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The dinosaurs ("terrible lizards") constitute two different groups of extinct reptiles, derived from a common ancestor, and together with other groups like crocodiles, birds and other extinct reptiles, share unique anatomical features.
The dinosaurs appeared on earth during the Triassic period, 235 million years ago, and continued to exist to the end of the Mezosoic (end of the Cretaceous) era, when all of them, 65 million years ago, became extinct together with many other groups of organisms. The common explanation of this mass extinction is probably due to a massive impact of an asteroid with the face of earth, the consequence of which was a world-wide catastrophe to life.
During most of their existence on earth (around 170 million years) the dinosaurs dominated most of the continental habitats, were wide spread all over the continents and fed on a broad spectrum of diets (from feeding on leaves to engaging a ferocious predatory behavior). Some of them became highly socialized, laid eggs in bird-like nests and protected their youngsters. Some others achieved huge dimensions of the body-size.
In the settlement of Beit Zait near Jerusalem, footprints of some dinosaurs were found, which belong to a group of agile animals, running on their hind limbs, while their forelimbs were relatively very small, never used for locomotion but rather helped them to grasp food or prey. The late Prof.. M. Avnimelech from the Hebrew University of Jerualem identified those footprints as belonging to the genus Struthiomymus (=ostrich like). Indeed, the reconstruction of the animal (exhibited in the backyard of the department of Geology in the Hebrew University) shows a close artificial similarity with ostriches and their capability for a highspeed locomotion. Yet, contrary with all otherbirds, its body was covered with horny scales, showed no teeth in its jaws, which was covered with a horny sharp sheath, and fed on leaves. The Belt Zait dinosaur was relatively small (150 kg, 4 meters long).
Related species of the same age were described from North America and Mongolia. Until now no dinosaur bones were found in Israel, but the footprints of Belt Zait show that a band of this species ran about the shoreline of the old Tethys ocean which, at that time, covered the coasts of the Middle East.
Prof. Eitan Tsrenov
The Hebrew University, Jerusalem
