Sunday, September 14, 2014

Dreadnoughtus: Prehistoric Animal of the Week

This week we will be looking at a recently discovered behemoth of a dinosaur.  Make way for Dreadnoughtus schrani!  Dreadnoughtus was a huge plant-eating dinosaur that lived in what is now Argentina, during the Late Cretaceous, roughly 77 million years ago.  It was one of the largest land animals of all time, measuring eighty five feet long from snout to tail.  It is considered a titanosaur, which was a kind of sauropod (long-necked dinosaurs) that survived all the way to to the end of the Mesozoic Era.  The genus name, Dreadnoughtus, translates to "fears nothing".  This is in reference to this animal's immense size and that it probably had no predators to fear once it reached adulthood.  Dreadnought is also the name of a kind of giant, armored battleship which were first launched during the early 1900s.  Two of these massive ships were also in the Argentine navy making this dinosaur's name that much more appropriate. (and badass) 

life reconstruction painting of Dreadnoughtus schrani by Christopher DiPiazza.

Dreadnoughtus is an exciting discovery for a few reasons.  One reason is between the two individual animals found, a lot of bones were unearthed, more than what is typical for large dinosaurs.  In fact, going by types of bones (Once you have the left humerus, for instance, you can safely assume the right one is the same, just mirrored even if it was never found.), over 70% of Dreadnoughtus' anatomy is known.  This is extremely rare for a large dinosaur since in order for fossilization to take place, the animal's remains need to be buried rapidly after death.  This is more common with small animals. Its more likely for mud or sand to completely cover a dead pigeon-sized Anchiornis' entire body, for instance, within a matter of minutes.  But what are the chances eighty five feet of dead dinosaur would have been rapidly buried?  Normally when large animals, especially sauropods, die, the remains would have sat there for a while, scavengers would pick at them, maybe even scatter them around to different places.  Millions of years later, paleontologists are lucky to find one vertebra that fossilized to study.  (Doesn't stop scientists from naming new species though!)  Because of this Dreadnoughtus is considered the largest, well understood, dinosaur known to science.  What I mean is that there are other dinosaurs that have been discovered that may have been bigger than Dreadnoughtus, but they are only known from highly fragmentary remains and scientists tried to hypothesize their full sizes by scaling imaginary skeletons around the few bones that were actually found.

Image from the 2014 paper by Kenneth Lacovara, referenced below.  Note the size compared to an average human diagram and how many bones (shown in white on the diagram) were actually discovered!

Dreadnoughtus' bones gave scientists a lot of answers as to how large titanosaurs would have looked and possibly walked.  Its front limbs were shorter than its hind legs, so it is likely that its neck was held more parallel with the ground nomrally.  It could have raised its neck for short periods of time for eating the tops of trees or displaying for members of its own species possibly, however.  Dreadnoughtus' neck was extremely long and was about half the animal's total length.  The tail, however, was relatively short, only thirty feet long.  (only a thirty-foot tail...I feel weird saying that.)  Most Titanosaurs, like Dreadnoughtus' smaller cousin, Saltasaurus for instance, had a pretty wide stance with reference to to their legs and bodies.  Dreadnoughtus, however, although having a still pretty wide stance, held its legs more underneath its body in comparison to its kin.  We know this because of the angles at which the leg and arm bones attach into their sockets.  These extremely powerful limbs would have acted like pillars, supporting Dreadnoughtus' immense bulk as it walked, and stood and...did pretty much everything I guess.  Other titanosaurs, like Saltasaurus, are known to have had bony armor embedded in their skin.  There is not evidence that suggests this in Dreadnoughtus so it is a mystery as to whether or not it had such a defense adaptation.  It wouldn't surprise me, however, if an animal as large as Dreadnoughtus, lacked armor as its size alone (as an adult, at least) would have made it impossible to kill for any known predator.

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

References

Lacovara, Kenneth J.; Ibiricu, L.M.; Lamanna, M.C.; Poole, J.C.; Schroeter, E.R.; Ullmann, P.V.; Voegele, K.K.; Boles, Z.M.; Egerton, V.M.; Harris, J.D.; Martínez, R.D.; Novas, F.E. (September 4, 2014). "A Gigantic, Exceptionally Complete Titanosaurian Sauropod Dinosaur from Southern Patagonia, Argentina". Scientific Reports. doi:10.1038/srep06196. Benson, Roger B. J.; Campione, Nicolás E.; Carrano, Matthew T.; Mannion, Phillip D.; Sullivan, Corwin; Upchurch, Paul; Evans, David C. (May 6, 2014). "Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage". PLOS Biology. doi:10.1371/journal.pbio.1001853.

Wilson, Jeffrey A.; Carrano, Matthew T. (June 1999). "Titanosaurs and the origin of "wide-gauge" trackways: a biomechanical and systematic perspective on sauropod locomotion". Paleobiology 25 (2): 252–267. Retrieved 31 August 2014.

Wilson, J. A. (February 2006). "An Overview of Titanosaur Evolution and Phylogeny". III Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno: 169–190.

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