| Asaphus
          latusTrilobites 
        Order Asaphida, Family Asaphidae Geological 
        Time: Middle Ordovician, Asery Horizon Size: 88
        mm Fossil Site: 
        Wolchow River Region, St Petersburg, Russia 
  
 
          |  Description:
                  A is a less common trilobite Asaphid, Asaphus
                  latus, a name derived from its  broader thorax. The
                  region in which these trilobites lived was subject to dramatic
                  changes in salinity and turbidity,
                  and the trilobites were able to make rapid (geologically speaking)
                  evolutionary adjustments. These adjustments were thought to
                  be able
              to allow them to see both predator and prey more easily.  Coming
              from an inland sea during the lower to middle Ordovician, the Russian
              trilobites from near Saint Petersburg, Russia participated in the Great
              Ordovician Radiation, which saw marine animal diversity increase
              three-fold more than the Cambrian Explosion. The Russian
              asaphid trilobites are a particularly interesting example of
              descent with modification.
 Also
                see: Russian Trilobites Asaphid
                Trilobites Russian
              Ordovician Asaphus Trilobites Evolutionary Sequence |  |