منابع مشابه
Fossil embryos deep in the fossil record
Embryos have been found in ‘old’ rocks on four continents, especially in Siberia, Nevada, Australia and China. They have been discovered in sedimentary rocks of even Late Neoproterozoic age, assuming the evolutionary geological column1 (figure 1). The Neoproterozoic is the period, so called, between 1 billion and 550 million years ago. This discovery was in the Doushantuo Formation, Guizhou Pro...
متن کاملFossil DNA
Also known as... ancient DNA. The New Shorter Oxford Dictionary offers the precise explanation of ‘ancient’ as ‘belonging or pertaining to the period before the fall of the Western Roman Empire in AD 476.’ DNA can be recovered from fossils much older than 1500 years, but the inevitable time-dependent decay of the DNA structure due to oxidation and hydrolysis makes retrieval increasingly difficu...
متن کاملFossil spiders.
Over the last three decades, the fossil record of spiders has increased from being previously biased towards Tertiary ambers and a few dubious earlier records, to one which reveals a much greater diversity in the Mesozoic, with many of the modern families present in that era, and with clearer evidence of the evolutionary history of the group. We here record the history of palaeoarachnology and ...
متن کاملPicking buttercups and eating butter cups: spelling alternations, semantic relatedness and their consequences for compound processing
Semantic transparency (ST) is a measure quantifying the strength of meaning association between a compound word (buttercup) and its constituents (butter, cup). Borrowing ideas from computational semantics, we characterize ST in terms of the degree to which a compound and its constituents tend to share the same contexts in everyday usage, and we collect separate measures for different orthograph...
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ژورنال
عنوان ژورنال: Nature
سال: 1922
ISSN: 0028-0836,1476-4687
DOI: 10.1038/109136a0