Marrella
Name: Marrella.
Phonetic: Mar-rel-lah.
Named By: Charles Doolittle Walcott - 1912.
Classification: Arthropoda, Marrellomorpha,
Marrellida, Marrellidae.
Species: M. splendens
(type).
Diet: Detritivore.
Size: About 2 centimetres long.
Known locations: Canada, British Columbia -
Burgess Shale.
Time period: Mid Cambrian.
Fossil representation: Over 25,000 individuals
have been recorded.
The
genus Marrella has the distinction of being the
most common animal
found in the world famous Burgess Shale. When first described in
1912 Marrella was thought to possibly be a lace
crab, and then
later a trilobite. Later studies have now concluded however that
Marrella is actually a stem arthropod, related to
the ancestors of
true arthropods, yet not necessarily an ancestor itself.
Marrella
tended to have around twenty-four to twenty-six body segments, and
two large pairs of rearward facing spines. The legs of Marrella
are
interesting in that the upper legs had gills for absorbing oxygen from
the water. Some better preserved specimens reveal the presence of a
diffraction grating pattern, meaning that in life Marrella
would have
had an iridescent sheen. All in all Marrella is
thought to have
been a bottom dweller that sifted through the soft sediment for morsels
of organic matter to eat.
Further reading
- Redescription of Marrella splendens
(Trilobitoidea) from the
Burgess Shale, Middle Cambrian, British Columbia. - Bulletin –
Geological Survey of Canada 209 - H. B. Whittington -
1971.
- Colour in Burgess Shale animals and the effect of light on
evolution in the Cambrian. - Proceedings of the Royal Society B:
Biological Sciences 265 (1400): 967–972. - A. R.
Parker - 1998.
- Moulting arthropod caught in the act. - Nature 429
(6987): 40. - D. C. Garc�a-Bellido & D. H.
Collins - 2004.
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