlets: 15 Steff Evans, 14 Michael Tagicakibau, 13 Regan King, 12 Hadleigh Parkes, 11 DTH van der Merwe, 10 Aled Thomas, 9 Aled Davies, 8 Morgan Allen, 7 John Barclay (captain), 6 Aaron Shingler, 5 Lewis Rawlins, 4 Jake Ball, 3 Samson Lee, 2 Emyr Phillips, 1 Rob Evans.
Replacements: 16 Kirby Myhill, 17 Dylan Evans, 18 Rhodri Jones, 19 Tom Price, 20 Maselino Paulino, 21 Rhodri Williams, 22 Steve Shingler, 23 Gareth Owen.
Referee: Dudley Phillips (Ireland)
Assistant referees: Giuseppe Vivarini (Italy), Simone Boaretto (Italy)
TMO: Carlo Damasco (Italy)
Source: @PRO12rugby