Pikaia

Name: Pikaia ‭(‬after Pika Peak‭)‬.
Phonetic: Pik-ay-ah.
Named By: Charles Walcott‭ ‬-‭ ‬1911.‭
Classification: Chordata,‭ ‬Cephalochordata‭?
Species: P.‭ ‬gracilens‭ (‬type‭)‬.
Diet: Uncertain.
Size: Around‭ ‬38‭ ‬millimetres long.
Known locations: Canada,‭ ‬British Columbia‭ ‬-‭ ‬Burgess Shale.
Time period: Middle Cambrian.
Fossil representation: Many individuals.

       Pikaia has been one of the most talked about creatures discovered from the Cambrian era Burgess Shale,‭ ‬yet there is still controversy over exactly what it was.‭ ‬In‭ ‬1979‭ ‬Simon Conway Morris noted the presence of a proto-notochord,‭ ‬an anatomical structure that later creatures would develop into a spine creating the first true chordates.‭ ‬Chordates are better known as vertebrates,‭ ‬animals that have a hard backbone that also includes human beings.‭ ‬Morris however went so far as to suggest that Pikaia was itself a chordate,‭ ‬which in turn has led to popular speculation that Pikaia may have been‭ ‘‬the‭’ ‬ancestor to all vertebrates,‭ ‬including humans.
       This is the main source of the controversy surrounding Pikaia,‭ ‬because not everyone is convinced that Pikaia are even chordates at all.‭ ‬It has‭ ‬been suggested to have had‭ ‬a segmented exoskeleton as well as the‭ ‬presence of short tentacles,‭ ‬both anatomical features of invertebrates,‭ ‬creatures without a backbone.‭ ‬In fact,‭ ‬when Pikaia was first described by Charles Walcott in‭ ‬1911,‭ ‬it was as a kind of polychaete worm.‭ ‬Today Pikaia is more commonly envisioned as a cephalochordate,‭ ‬similar to the lancelets that we know today.‭ ‬With this in mind Pikaia might have been related to the true ancestors of the chordates,‭ ‬yet was still separate from them.
       The exact lifestyle of Pikaia is still uncertain,‭ ‬due to its similarity to lancelets it was probably a free swimming creature that moved through the water with side to side undulations of its body.‭ ‬As it swam through the water it may have picked up small morsels of organic matter that were then digested in the gut.‭ ‬Although merged with the body,‭ ‬Pikaia is noted for still having a distinct head.

Further reading
-‭ ‬The Middle Cambrian fossil Pikaia and the evolution of chordate swimming -‭ ‬T.‭ ‬Lacalli‭ ‬-‭ ‬2012.
-‭ ‬Organic preservation of non-mineralizing organisms and the taphonomy of the Burgess Shale -‭ ‬N.‭ ‬J.‭ ‬Butterfield‭ ‬-‭ ‬1990.
- Pikaia gracilens Walcott: stem chordate, or already specialized in the Cambrian? - J. Mallatt, J & N. D. Holland - 2013.



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