First documented record of the ammonite Turrilites costatus LAMARCK, 1801 from the Cenomanian of northern Saudi Arabia: Implications for Arabian Plate paleogeography

ABDULLAH HOMOUD ALRWAILI

This study presents the first documented occurrence of the heteromorph ammonite genus Turrilites LAMARCK, 1801, from the Cretaceous strata of the Kingdom of Saudi Arabia. In-situ fossil assemblages, identified as Turrilites costatus LAMARCK, 1801, were discovered and documented in three separate outcrops of the Aruma Formation, located south of the city of Ar'ar in northern Saudi Arabia. The geographic distribution of these localities spans a distance of over 30 kilometers, suggesting a regional phenomenon rather than an isolated anomaly.

Historically, the published record of this genus on the Arabian Peninsula has been restricted to the Natih Formation of Oman, on the southeastern margin of the Arabian Plate. The presence of Turrilites, a well-established index fossil for open-marine, outer-shelf environments, in the interior of the Arabian Plate presents new paleontological data. These findings suggest the possibility that environmental conditions in the northern plate interior during the Cenomanian were more conducive to open marine connections than previously thought. This discovery proposes a need for a reassessment of the region's paleogeographic models and supports the hypothesis of an open seaway connected to the Neo-Tethys Ocean.