Replacements: Rory Harrison, Adam Clarkin, Michael Cawley, James Thornton, Dan Costello.
Replacements: Cathal O'Flynn, Tom Byrne, Keith Donohoe, Peter du Toit, Conor Keegan.
Second half tries from Niall Earls and James Murray had left 'Tarf in a perilous position, but courtesy of David Joyce's injury-time time they still lead the Division 1A table by the slenderest of margins.
Buoyed by their crucial victory over chief challengers Old Belvedere in last weekend's Friday Night Lights encounter, the north Dubliners began today's game with a great deal of intent.
Nonetheless, a third-placed finish is still within their grasp and UCD were hoping to upset the apple cart.
Against the run of play, the students broke the deadlock in spectacular fashion just five minutes in.
Barry Daly received the ball on the left wing and with a neat sidestep, he evaded the normally watertight 'Tarf rearguard to race through unopposed for the opening try.
Full-back Earls, who had been switched from his customary out-half role in the absence of Tom Fletcher, converted with aplomb and despite making a positive start to the proceedings, the visitors found themselves with an early deficit to overcome.
An expertly-converted Joyce penalty eight minutes in did offer Clontarf some relief, but a brace of Earls place-kicks helped UCD to open up a ten-point advantage by the 23rd minute.
Considering the absentees from the students' line-up, this was a very impressive performance by Shane Grannell and company.
However, at the end of a series of five-metre scrums for Andy Wood's men, scrum half Sam Cronin released the ball to lively full-back Timmy McCoy who dived over bravely for a much-needed five-pointer.
An excellent Joyce conversion reduced the gap to three (13-10), but just when it looked like the table toppers were ready to turn the game on its head, UCD once again responded.
On the half hour mark, number 8 Eoin Joyce was halted just shy of the try-line from his surging run. He managed to offload to inside centre Shane O'Meara, who eventually squeezed over on the left hand side for a converted score.
This was another hammer blow for 'Tarf and although Joyce added his second penalty two minutes before the interval, the sin-binning of McCoy in the 33rd minute left the Castle Avenue outfit exposed in defence, and Stephen Murphy took full advantage with a terrific try deep into stoppage time.
Another majestic kick by Earls ensured that UCD brought a 27-13 advantage into the interval.
This was a substantial cushion for Bobby Byrne's youngsters but with 40 minutes still to play, 'Tarf were not out of contention just yet.
Another three-pointer from Joyce, 55 minutes in, did give them something to work towards.
They could not quite take advantage of some promising moves in the early stages after the restart though and whenever UCD broke from deep, they looked like they were capable of adding to their already considerable tally.
Having gone close to breaking through via O'Meara and Liam Bourke on the right wing, the play was switched out to the left where a succession of lay-offs provided the platform for a seven-point salvo from Earls on the hour mark.
This fourth try meant that UCD were guaranteed to emerge with a bonus point and when James Murray finished off a superb team move from the next attack, a ninth league success appeared inevitable for the home team.
Time was running out for Clontarf as they aimed to gain some form of consolation from this game but after Michael McGrath darted in under the posts 15 minutes from the end, there was still time for them to swing the pendulum in their direction.
The introduction of O'Flynn, Peter du Toit and Conor Keegan certainly added an extra dimension to their play.
A pushover score from O'Flynn five minutes from time may well be the most important five-pointer they will get all season.
For a third time on the day, Joyce's conversion was slotted between the posts and though UCD seemed to have weathered the storm successfully, the dependable Ireland Club international added an 85th minute penalty to give his side a slender hold at the top of the table.
Referee: Kieran Barry (IRFU)