'Terra Nova', the new TV sci-fi epic starring Irish actor Jason O'Mara, has been pushed back in the US schedules.

Deadline reports that a two-hour preview had been scheduled to air in America in May followed by the full series in the autumn.

But the preview has been removed from the May schedule and the series will now premiere in the autumn, because more time is needed to work on the special effects.

Kevin Reilly, Entertainment President at US network Fox, said: "'Terra Nova' is one of the most ambitious television series ever produced.

"The cutting-edge visual effects used to create the world of 'Terra Nova', which is of massive scope and scale, require more time to be realised.

"This aspect of the series is essential, so we are pushing back the special early preview date to give the visual effects team the time needed for their ground-breaking work."

'Terra Nova' follows the adventures of Jim Shannon (O'Mara) and his family who travel back to prehistoric earth as part of an experiment to save the human race.

This is the second delay for the series: Originally, 'Terra Nova' had been due to premiere in the middle of the 2010-11 TV season, but was then delayed until October and the special May preview was scheduled instead.