Wednesday, 21 September 2011

types of trilobites and adaptions

Benthonic (e.g Calymene) 
  • generally large trilobites
  • had a lot of pleura which means they have the ability to enroll for protection - lots of legs 1 pleura = 2 legs
  • epifaulnal - they crawl on the sea floor looking for food as active hunters or scavengers
  • had very good eyes 360* vision, the eyes would have been sensitive to movement to detect food and predators an advantage over other bottom dwellers in the same enviroment- could explain why they where so successfull.

Pelagic (e.g. Agnostus)
They where blind as no eyes                                  
  • had few pleura, and therefore few legs or gills.
  • found in sediments such as shales formed in low energy deep waters
  • had a pelagic planktonic lifestyle
  • possible lack of eyes means in deep water where theres no light
  • they where small and probably light weight

Nektonic (e.g. Deiphon)

  •  These where small trilobites - to stay a float
  • show streamlining
  • actively swimming, possibly as active hunters
  • eyes on stalks- ability to see 360* and beneth
  • inflated glabella may be filled with fat org as to help to float
  • has lots of pleura , with spines - has many legs for swimming and spines to increase surface area

Burrowing (e.g. Trinucleus)

  • These trilobites lack eyes      
  • shovel like head
  • benthonic and infaunal
  • no eyes due to depth
  • dug shallow burrows for protection or to feed 
  • extended genal spines - to spread its mass on soft substrate
  • pitted cephalic fringe

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