* Starc takes four late wickets with second new ball to finish with 6-72
* Ackerman and Markram put on 158 for first wicket before South Africa collapse
* Smith ruled out with neck injury, Cummins again chooses to field
Marques Ackerman scored a career-best 95 for South Africa and Australia fast bowler Mitchell Starc took 6-72 as the hosts were bowled out for 329 on a seesaw first day of the decisive third Test at Newlands on Tuesday.
Australia will bat on the second morning after Starc ran through the South African tail with the new ball and the home side let a commanding position slip.
Australia were dealt a blow before play started when key batter Steve Smith was ruled out due to a neck injury on the ground where he was involved in the infamous Sandpapergate scandal in 2018.
For the third time in the series, Australia captain Pat Cummins won the toss and chose to field, only the 12th time a team has done so in Tests at Newlands since 1889.
At the time it looked an odd decision, even more so after South Africa made an excellent start.
"We probably expected more out of the wicket, it was not our best start and South Africa took advantage," Starc told reporters.
"(The wicket) was quite slow, with a tennis ball type bounce. We had to reassess at lunch, problem solve and find a way to be effective. The last two sessions for us went well.
"At one point we thought we would have to bowl a fair bit tomorrow, so to get them out today is good."
QUICK START
The home side were fast out the blocks as Ackerman and Aiden Markram put on 158 in 31.4 overs for the first wicket in a display of attacking intent.
Approaching his maiden century in his second Test, however, Ackerman had a rush of blood to the head as he charged down the wicket at spinner Nathan Lyon (2-71) and was stumped.
It was not only a rash shot that denied him a century, but the catalyst for a collapse as South Africa lost six wickets for the addition of 74 runs, several to poor shots.
Markram (78) and David Bedingham (50) were caught on the boundary attempting pulls, and Wiaan Mulder was caught behind by wicketkeeper Alex Carey playing the same shot as Australia employed an effective short-ball plan.
Ryan Rickelton (42) and Marco Jansen (52) put on 95 for the seventh wicket to edge South Africa ahead again before both were removed in the same over by Starc.
He also took the wickets of Gerald Coetzee and Kagiso Rabada to end the innings just before the scheduled close of play.
The series is level at 1-1 after Australia won the first Test by 214 runs in Durban and South Africa responded with a victory by an innings and 31 runs in Gqeberha.
The team who win the match will occupy the number one position in the test world rankings, a position currently held by Australia.
BRIEF SCORES
South Africa 329 (Ackerman 95, Markram 78, Jansen 52, Starc 6-72, Lyon 2-71) vs Australia