Palaeontology or a Systematic Summary of Extinct Animals and Their Geological Relations

Palaeontology or a Systematic Summary of Extinct Animals and Their Geological Relations

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1861 edition. Excerpt: ...tenuirostris with those of the gangetic Gharrial, an equal degree of strength and of alveolar border for teeth result from two very different proportions in which the maxillary and premaxillary bones are combined together to form the upper jaw. The prolongation of the snout has evidently no relation to this difference; and we are accordingly led to look for some other explanation of the disproportionate development of the premaxillaries in Q the Ichthg/osaums. It appears to me to give additional proof of the collective tendency of the affinities of the I chthyosawas to the labyrinthodont and lacertian types of structure. The backward or antorbital position of the nostrils, like that in whales, is related to their marine existence. But in the Labyrinthodonts and Lacertians, the nostrils being nearer the fore part of the head, their anterior boundaries are formed by the premaxillaries; it appears, therefore, to be in conformity with the above-mentioned affinities, that the premaxillaries of the Ichthyosaur should still enter into the same relation with the nostrils, although this involves an extent of anterior development proportionate to the length of the jaws, the forward production of which sharp-toothed instruments fitted them, as in the modern dolphins, for the prehension of agile fishes. That the Ichthyosaurs occasionally sought the shore, crawled on the strand, and basked in the sunshine, may be inferred from the bony structure connected with their fore fins, which does not exist in any porpoise, dolphin, grampus, or whale; and for want of which, chiefly, those warm-blooded, air-breathing, marine animals are so helpless when left high and dry on the sands. The structure in question in the Ichthyosaur is a strong osseous arch, more

Product details

  • Paperback
  • 188.98 x 246.13 x 7.11mm | 249.47g
  • English
  • Illustrations, black and white
  • 1236946952
  • 9781236946959