Maiasaura is a genus of ornithischian dinosaurs of the hadrosaurid family (duck-billed dinosaurs) of the ornithopod suborder that lived in the territory of modern North America in the Upper Cretaceous period. It is assumed that maiasaurs, like all hadrosaurids, lived in herds and were herbivores. Hadrosaurs were scientifically described by renowned paleontologist Jack Horner based on fossils from the Two Medicine Formation in Montana, where all known fossils come from.
The structure of the body of the Mayasaurus, apparently, did not differ in any features, neither in the dorsal crest, nor in the shell. A distinctive feature was the so-called “duck” nose, which contained up to 2 thousand teeth. Mayasaurus weighed presumably 2 3 tons, and its body length reached approximately 7 meters.
Maiasaurs lived in nesting colonies, which is characteristic of many modern bird species. The researchers found several very well-preserved nests in a very narrow space at once.
Since some of them contained fossils of freshly hatched or very young animals with not yet fully formed bones of the hind limbs, and the bottoms of the nests were littered with fragments of egg shells, paleontologists suggest that maiasaurs were nesting animals and crushed the shell while in the nest. The young dinosaurs must have stayed in the nest until they were old enough to go foraging with their parents.
This theory is also supported by the remains of well-chewed and presumably regurgitated plant food found in the nests. In addition, the Maiasaur nest arrangement, which was circular in shape at a depth of about 1 meter and a width of 2 meters, is also considered as evidence for the theory of the maiasaur nesting nature. Most of the eggs were in an upright position.
Their length was about 20 centimeters, while one end of the egg, immersed in the bottom of the nest, was pointed. The wall of the nest was supposedly built of silt or sandy clay, and its inner surface was lined with soft vegetation.
The fact that young maiasaurs could be nesting animals suggests that the parents were extremely active in caring for the hatched offspring. So, they most likely had to protect the nest from enemies, warm the eggs first, and then the cubs, and constantly bring them food. Hence the name of the genus, which in Greek means “lizard-good mother”.
This pattern of parenting, comparable to that of modern animals, seems surprising to dinosaurs, but the chances of young animals surviving in a nesting colony were significantly higher than if they had to leave the nest immediately after hatching and take care of themselves.
In addition, it has been proven that hadrosaurids were able to make sounds and thus could warn relatives of danger. It is assumed that the females always returned to the same place to breed and raise offspring. Young maiasaurs grew very quickly and after 2 years they reached a length of about 3 meters. Then their growth slowed down, and they reached full maturity at about 8 years of age.