Reconstruction by Marianne Collins
When: Cambrian (~520 - 500 million years ago)
Where: First described from Burgess Shale formation in BC, Canada, now found fairly worldwide in beds of simular ages.
What: Tuzoia is a bivalve arthropod first known from the Burgess Shale formation. It may seem odd that an animal that looks like an upside down taco with sunglasses on is an arthropod, but this is not as crazy as it first appears! In the crustacean subgroup of Arthropoda many taxa have a bivalve (2 parts that cover a great deal of the animal with a hinge in the middle) shell, if not as adults then in their larva forms. One example of a living group that has this type of shell as adults is the ostracods, and more well known taxa such as lobsters have shells such as this in their juvenile stages. To complicate matters even more, there are a number of fossil taxa, some also known from this locality, that have simular shells.
The placement of Tuzoia -within- arthropoda is more problematic. It is possible that it on the lineage leading to crustaceans, or at least somewhere in that general vicinity, but it is conservatively held as a ‘stem arthropod’ in most classifications for now. As most of the animal is hidden within its shell, most of the features that would confidently inform its position are unknown. I didn’t include any of the images, as they are really hard to interpret, but there are specimens known with stalked eyes and possible antennae peeking out from its spiky ornamented shell. As removing the shell would potentially destroy any preserved soft-parts beneath it, this has not been done on any specimens, to my knowledge. In my opinion they should toss this sucker into a CT scanner to find out what is underneath there.
In life Tuzoia swam freely though the water column. Without knowledge of its mouth parts its difficult to know if it was a filter feeder or a small predator. Tuzoia reached a maximum size of about 7 inches (~180 mm).
For more information and images see: http://www.burgess-shale.rom.on.ca/en/fossil-gallery/view-species.php?id=125&m=5&&ref=i
And check out the Burgess Shale tag on Daily Fossil to see other odd odd animals from this formation!