Habrosaurus: Beast of the Week

 This week we'll be checking out a prehistoric amphibian.  Make way for Habrosaurus!

Habrosaurus was a salamander that lived in what is now Alberta, Wyoming and Montana, during the late Cretaceous period into the early Paleocene (surviving the asteroid that wiped out most of the dinosaurs), from 68 to 58 million years ago.  From snout to tail Habrosaurus is estimated to have been over five feet (1.6 meters) long, making it one of the largest salamanders of all time.  When alive Habrosaurus likely would have likely preyed on smaller aquatic animals, like shrimp and mollusks. (all amphibians are predators at least as adults) The genus name translates to "Graceful Reptile" even though it was and amphibian, not a reptile.

Life reconstructions in watercolors of Habrosaurus dilatus by Christopher DiPiazza.

There are currently two species of Habrosaurus known on the fossil record.  Habrosaurus prodilatus is the older species, lived in what is now Alberta, Canada, and would have shared its habitat with dinosaurs like Styracosaurus, Parasaurolophus, and Gorgosaurus.  Habrosaurus dilatus is the later species and lived in what is now Western United States, and would have shared its home with dinosaurs, like Triceratops, Ankylosaurus, Pachycephalosaurus, and Tyrannosaurus.

Habrosaurus was a member of the siren (sirenidae) family of salamanders which have numerous species still alive today, all native to the southern United States.  Sirens are characterized by having extremely long, eel-like bodies, front limbs only (no back legs), gills, and live their entire lives in freshwater but can also burrow into the mud if they need to.  Unlike many amphibians, sirens do not undergo metamorphosis, but rather stay fully aquatic their entire lives, simply growing larger as they age.  

Teeth and jaw fragments from Habrosaurus dilatus from Gardner's 2003

 paper linked below.

Fossils of Habrosaurus dilatus' teeth indicate that it specialized in eating hard-shelled prey, like snails and shrimp.  Both species also may have been preying on fish and other animals small enough to fit in their mouths if they wandered too close.  Living sirens are some of the few kinds of amphibians known to actually be omnivores as adults, supplementing their mostly meat diet with water plants, as well.  There is no way to know if Habrosaurus may have eaten some plants as well when it was alive.  iLike living sirens, Habrosaurus likely spent its time on the muddy bottom of swamps and other bodies of fresh water, where it relied on secrecy to ambush prey.  I wonder how many unsuspecting large dinosaurs were bitten on the nose by an angry Habrosaurus, as they tried to take a drink?

That's all for this week!  Leave a comment below!

References

Gardner, James D. (November 2003). "Revision of Habrosaurus Gilmore (Caudata; Sirenidae) and relationships among sirenid salamanders". Palaeontology. 46 (6): 1089–1122.

Hill, R. L., Mendelson, J. R. & Stabile, J. L. 2015. Direct observation and review of herbivory in Sirenidae (Amphibia: Caudata). Southeastern Naturalist 14, N5-N9.

K. Roelants, D.J. Gower, M. Wilkinson, S.P. Loader, S.D. Biju, K. Guillaume, L. Moriau, F. Bossuyt (2007) Global pattern of diversification in the history of modern amphibians. Proc. Natl. Acad. Sci. USA, 104: 887-892