Saturday, June 15, 2013

Eocursor: Prehistoric Animal of the Week

This week we are going back farther than usual to the Triassic when dinosaurs first started to get a foothold as the dominant land vertebrates on earth.  Lets check out Eocursor parvusEocursor translates to "Dawn Runner" because it was a very early dinosaur and its extremely long legs show us that it was probably a fast runner.  This dinosaur lived about 210 million years ago in what is now South Africa and would have eaten plants when it was alive.  It was first discovered in the 1990s but wasn't formally described until 2007.

Life reconstruction of Eocursor parvus by Christopher DiPiazza

Eocursor was not large, measuring only about three feet long from head to tail.  It had no special armor, horns, spikes, large teeth or anything else that some other extinct dinosaurs had that would make it formidable but it is nonetheless an extremely important discovery.  You see, almost every other dinosaur we know of from the Triassic is either some sort of theropod, like Coelophysis or a prosauropod, like Plateosaurus.  Very rarely does anyone find a dinosaur like Eocursor which is in the same group as and likely the ancestor of the plant-eating, beaked dinosaurs like ceratopsians, thyreophorans and ornithopods.  We call this group the ornithiscian dinosaurs or "bird hipped dinosaurs" (ironic because its the other sauriscian "lizard hipped" theropods that were actually directly related to birds).  It may not look like much now, but Eocursor's lineage would evolve into some of the most successful and widespread dinosaurs of the Mesozoic!

Eocursor parvus bones

Like I said before, Eocursor had extremely long legs which would have come in handy(or footy HA!) when avoiding all those hungry meat-eating theropods and crocodilomorphs of its time.  We can tell this because its tibea(lower leg bone right below the knee) was much longer than its femur (thigh bone) which is a characteristic of swift-runners.  It also had pretty long and strong arms that would have had five grasping fingers.  This might have aided it when foraging for plants to eat.  Its head was small and possessed small teeth that look like they would have been suitable for cutting leaves and other such plant material.  Even thought the top of its skull was never discovered, I would be willing to bet Eocursor also had large eyes, which is a trait common in other small, fast-moving, plant-eating dinosaurs.

References

 Butler, Richard J.; Roger M. H. Smith and David B. Norman (2007). "A primitive ornithischian dinosaur from the Late Triassic of South Africa, and the early evolution and diversification of Ornithischia". Proceedings of the Royal Society B: Biological Sciences 274 (1621): 2041. doi:10.1098/rspb.2007.0367

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