The NFL ruled that the Cowboys "failed to follow the proper procedures last Friday after quarterback Troy Aikman injured his thumb during practice."
The Cowboys are believed to be the first team ever fined for an injury report violation, director of communications Greg Aiello said.
Aikman hurt the thumb on his passing hand when he hit it on safety Darren Studstill's helmet near the end of Friday's practice. The Cowboys did not notify the league nor the media of the injury despite the fact Aikman required X-rays and extensive treatments Friday and Saturday.
The NFL requires injury disclosures because it is concerned about gamblers getting secret information. The league asks teams to "pay particular attention to key players, such as quarterbacks."
Jones said: "The rule says that 'probable' means a player is a virtual certainty to be available, and that was not the case. Troy was certain to play in the game. . . . If we reported every bruise of that nature and those circumstances, we'd have to basically report every player on our team."