Sunday, March 4, 2018

Lesothosaurus: Beast of the Week

Lets look at an early dinosaur that gives us important insight on how dinosaurs evolved.  Check out Lesothosaurus diagnosticus!

Lesothosaurus was a small, probably omnivorous dinosaur that lived in what is now southern Africa during the early Jurassic Period, between 199 and 189 million years ago.  From snout to tail it measured a little over six feet long.  The genus name translates to "Lesetho Lizard" in reference to Lesotho, the country in Africa in which the first fossils of this dinosaur were found.

Lesothosaurus life reconstruction.  The hair-like feathers are entirely speculative.  However, preserved feathers have been found in other basal onrnithischian dinosaurs that fossilized under different conditions.

Lesothosaurus was originally considered a very early ornithopod dinosaur.  However, as time has passed and more fossils have been found, it has become more likely that this little dinosaur was something even more basal, predating not just ornithopods, but all ornithischian dinosaurs, including the armored thyreophorans (stegosaurs and ankylosaurs) and the horned marginocephalians (ceratopsians and pachycephalosaurs)

Lesothosaururs had interesting dentition that has led paleontologists to believe it was an omnivore in life.  In the front of the jaws it would have had a small beak, probably ideal for picking at leaves to eat.  The jaws, themselves, had mostly small, leaf-shaped teeth that were probably for cutting up plants, but it also had long, pointed teeth growing from the front of its top jaw.  These long teeth may have been an adaptation to help strip leaves off stems and branches, but they also could have been effective at processing animal-based food.  When paleontologists compared the teeth of Lesothosaurus to similarly-shaped teeth of other dinosaurs that were more primarily plant-eaters, Lesothosaurus showed notable less ware on its teeth.  Since processing plants is tougher on teeth than meat, this suggested that it was not eating as much plants as these other dinosaurs, and likely was a meat-eater, too.  Lesothosaurus probably wasn't going after large prey, since its teeth weren't blade-like for shearing off chunks of flesh from carcasses, like those of most primarily meat-eating dinosaurs, but it very well could have gone after small prey, like invertebrates, or any other creature that could be eaten in one or two bites.

Lower jaw of Lesothosaurus showing the teeth that were likely best ad processing plants.  Image from Sciscio's 2017 paper, referenced below.


Lesothosaurus had proportionally very long legs and a long tail that was slightly stiffened in life.  This means that it was a fast and agile runner when alive.  Its primary defense against predators of its time was probably to run away given its anatomy.

That is all for this week!  As always feel free to comment below or on the facebook page!

References

Barrett, P. M., Butler, R. J., Yates, A. M., Baron, M. G., & Choiniere, J. N. (2016). New specimens of the basal ornithischian dinosaur Lesothosaurus diagnosticus Galton, 1978 from the Early Jurassic of South Africa.

Butler, Richard J.; Upchurch, Paul; Norman, David B. (2008). "The phylogeny of the ornithischian dinosaurs". Journal of Systematic Palaeontology. 6 (1): 1–40.

Butler, R.J. (2005). "The 'fabrosaurid' ornithischian dinosaurs of the Upper Elliot Formation (Lower Jurassic) of South Africa and Lesotho". Zoological Journal of the Linnean Society. 145 (2): 175–218.

Matthew G. Baron; David B. Norman; Paul M. Barrett (2016). "Postcranial anatomy of Lesothosaurus diagnosticus (Dinosauria: Ornithischia) from the Lower Jurassic of southern Africa: implications for basal ornithischian taxonomy and systematics". Zoological Journal of the Linnean Society. in press.

Matthew G. Baron; David B. Norman; Paul M. Barrett (2016). "Postcranial anatomy of Lesothosaurus diagnosticus (Dinosauria: Ornithischia) from the Lower Jurassic of southern Africa: implications for basal ornithischian taxonomy and systematics". Zoological Journal of the Linnean Society. in press.

Sciscio L, Knoll F, Bordy EM, de Kock MO, Redelstorff R. (2017). Digital reconstruction of the mandible of an adult Lesothosaurus diagnosticus with insight into the tooth replacement process and diet. PeerJ, 5:

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