Pikaia

Pik-ay-ah.
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John Stewart

Paleoecologist

John Stewart is a distinguished paleoecologist whose work has significantly advanced our understanding of prehistoric ecosystems. With over two decades dedicated to unearthing fossils across Asia and Africa

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Name

Pikaia ‭(‬after Pika Peak‭)‬.

Phonetic

Pik-ay-ah.

Named By

Charles Walcott‭ ‬-‭ ‬1911.‭

Classification

Chordata,‭ ‬Cephalochordata‭?

Diet

Uncertain.

Species

P.‭ ‬gracilens‭

Size

Around‭ ‬38‭ ‬millimetres long.

Known locations

Canada,‭ ‬British Columbia‭ ‬-‭ ‬Burgess Shale.

Time Period

Middle Cambrian.

Fossil representation

Many individuals.

In Depth

       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.

SPECIES SPOTLIGHT