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Re: The Cretaceous Middle East



An interesting question is: What scenario might be at least reasonably
credible for survival of dinosaurs in Yemen up to the present?

How about this: 

We know that freshwater biota were less affected than others by the K/T
extinctions. Suppose that a river/lake-living dinosaur evolved in the Late
Cretaceous of Africa (it might have been a hippo or crocodile or otter or
capybara or even river-dolphin analog). This survived the Chicxulub impact
somewhere in NE Africa and evolved/diversified modestly in the Paleogene,
but never spread widely since it could (would) not move long distances
overland between river systems. This might well have avoided notice by
palaeontologists since Africa's Paleogene vertebrate fossil record is very
bad. During the Neogene these surviving dinosaurs were outcompeted by
hippos or whatever (alternatively they might not have survived the
widespread volcanism, mountain-building and rifting (and disruption of
river systems) that created the Great Rift Valley and the Ethiopian
highlands). However, part of a river system was truncated by the opening of
the Red Sea and still survives as a ground-water fed lake, complete with
(small) dinosaurs, in a valley in Yemen. 

There are some analogs for this scenario, the Australian Lungfish (whih is
older than the dinosaurs) apparently only survived in a single very limited
river system in Queensland when discovered (this is a bit uncertain due to
early translocations) and crocodiles survive in a few amazingly small
fresh-water pools in Sahara (admittedly only for 5-10,000 years, but
still). As for the surviving lake, most of the salt lakes in West Australia
are fragments of an old river system, at least parts of which dates back to
the times before Australia separated from Antarctica. Admittedly they have
all been dry for much of the last several million years, but there is a
fair number of species of African extraction in the mountains of southern
Arabia which shows that the area has never been completely arid, even at
glacial maximums.

Tommy Tyrberg