In the teams’ first Championship meeting since 2007, Glamorgan gave a debut to Abergavenny product Norton in place of concussion victim Jamie McIlroy, while Somerset brought in Jake Ball and Jack Leach for Alfie Ogborne and Thomas Rew, who had A-level commitments.
The well-built Norton had previously played just one One Day Cup match, in which he also took three wickets.
It looked like a good toss to win in cool grey conditions with plenty of grass on the pitch, and James Rew did not last long in his new role, bowled by an excellent nip-backer from Timm van der Gugten.
But Somerset quickly got going with Thomas and Tom Lammonby picking off the odd poor ball to reach 104-1 at lunch.
Thomas stuck it out despite Zain Ul Hassan beating the outside edge repeatedly, then lofted spinner Ben Kellaway for a straight six to bring up his 50 and the team’s 100.
Their stand had reached 133 when both fell in quick succession, Thomas bowled by Australian paceman Ryan Hadley and Lammonby falling lbw for 45, playing no shot to Norton to spark scenes of celebration for his maiden wicket.
Extra bounce from Norton saw Archie Vaughan (17) edge behind the wicket, while Glamorgan thought they had Abell caught at slip by Colin Ingram off Ul Hassan, but the batter stood his ground and had the benefit of the doubt.
Will Smeed, a white-ball veteran, but red-ball rookie, was caught by Ingram off Van der Gugten for 12 as Glamorgan continued to find some life in the green pitch despite the sun coming out.
Craig Overton (33) joined Abell in a stand of 71 before edging Norton to slip, and both Abell and Lewis Gregory nearly played on to the new ball while Gregory was dropped at slip off Van der Gugten.
Abell drove stylishly to keep the scoreboard ticking nicely while Gregory shared in a stand of 66 to tilt the balance further in their side’s favour.
Glamorgan’s bowlers earned late rewards as Abell was caught behind off Ul Hassan from a slightly tired drive, Gregory (37) edged Ul Hassan to slip and Migael Pretorius was also caught behind, off Hadley, from the final ball of the day.
After losing the toss, Somerset will be thankful to have a reasonable total for their bowlers to defend, unless the pitch loses some of its first-day spice.