Article: Haruspicy was also used in public cult, under the supervision of the augur or presiding magistrate. The haruspices divined the will of the gods through examination of entrails after sacrifice, particularly the liver. They also interpreted omens, prodigies and portents, and formulated their expiation. Most Roman authors describe haruspicy as an ancient, ethnically Etruscan "outsider" religious profession, separate from Rome's internal and largely unpaid priestly hierarchy, essential but never quite respectable. During the mid-to-late Republic, the reformist Gaius Gracchus, the populist politician-general Gaius Marius and his antagonist Sulla, and the "notorious Verres" justified their very different policies by the divinely inspired utterances of private diviners. The senate and armies used the public haruspices: at some time during the late Republic, the Senate decreed that Roman boys of noble family be sent to Etruria for training in haruspicy and divination. Being of independent means, they would be better motivated to maintain a pure, religious practice for the public good. The motives of private haruspices especially females and their clients were officially suspect: none of this seems to have troubled Marius, who employed a Syrian prophetess.

Question: Which of the entrails was especially important to augury?
liver