Toarcian and Bajocian ammonites from the Haushi-Huqf Massif of southwestern Oman and the Hawasina Nappes of the Oman Mountains: Implications for paleoecology and paleobiogeography

New and rare Jurassic ammonites have been found in Oman. A latest Bajocian Arabian Platform-type species was discovered in the Haushi-Huqf Massif autochthon of southwestern Oman, and Bajocian species typical of the Mediterranean Tethys and northwestern Europe were found in the Kawr-Misfah exotic unit of the Hawasina Nappes in the Oman Mountains. The dates provided by the new fauna have resulted in a reinterpretation of the geologic history of the containing rocks, and of their paleoecology and paleobiogeography. It is significant that ammonites from shallow-marine environments of the Arabian Platform are in close proximity to species from open-sea environments of the Mediterranean Tethys and northwestern Europe. This shows that endemism of the Arabian Province resulted from ecological isolation, whereas open-marine environments on the Oman margin, especially the pelagic seamounts off the margin, form part of a migration route between western and eastern Tethys (or Indo-Southwest Pacific), and perhaps far beyond. The occurrences among the Tethyan and pandemic components of ammonite faunas in the Canadian Pacific Cordillera of most of the taxa of the open-marine environments on the Oman margin reopens the question of Pacific biogeography during the Early Jurassic before the Hispanic oceanic corridor was completely open. Among the proposed models, the Pantropic Distribution Model of Newton is examined in the light of the Cretaceous paleobiogeography, with particular reference to rudists.