Sunday, May 7, 2017

Zalmoxes: Beast of the Week

This week we will be checking out an unusual ornithopod.  Check out Zalmoxes!

Zalmoxes was a plant-eating dinosaur that lived in what is now Romania, during the Late Cretaceous, between 70 and 66 million years ago.  There are currently two named species, Zalmoxes robustus and Zalmoxes shqiperorumZ. shqiporum is deemed the "larger" species at about eight feet long from beak to tail, but Z. robustus's largest known individuals, at about six feet long, were determined to be sub-adults, so it is likely Z. robustus could have grown more than what the fossil record shows.  The genus name is in reference to Zalmoxis, a character from ancient Dacian (province in Romania) folklore.

Zalmoxes robustus life reconstruction in watercolors by Christopher DiPiazza.

Zalmoxes is considered an ornithopod dinosaur, and is currently thought to be within the iguanodontid clade on the dinosaur family tree.  This would make it a close relative of the more famous, Iguanodon, as well as Mantellisaurus, and Tenontosaurus.  However, within iguanodontidae, Zalmoxes is part of the more specific family, called rhabdontidae.  Rhabdontids were generally smaller, but robust, bipedal dinosaurs.  Despite that they are currently considered most related to iguanodontids, they have also been compared to the even smaller, and more lightly-built hypsilophodontids.

Possibly the most striking feature about Zalmoxes is its skull, which is large when compared to its overall body size.  At the tip of Zalmoxe's triangular-shaped skull, it had a short beak, that would have helped it clip vegetation.  This food would later be processed by its small teeth in the back, which were backed up by a very deep lower jaw.  This deep jaw, paired with the high ridge on the back of the skull, suggests there were large muscles attached in life, and therefore Zalmoxes would have had a very powerful bite.  Perhaps it specialized in eating a certain variety of tough plant?

Zalmoxes shqiporum skeletal mount on display in Brussels. By MWAK - Own work, Public Domain,  Note the high section on the top of the rear of the skull where muscles would have connected to the lower jaw. 

The part of the world that Zalmoxes was found in was an island during the late Cretaceous.  Some scientists have suggested Zalmoxes' smaller size, when compared to other ornithopods of its time is a result of island dwarfism.  Island dwarfism is one of several phenomenons that have been observed when animals from the mainland end up genetically isolated from the rest of their original population on an island.  Over time, this new, smaller population, can evolve smaller bodies to better adapt to their new environment.  Note that Zalmoxes lived at the very end of the Cretaceous, right be fore the mass extinction that wiped all of the dinosaurs (except birds) while the majority of other known iguanodontids flourished during the early Cretaceous.  By Zalmoxes' time, the duck-billed hadrosaurs had taken the niches iguanodontids once held.  Zalmoxes being separated from the rest of the world on an island may have been its saving grace in that it didn't have to compete with the same newer forms of dinosaurs its ancestors on the mainland did, and thus was able to persist up until the end of the Mesozoic.

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


Ősi, A.; Prondvai, E.; Butler, R.; Weishampel, D. B. (2012). Evans, Alistair Robert, ed. "Phylogeny, Histology and Inferred Body Size Evolution in a New Rhabdodontid Dinosaur from the Late Cretaceous of Hungary". PLoS ONE. 7 (9): e44318.

Weishampel, D.B.; Jianu, C.-M.; Csiki, Z.; Norman, D.B. "Osteology and phylogeny of Zalmoxes (n. g.), an unusual euornithopod dinosaur from the Latest Cretaceous of Romania" (PDF). Journal of Systematic Palaeontology. 1 (2): 65_123.

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