Mastodonsaurus: Beast of the Week

 This week we'll be checking out a gigantic swamp beast.  Make way for Mastodonsaurus!

Mastodonsaurus was a member of the ancient order of vertebrates, called the temnospondyls, which were related to today's amphibians. (some studies suggest modern amphibians are also a branch of the temnospondyl order) Mastodonsaurus includes a few species, which lived in what is now Eurasia, fossils found in Germany, England, and Russia, during the Triassic period, 230 million years ago.  Mastodonsaurus was a meat-eater when alive and the largest species, Mastodonsaurus giganteus, could exceed 20 feet (6m) in length from snout to tail.  The genus name translates to "breast tooth lizard" which is a bit misleading since it wasn't a lizard nor do any of its teeth particularly resemble breasts of any kind. (But the broken one that was first examined by scientists who named it apparently did.)

Life reconstruction in watercolors of a territorial dispute between two Mastodonsaurus giganteus by Christopher DiPiazza.

Mastodonsaurus had a proportionally huge, flattened, skull, with large eye sockets on the top.  This is an adaptation to be able to raise its eyes above the water and still stay relatively hidden while stalking prey. Modern crocodilians and certain frogs have the same feature for the same purpose.  The inside of Mastodonsaurus' mouth was lined with sharp, cone-shaped teeth, ideal for making sure whatever animal it bit couldn't escape.  The most astonishing feature, however, was the pair of extra long, tusk-like teeth growing up from the tip of its bottom jaw.  These two teeth would fit through actual holes present in the top of the animal's mouth when closed.  The rest of Mastodonsaurus' body reinforced the idea that it was primarily an aquatic animal.  It's legs were proportionally small and weak, but it had a long, strong tail that it could have used to propel itself through the water of its swampy home.  

Mastodonsaurus skull on display at the Muschelkalk Museum. Photo credit: Ghedoghedo 

Mastodonsaurus would have been the top predator of its environment.  At its adult size it would have been able to devour a variety of other animals that it shared its habitat with.  It was likely an ambush predator, relying on stealth to snap up fish that swam to close to its mouth, or even grabbing land animals as they came to the water to drink.  It is unlikely Mastodonsaurus would have left the water much when alive.  Its anatomy just wasn't equipped to spend extended time on land.  There are also fossil beds of many Mastodonsaurus that all died practically on top of each other.  This implies they were trapped in a body of water that was drying up as they were forced closer and closer to the center until their deaths.  

References

Damiani, Ross J. (2001). "A systematic revision and phylogenetic analysis of Triassic mastodonsauroids (Temnospondyli: Stereospondyli)". Zoological Journal of the Linnean Society. 133 (4): 379–482.

Moser, Markus& Schoch, Rainer 2007 "Revision of the type material and nomenclature of Mastodonsaurus giganteus (Jaeger) (Temnospondyli) from the middle Triassic of Germany" Palaeontology 505:1245-1266:

Schoch, R.R. (1999). "Comparative osteology of Mastodonsaurus giganteus (Jaeger, 1828) from the Middle Triassic (Lettenkeuper: Longobardian) of Germany (Baden-Württemberg, Bayern, Thüringen)". Stuttgarter Beiträge zur Naturkunde Serie B. 278: 1–175.