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the top predators and thus changed prey-predator relationships. Micropaleontological
analyses of Late Maastrichtian pelagic sediments detect short-term paleotemperature
fluctuations (Li & Keller, 1998). A progressive cooling trend between ~66.8-65.45 Myr was
followed by rapid extreme warming 400-200 Kyr before the end of the Maastrichtian, which
was succeeded by a cooler climate during the last 100 Kyr of this stage (Abramovich &
Keller, 2002; Abramovich et al., 2010).
4. Victims of disturbed prey-predator relationships under climatic and
ecological instability
Despite the overall flourishing of the Upper Cretaceous marine fauna and flora, the local
balance of prey-predator relationship was very fragile, threatening this global paradise.
Optimal living conditions on land increased animal diversity, populations size and the
dimensions of individuals (gigantism), as in the marine environments. However, any
temporary ecological disturbance might have reduced reproduction, resulting in much less
young, which played a significant role in the food-chain. The further collapse of the food
chain, as the result of increased predatory stress, is examined herein, by comparing the
affinities of the organisms which became extinct at the end of the Cretaceous Period to those
which survived the biological crisis. The present study builds on the detailed analysis of the
geological record of most faunal and floral groups around the K-T boundary, carried out by
a large team of experts (MacLeod et al., 1997). They pointed out the terrestrial and
extraterrestrial factors which affected life on Earth during a long period as well as short-
catastrophic processes close to the K-T boundary. However, the control of the extinction-
survivorship pattern was not defined. Re-evaluation of the characteristics of representative
marine and terrestrial faunal groups will demonstrate that all those which became extinct at
the end of the Cretaceous, were at some stage of their life unable to avoid their predation,
thus being victims of temporary extreme predatory stress. This selective over-predation of
the vulnerable organisms was caused by the collapse of the food chain as the result of
climatic and ecological instability. These are partly reflected by paleotemperature
fluctuations of the oceans surface water and deeper levels (Li & Keller, 1998; Abramovich &
Keller, 2002), as well as reduction in oxygen content in seawater and dwarfing in marine
calcareous planktonic microorganisms. All these phenomena can be related to fluctuations
in the intensity of the volcaniclastic dust screening the sunlight, hence affecting
photosynthetic activity of the flora and disturbing the biological clock of animals in the sea
and on land.
4.1 Vertebrates: Reptiles and fishes
The disappearance of the dinosaurs close to the end of the Cretaceous Period is presented in
scientific and popular publications and films as evidence to the most impressive
catastrophic event in Earth history. These reptiles ruled over the land while their flying
relatives (pterosaurs) and the marine ones (e.g., plesiosaurs and mosasaurs) were the top
predators in the sky and the sea. They diversified during the Late Cretaceous and many of
their species grew to giant dimensions (9-15 m long mosasaurs; 11-12 m wing-span of the
pterosaur
Quetzalcoatlus
). Their apparent simultaneous disappearance from over the whole
world was puzzling. Whatever caused it did not kill the related crocodiles and did not harm
the sensitive frogs and salamanders. This selective elimination of the most skillful predators
resulted from their early ontogenetic stage. Dinosaurs and pterosaurs were oviparous,
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