Milestones from the younger side of 40

Though the majority of the Academy Award nominees in the major categories are 40 and older -- in fact, supporting actress nominee Ruby Dee is 83 and supporting actor nominee Hal Holbrook is 82 -- there are several who haven’t hit their fourth decade. Of those, only Paul Thomas Anderson, 37, is a previous nominee in the original screenplay category (for 1997’s “Boogie Nights” and 1999’s “Magnolia”). This year, he’s a first-time nominee in the adapted screenplay, director and best picture contests for his Daniel Day-Lewis starrer, “There Will Be Blood.” Here’s a look at the rest of the field of younger hopefuls celebrating their first nominations.

-- Susan King

Casey Affleck

Age: 32

Back story: Baby brother of Ben Affleck, who directed his sibling in last year’s “Gone Baby Gone,” he’s best known as one of the gang of thieves in the “Ocean’s Eleven” films.

Nominated for:

Supporting actor (“The Assassination of Jesse James by the Coward Robert Ford”)

Noteworthy: Affleck received the best reviews of his career for his turn as Ford, a young man with dreams of becoming an outlaw who gains notoriety after he murders the legendary bandit.

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Diablo Cody

Age: 29

Back story: Cody got a media studies degree from the University of Iowa and came to fame after she chronicled her yearlong stint working in strip clubs and peep shows in Minneapolis in her 2006 memoir, “Candy Girl: A Year in the Life of an Unlikely Stripper.”

Nominated for:

Original screenplay (“Juno”)

Noteworthy: Strike or no strike, Cody’s enjoyed something of a charmed awards season run, with a raft of nominations and prizes from the Writers Guild of America and BAFTA for her script about a pregnant teen.

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Marion Cotillard

Age: 32

Back story: Cotillard began acting onstage in France as a child and scored her first major film success with the 1998 Luc Besson production “Taxi.” Her credits include “A Very Long Engagement” and “Big Fish.”

Nominated for:

Actress (“La Vie en Rose”)

Noteworthy: Cotillard’s depiction of French singer Edith Piaf required her to undergo a physical transformation and to study the mannerisms of the woman known as “the little sparrow.”

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Ellen Page

Age: 20

Back story: The diminutive Canadian began acting at age 10, but she first garnered critical acclaim for her role in the controversial 2005 indie “Hard Candy.”

Nominated for:

Actress (“Juno”)

Noteworthy: “Juno” is arguably Page’s lightest indie. She’s played a murderous adolescent in “Hard Candy,” a street urchin seduced by a nomadic cult in the Canadian release “Mouth to Mouth,” a mentally ill girl wandering the streets naked in “The Tracey Fragments,” and a brutalized victim in “An American Crime.”

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Sarah Polley

Age: 29

Back story: The Canadian debuted in the 1985 Disney film “One Magic Christmas.” Polley made the transition from child to adult star in such films as “The Sweet Hereafter.”

Nominated for:

Adapted screenplay (“Away From Her”)

Noteworthy Praise for Polley, and Oscar momentum for “Away From Her,” began with the film’s debut at Sundance in 2007, where critics including The Times’ Kenneth Turan singled her out as a director to watch.

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Jason Reitman

Age: 30

Back story: Yet another Canadian, the filmmaker is the eldest child of director Ivan Reitman. He began working as a production assistant on his dad’s films and segued into shorts in the 1990s.

Nominated for: Director (“Juno”)

Noteworthy: Reitman’s first feature film as director was the 2006 indie hit “Thank You for Smoking.”

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Saorise Ronan

Age: 13

Back story: Ronan began acting on TV series in her native Ireland, and the first feature film she ever shot, “Death Defying Acts,” will be released this year.

Nominated for: Supporting actress (“Atonement”)

Noteworthy: Ronan has managed to scoop up a raft of the most desired children’s parts. In the coming year, she will star opposite Bill Murray in “City of Ember” and portray 14-year-old Susie Salmon in Peter Jackson’s upcoming screen version of “The Lovely Bones.”

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Amy Ryan

Age: 39

Back story: The two-time Tony-nominated theater veteran has appeared in such TV series as “The Wire” and movies as “Before the Devil Knows You’re Dead” and “Keane.”

Nominated for:

Supporting actress (“Gone Baby Gone”)

Noteworthy: Ryan follows her performance as the drug-addled mother of a kidnapped 4-year-old from South Boston with roles in Clint Eastwood’s “The Changeling” and Paul Greengrass’ “The Imperial Life in the Emerald City.”

-- Gina Piccalo and Rachel Abramowitz contributed to this report