Maiasaura: Prehistoric Animal of the Week

Happy Mother's Day!  Today mothers of all kinds get recognized for all the wonderful things they do for their children.  (Honestly every day should be like mothers day but lets not say no to an official holiday either)  Did you know that we have scientific evidence of a number of dinosaurs that were probably devoted mothers as well?  It's true.  Good parenting is evident in most birds and crocodilians and even in a few species of snakes, lizards and tortoises!  It should be no surprise that certain non-avian dinosaurs shared these caring characteristics with their modern relatives.  Today we honor Maiasaura peeblesorum, the "Caring Mother Dinosaur".

Maiasaura peeblesorum mother and baby life reconstruction by Christopher DiPiazza.

Maiasaura belongs to the hadrosaurid family, also commonly referred to as the "duck-billed dinosaurs".  These dinosaurs get their casual name because they had wide, flat bills sort of like modern ducks (they are not directly related to modern ducks, however) which they may have used for eating tough plant material.  Unlike ducks, hadrosaurs had hundreds of tiny teeth in their mouths for chewing.   Maiasaura lived in what is now Montana, USA, 74 million years ago during the late Cretaceous Period.  Unlike a lot of other dinosaur species where we are lucky to find even a partial skeleton of, Maiasaura is known from literally hundreds of complete or nearly complete fossilized specimens, ranging from babies just out of the egg all the way up to thirty foot long adults!

Skeletal mount of Maiasaura adult and juvenile.

I chose Maiasaura to review on Mother's Day because it was the first non-avian dinosaur discovered that provided concrete evidence of parental care in an extinct dinosaur.  Back in the 1980s hundreds of fossilized Maiasaura nests with eggs along with the of bones from adults and juveniles were unearthed in an area of Montana called the Two Medicine Formation.  The reason why we know these dinosaurs were actually caring for their young and not simply dumping the eggs off like some other reptiles do is that some of the skeletons from babies were too big to be newborns, yet still were in the nest.  Why would a baby dinosaur stick around after hatching?  Because its parents were still feeding and protecting it, that's why.  This is very similar to how most modern birds care for their young.  The actual hatchling Maiasaura that were discovered appear to have hatched with legs still too underdeveloped to walk around.  This is an example of an altricial animal which means that it requires care from its parents in order to survive upon being born.  This is also observable in many kinds of modern birds.

Maiasaura hatchling reconstruction by Jack Horner.  The eggs were about the same size as Ostrich eggs.

The nests of these Maiasaura each had a radius of about twenty feet of space around them, forming an almost geometric network pattern on the ground of hundreds of nests.  This is also something that can be observed in nesting colonies of some modern species of bird.  Unlike birds, however, Maiasaura wouldn't have been able to sit on its eggs to incubate them.  Instead it would have gathered vegetation to use as a blanket.  As the vegetation rots, it gives off heat to keep the eggs warm.  This kind of nesting behavior is seen in modern crocodilians.

Nesting colony of modern Gannets.  Note how they are all evenly spaced from each other and that the baby (in the center nest) hasn't left.  Like Maiasaura, it is incapable of survival for a period of time after hatching without its parents.

Thanks to this discovery, we know that at least certain kinds of dinosaurs did care for their young.  Since then parenting behavior has also been discovered in a few other kinds of dinosaur including a few theropods.  It is likely many other kinds of dinosaur were also good parents though. 

That's all for this week!  As always feel free to comment below or on our facebook page if you would like to see any particular dinosaur or other prehistoric creature reviewed.  Happy Mother's Day!  

References

 Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. The Age of Dinosaurs. Publications International, LTD. p. 116-117. ISBN 0-7853-0443-6.

 Horner, Jack and Gorman, James. (1988). Digging Dinosaurs: The Search that Unraveled the Mystery of Baby Dinosaurs, Workman Publishing Co.