Ecology and Behaviour of Mesozoic Reptiles by John L. Cloudsley-Thompson download in ePub, pdf, iPad
Their jaws were very long and beset with rows of strong conical teeth. The general shape of the body was within the optimal range to minimise drag and for efficient swimming.
Alongside these were various types of ginkgo, pine-like taxodiums, and huge sequoias. Among the former were the Choristodera, a strange assembly of crocodile-like reptiles that diverged from the main diapsid line during the Lower Cretaceous period, some mya. Land-dwelling vertebrates did not turn to life in the sea until the Triassic period, but this trend has been repeated several times since then. Lateral lines contain sense organs that respond to pressure and thus enable their owners to detect nearby moving objects.
Its short neck and toes were primitive features. The object of the present book is to clothe these skeletons with flesh, and to show something of the ways in which their possessors lived. Like insects and birds whose eggs are also laid on land, reptiles eliminate nitrogenous waste in the form of insoluble uric acid. Although there were arid times and regions, much of the land surface was in many ways similar to that of the Amazon valley of today, with vast swamps and rainforests. Like modern varanid lizards and in common with many other reptiles both living and extinct, the mosasaurs probably used their long, whip-like tails to great effect in defence.
Nearly all the individual orders became established during the Triassic, but most of them only reached their maximum development in the Jurassic and Cretaceous periods. By that time, a number of clues had been provided that helped to explain the mystery.
Only a number of ammonoids and some brachiopods seem to have disappeared, however, which is surprising because a major phase of glaciation began then. Their paddle-shaped limbs and feet were strong, their necks long and flexible, and their nostrils had moved slightly backwards from their snouts.
The skull of the placodonts was short and the nostrils had retreated to a position immediately anterior to the eyes. About mya, during the Late Triassic and Early Jurassic, the continental plates of Laurasia and Gondwanaland were united. Smaller, elongated marine reptiles, they existed contemporaneously with the placodonts and early ichthyosaurs, reaching the peak of their development in Late Triassic times. Increase in size followed quickly after the reptiles began to radiate on land.
These shortly led to the three main divisions of reptiles, the anapsids, diapsids and synapsids, characterised by the temporal openings or fenestrae in their skulls Fig. Most of the pelycosaurs were small- to medium-sized insectivores and carnivores with strong skulls and sharp teeth. The latter were an odd collection of possibly unrelated Permian and Triassic reptiles, some lizard-like in appearance, others with small limbs, elongated bodies, and extremely long necks. They swam with the aid of flattened bodies and fish-like tails. Some of the former were quite large.
The whole tail is essentially a shortened continuation of such units. Its powerful jaws were narrow and elongated, the sharp teeth interlocking when the mouth was closed. Were any needed, this distribution provides unequivocal evidence for continental drift. Some of the land-living reptiles were shore-dwelling but semi-aquatic or amphibious forms that spent some parts of the day on land and some in water as modern crocodilians do. No doubt the four types of locomotion found in extant crocodiles were present in these ancestral forms.
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