Consisting of two parchment leaves, the manuscript in Birmingham contains parts of what are now Chapters 18 to 20. For years, the manuscript had been mistakenly bound with leaves of a similar Quran manuscript.

Saud al-Sarhan, the director of research at the King Faisal Center for Research and Islamic Studies in Riyadh, Saudi Arabia, said he doubted that the manuscript found in Birmingham was as old as the researchers claimed, noting that its Arabic script included dots and separated chapters — features that were introduced later. He also said that dating the skin on which the text was written did not prove when it was written. Manuscript skins were sometimes washed clean and reused later, he said.

Professor Thomas said the text of the two folio pages studied by Ms. Fedeli, who received her doctorate this month, corresponded closely to the text of the modern Quran. But he cautioned that the manuscript was only a small portion of the Quran and therefore did not offer conclusive proof.

Omid Safi, the director of the Duke Islamic Studies Center and the author of “Memories of Muhammad: Why the Prophet Matters,” said that the discovery of the manuscript provided “further evidence for the position of the classical Islamic tradition that the Quran as it exists today is a seventh-century document.”

The manuscript is in Hijazi script, an early form of written Arabic, and researchers said the fragments could be among the earliest textual evidence of the holy book known to survive.

A manuscript from the University of Tübingen Library in Germany was found last year and sourced to the seventh century, 20 to 40 years after the death of the prophet. Fragments from Tübingen were radiocarbon-tested by a lab in Zurich and determined with 95 percent certainty to have originated from 649 to 675, making the Birmingham text a few years older.

Radiocarbon dating measures levels of a heavier form of carbon as it appears in the atmosphere over time and becomes part of plants and, later, the animals that eat them. In this case, the Oxford laboratory measured the age of the goat or sheep whose skin was turned into parchment.