Theropods
Hatching of eggs was common among theropods. However, according to some information, not females were sitting on the nests, as is customary in the animal world, but males. Like modern emus, the male therapist leads one or more females into the nest, which lay eggs. Then all the care of the children falls on dad.
For a long time, it was believed that predatory dinosaurs were not the best parents. But this opinion was refuted by oviraptor, who defended his laying with his life. Previously, scientists thought that the eggs belong to the protoceratops, whose raptor eggs intended to steal. However, it later turned out that it was his own nest.
Zauropods
These guys can not boast of parental instincts. They prefer to take quantity, not quality. Laying eggs a little less than feces, they continue to calmly wander about their business.
The cubs hatch alone, helpless and weak. A large proportion died from the teeth of predators, and who survived - that fellow. Grown up individuals joined the herd, if such came across.
Incidentally, outside the herd, even with a large zauropod, the odds against several large predators were slim. What can we say about the cubs ...
It would seem an extremely unprofitable breeding strategy, but still this did not prevent them from existing for quite a long time.
These were Saurischia dinosaurs, let's move on to the Ornithischia dinosaurs.
Their classification is somewhat more complicated, so I will go over them in less detail.
Ornithischia are divided into ornitopods, ankylosaurs, stegosaurs, and cerapods.
The mass laying of eggs was widespread among cerapods and ornithopods. They found safe places and settled in whole nest colonies. The hatching cubs sat with their parents in these dinosaur villages for a long time.
Questions about the attitude to the offspring of stegosaurs and ankylosaurs are still the subject of controversy.
It is believed that they buried eggs in the warm sand, not hatching them, but cared for and protected from the young herd from predators.