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991.
Danita S. Brandt 《Alcheringa: An Australasian Journal of Paleontology》2013,37(3):399-421
A comparison of ecdysial patterns between trilobites and other macrobenthic marine arthropods (crabs, shrimp, lobsters, horseshoe crabs) reveals differences that may have evolutionary consequences. Limulus and many malacostracans apparently have a signature ecdysial style; conversely, a range of moult configurations characterized trilobite ecdysis, and this variation is evident even within individual species. A canalised ecdysial habit may be safer or metabolically more efficient and therefore, summed over the history of the class, evolutionarily advantageous. Some trilobite clades show evolutionary trends toward morphologies that would have facilitated ecdysis (e.g. reduction in the number of thoracic segments, reduction in the number and prominence of spines), but co-adaptation or multiple-use effects complicate the evolutionary signal of ecdysial selection. Survivorship analysis supports a possible link between ecdysial habit and evolutionary success: genera with fewer thoracic segments (= easier ecydsis) are longer-lived. The increased predation pressure on trilobites through the Palaeozoic would have amplified the evolutionary impact of an inefficient moult habit. The cumulative effects of a less-than-optimal ecdysial habit, and a physiology that apparently required reconstituting a calcitic exoskeleton de novo with each moult, are compelling biotic factors to consider in examining functional interpretations, life histories, evolutionary trends, and ultimate disposition of the Trilobita. 相似文献
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JACQUES OMNÈS 《Oxford Journal of Archaeology》1983,2(3):253-263
Summary. The parietal art in the cave of Labastide was discovered in 1932 by Norbert Casteret, the spelaeologist, but another 50 years were to pass before an exhaustive inventory was made of these figures, followed by their publication. The study of the parietal art has revealed a sanctuary with a predetermined layout in which the main panels were specially devoted to large figures representing a central Bison-Horse theme. The cave is also of interest because of the discovery of traces of 'Magdalenian IV' occupation (14,260 b.p.): about twenty small, engraved stone slabs display stylistic analogies with the parietal art, and are the best means of dating it. 相似文献
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