<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>L. Liu</dc:contributor>
  <dc:contributor>David Bukry</dc:contributor>
  <dc:creator>Wuchang Wei</dc:creator>
  <dc:date>1993</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;&amp;nbsp;Type material of calcareous nannofossil index species&amp;nbsp;&lt;/span&gt;&lt;i&gt;Coccolithus crassus&lt;/i&gt;&lt;span&gt;&amp;nbsp;and two geographically widespread species&amp;nbsp;&lt;/span&gt;&lt;i&gt;Toweius magnicrassus&lt;/i&gt;&lt;span&gt;&amp;nbsp;and&amp;nbsp;&lt;/span&gt;&lt;i&gt;T. callosus&lt;/i&gt;&lt;span&gt;&amp;nbsp;have been studied by both light and SEM microscopy and morphometric measurements were made.&amp;nbsp;&lt;/span&gt;&lt;i&gt;Coccolithus crassus&lt;/i&gt;&lt;span&gt;&amp;nbsp;resembles&amp;nbsp;&lt;/span&gt;&lt;i&gt;Coccolithus pelagicus&lt;/i&gt;&lt;span&gt;&amp;nbsp;but has a raised cycle of elements around the centre of the distal shield. It probably evolved from&amp;nbsp;&lt;/span&gt;&lt;i&gt;C. pelagicus.&lt;/i&gt;&lt;span&gt;&amp;nbsp;Both&amp;nbsp;&lt;/span&gt;&lt;i&gt;T. magnicrassus&lt;/i&gt;&lt;span&gt;&amp;nbsp;and&amp;nbsp;&lt;/span&gt;&lt;i&gt;T. callosus&lt;/i&gt;&lt;span&gt;&amp;nbsp;have three cycles of elements in distal view, which is a characteristic of&amp;nbsp;&lt;/span&gt;&lt;i&gt;Toweius. Toweius magnicrassus&lt;/i&gt;&lt;span&gt;&amp;nbsp;is larger than&amp;nbsp;&lt;/span&gt;&lt;i&gt;T. callosus.&lt;/i&gt;&lt;span&gt;&amp;nbsp;Differentiation of&amp;nbsp;&lt;/span&gt;&lt;i&gt;T. magnicrassus&lt;/i&gt;&lt;span&gt;&amp;nbsp;from&amp;nbsp;&lt;/span&gt;&lt;i&gt;T. callosus&lt;/i&gt;&lt;span&gt;&amp;nbsp;is possible and useful because there is generally a size gap between them in a given sample and they have different stratigraphic ranges. However, both&amp;nbsp;&lt;/span&gt;&lt;i&gt;T. callosus&lt;/i&gt;&lt;span&gt;&amp;nbsp;and&amp;nbsp;&lt;/span&gt;&lt;i&gt;T. magnicrassus&lt;/i&gt;&lt;span&gt;&amp;nbsp;appear to increase in size from high to low latitudes.&amp;nbsp;&lt;/span&gt;&lt;i&gt;Toweius callosus&lt;/i&gt;&lt;span&gt;&amp;nbsp;most probably evolved from&amp;nbsp;&lt;/span&gt;&lt;i&gt;Toweius pertusus&lt;/i&gt;&lt;span&gt;&amp;nbsp;in the latest Palaeocene and gave rise to&amp;nbsp;&lt;/span&gt;&lt;i&gt;T. magnicrassus&lt;/i&gt;&lt;span&gt;&amp;nbsp;in the early Eocene.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1144/jm.12.1.91</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Copernicus Publicatons</dc:publisher>
  <dc:title>Reappraisal of three calcareous nannofossil species: Coccolithus crassus, Toweius magnicrassus, and Toweius callosus</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>