Adnanians are said to be descended from Adnan, a legendary ancestor who is traced back to Ishmael, the son of Abraham. They are predominantly found in the northern and central regions of the Arabian Peninsula, including present-day Saudi Arabia, Jordan, Syria, and Iraq. Some of the well-known Adnanite tribes include the Quraysh, the tribe of the Prophet Muhammad, as well as the Banu Tamim, Banu Anazzah, and Banu Bakr.
Qahtanians, on the other hand, are said to be descended from Qahtan, another legendary ancestor who is believed to have come to the Arabian Peninsula from Yemen. They are primarily concentrated in the southern regions of the Arabian Peninsula, including present-day Yemen and Oman. Some prominent Qahtani tribes include the Himyar, the ancient rulers of Yemen, as well as the Banu Azd, Banu Kindah, and Banu Madhhij.
It's important to note that these subdivisions are based on traditional oral histories and legends, and there is no clear historical or genetic evidence to support a strict dichotomy between Adnanians and Qahtanians. Over time, there has been significant intermingling and assimilation between different Arab tribes, and the distinctions between them have become less pronounced.
Today, the terms "Adnani" and "Qahtani" are often used in a cultural rather than a genealogical sense, referring to the cultural heritage and regional affiliations of different Arab communities.