The hosts sat four points clear at the summit at the start of the day, but their title challengers ran in eight tries on the 3G pitch at the Ystrad Mynach Centre for Sporting Excellence to draw level with them on 49 points.
Bwl flyer Joe Williams kicked off the try-fest before the Pitmen battled back with a converted score from Jonny Wright. But Alex Taylor crossed for the visitors to retake the lead, and they never looked back.
A penalty try soon followed before Gareth King and Ricky Thomas went over for a 29-7 advantage. Lewis Barnett got one back for Penallta, but Dale Stuckey crossed for a quick-fire double before Cory James rounded off the scoring.
Ammanford were able to claw back a point on runaway SSE Swalec Division 1 West Central leaders Skewen as they picked up a bonus point in their 32-10 home win over Kenfig Hill.
They were 24-0 ahead at the break before going on to secure the full five points to cut the gap at the top of the table to 14 points with two games in hand. Meanwhile, Skewen secured their 13th win of the season with a 25-10 home triumph over Ystalyfera.
But there were only three tries from Scrum-half James Ball, James Pallett and wing Matthew Billet for the league leaders as they fell short of their bonus point target.
A Lee Evans inspired Waunarlwydd toppled SSE Swlaec Division 1 West table-toppers Felinfoel 14-9. The full-back crossed for a try and converted both of his side’s scores to put the fourth placed side right back in the title race.
Aled Roberts landed three penalties for Felinfoel, but that could not prevent Dunvant from leap-frogging them at the top of the table.
In Division 1 North, league leaders Nant Conwy made the most of closest rivals Pwllheli having an afternoon off as they plundered a bonus point win at home against Llangefni. Their 57-0 triumph moved them nine points clear of Pwllheli at the top.
Caernarfon’s 22-0 home win over Dolgellau ensured they closed the gap to two points on second place, while COBRA picked up a bonus point with their 40-5 home win over Llandudno. Bala won 18-10 at Mold, while Abergele were 20-16 winners at home over Ruthin.
