Your Daily Fossil

Wiwaxia

When: Mid-Cambrian (515-500 million years ago)

Where: British Columbia, Canada, Northern Australia, and China

What: Wiwaxia is another odd form from the Burgess Shale fossil deposit in BC, Canada. This animal was small, only about 2 inches (~5 cm) long at the most, with many specimens much smaller than this. The smallest individuals represent juveniles, at only .13 inches (~.34 cm) long.  It was covered in small armored plates, with larger projections extending dorsally. It is thought the small plates protected it from smaller predators, and the large spikes made it hard for larger predators to crack this armor. The smallest individuals lack these spines, implying they grew in as the animal matured. Its ventral surface was soft and unarmored, with a set of hard ‘teeth’ at the anterior end, showing Wiwaxia fed by moving over the sediment and filtering out microscopic food particles.

As with many of the Burgess Shale fauna the phylogenetic placement of Wiwaxia is greatly debated. The story is the same as for taxa such as Hallucigenia and Opabinia; it is unknown if this form is a representative of a phylum that has no living members today, or if it is an early branch off a phylum that has persisted to the modern day. The proposed living relatives of Wiwaxia are polychaete worms and mollucs, but there is not espically strong support for either placement. 

For more images of Wiwaxia check out its page on the amazing Burgress Shale Website, presented by the Royal Ontario Museum. 

Also Wiwaxia is really fun to say out loud, you should try it!