Maiasaura

**Name:** *Maiasaura* ‭(‬Caring/Good mother lizard‭)‬.
**Phonetic:** My-ah-sore-ah.
**Named By:** Jack Horner‭ & ‬Robert Makela‭ ‬-‭ ‬1979.
**Classification:** Chordata,‭ ‬Reptilia,‭ ‬Dinosauria,‭ ‬Ornithischia,‭ ‬Ornithopoda,‭ ‬Hadrosauridae,‭ ‬Saurolophinae,‭ ‬Brachylophosaurini.
**Species:** *M.‭ ‬peeblesorum‭* (‬type‭)‬.
**Diet:** Herbivore.
**Size:** Around‭ ‬9‭ ‬meters long.
**Known locations:** USA‭ ‬-‭ ‬Montana‭ ‬-‭ ‬Two Medicine Formation.
**Time period:** Late Campanian of the Cretaceous.
**Fossil representation:** Remains of over‭ ‬200‭ ‬individuals from newly hatched juveniles to adults including nests.

At up to nine meters long *Maiasaura* was not amongst the largest known hadrosaurid dinosaurs,‭ ‬though it still tipped the scale to be considered big for its kind.‭ ‬Like with its hadrosaurid relatives,‭ *‬Maiasaura* is thought to have been a primarily bipedal dinosaur,‭ ‬though one that was at least capable of balancing if not walking upon just its hind legs.‭ ‬The exact posture assumed was probably more dependent upon what the *Maiasaura* in question was actually doing at the time.‭ *‬Maiasaura* had a low crest on top of it snout and because it is solid,‭ ‬this indicates that *Maiasaura* was one of the saurolophine hadrosaurs.
*Maiasaura* might appear to be a rather plain looking hadrosaurid,‭ ‬but its real importance is not about its looks but upon the remains of nests that members of this genus created.‭ ‬One of the most significant fossil sites associated with *Maiasaura* is an area that we know today as‭ ‘‬Egg Mountain‭’‬.‭ ‬Here a concentration of nests spread apart at distances of around seven meters from each other,‭ ‬each containing around thirty to forty eggs about fifteen centimetres across were found with multiple remains of *Maiasaura* scattered around them.‭ ‬Some of these remains were of juveniles too large to have just hatched with underdeveloped rear legs.‭ ‬The skulls of juveniles also have very different proportions to those of the adults,‭ ‬though this is quite common in vertebrates.‭ ‬In addition to these were remains of adult *Maiasaura*,‭ ‬something that suggests that adults would not just lay their eggs and wander off,‭ ‬but stay close to the nests and their young for some time.‭ ‬Bearing in mind the underdeveloped rear eggs of the younger juveniles it’s possible that a more precise scenario is that the adult *Maiasaura* would move away from the nests for short periods while they foraged to bring food back to the nest while‭ ‬the hatchlings became strong enough to walk around and forage for themselves.

The sheer number of nests and *Maiasaura* fossils from the Egg Mountain site is proof that *Maiasaura* would congregate in large numbers during the nesting‭ ‬period,‭ ‬however it remains impossible to say‭ ‬for‭ ‬certain how this genus lived when not nesting.‭ ‬It’s not impossible that when *Maiasaura* were not nesting they moved around in much smaller groups to reduce the impact on the ecosystem in a given area,‭ ‬more mouths in one place would after all cause more destruction to the plants growing there,‭ ‬increasing the amount of time necessary for the ecosystem to recover,‭ ‬although hadrosaurids like *Maiasaura* might have been continually on the move and only staying put for short periods such as nesting.

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