نتایج جستجو برای: middle ordovician
تعداد نتایج: 156546 فیلتر نتایج به سال:
Establishing the timescale of early land plant evolution is essential for testing hypotheses on the coevolution of land plants and Earth's System. The sparseness of early land plant megafossils and stratigraphic controls on their distribution make the fossil record an unreliable guide, leaving only the molecular clock. However, the application of molecular clock methodology is challenged by the...
This report of a severely injured trilobite from the Middle Ordovician (~465 Ma) accords with a number of similar observations of healed lesions observed in trilobites. The uniqueness of the specimen described here is that the character of the repair-mechanisms is reflected by the secondarily built structures, which form the new surface of the ruptured compound eye. Smooth, repaired areas insid...
Phylogenetic studies are rare in early Palaeozoic cephalopods. Here, we present the first cladistic analysis of order Lituitida based on published, as well some new, material. Three clades recovered within ingroup lituitids, Sinoceras, Ancistroceras and Lituites; former two groups correspond to family Sinoceratidae, latter one Lituitidae. The topology shows that Sinoceratidae represents basal b...
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