Sunday, March 2, 2014

Opabinia: Prehistoric Animal of the Week

This week marks the very first invertebrate Prehistoric Animal of the Week after two years.  This is totally inconsistent with the biodiversity of the world considering the fact that 98% of all animals actually don't possess backbones.  I guess we are just biased towards dinosaurs.  Even so, I must admit that this week's critter is a cool one.  Enter Opabinia regalis!

Opabinia lived all the way back 500 million years ago during the Cambrian age in what is now Canada.  Most of the world, including Opabinia's habitat, was in the ocean at the time.  According to the fossil record, it is during this time that the first multi-celled animals flourished...a lot.  In fact there was such a boom in biodiversity from what paleontologists can tell during this era, it has been nicknamed the "Cambrian Explosion".  Opabinia was one of the products of this...explosion.

Opabinia regalis reconstruction by Christopher DiPiazza.  Seriously, why has there not been a pokemon based on this yet?
 
This critter was small, only about 2.5 inches long, and would have swam around using paddle-shaped lobes lining the sides of its flattened body.  It also had six lobes surrounding its tail which may have helped it steer.  On its head it possessed five, large, spherical eyes and its mouth was underneath...and faced backwards. (evolution was in one of its weird experimental phases I guess)  Finally, in the front of this animal's body, there was a long tube that ended in a little grabber which was probably used to forage and bring food to the mouth.  H.P. Lovecraft would be all over this thing.


So we know what it looks like, we know where it lived, when it lived, and we know what it's called.  Still...what was it?  Well scientists were wondering that too.  There is some debate as to where exactly Opabinia falls on the family tree but most scientists can agree that it is at least closely related to arthropods. (jointed legs, exoskeleton...horseshoe crabs and scorpions for example)  Opabinia doesn't actually show any real evidence of having an exoskeleton or real jointed legs itself, though.  It does, however, have a segmented body, which led other scientists to think that it may be more closely related to annelids. (segmented worms like earthworms and leeches)  Finally, another group of scientists believe Opabinia is most closely related to a group of animals called tardigrades.  The most famous kind of tardigrade is called the Water Bear. (They are actually pretty bad-ass. Look them up after you read this)  Soooooo where does that leave Opabinia?  Latest research puts it at the base of the arthropod branch. 

Beautifully preserved Opabinia fossil from British Columbia, Canada.

Hope you enjoyed this week's Prehistoric Animal of the Week!  Not only was it the first invertebrate, but it is also the oldest animal, and probably the weirdest one we have reviewed to date.  It was also a request!  If you have a request of an animal you would like to see me review and paint leave a comment below or on our facebook page!

References

Budd, G. E. (1996). "The morphology of Opabinia regalis and the reconstruction of the arthropod stem-group". Lethaia 29 (1): 1–14. doi:10.1111/j.1502-3931.1996.tb01831.x.

Whittington, H. B. (June 1975). "The enigmatic animal Opabinia regalis, Middle Cambrian Burgess Shale, British Columbia". Philosophical Transactions of the Royal Society B 271 (910): 1–43 271. Bibcode:1975RSPTB.271....1W. doi:10.1098/rstb.1975.0033. JSTOR 2417412. Free abstract at Whittington, H. B. (1975). "The Enigmatic Animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia". Philosophical Transactions of the Royal Society B 271 (910): 1. Bibcode:1975RSPTB.271....1W. doi:10.1098/rstb.1975.0033.

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