Final answer:
The poorly formed limb joints of hatchling Maiasaura suggest that they were altricial, meaning they were not fully developed and required parental care after hatching.
Step-by-step explanation:
The poorly formed limb joints of hatchling Maiasaura suggest they were altricial. Altricial animals are those that are not fully developed at birth and thus require care and feeding by the parents. In contrast, precocial animals are relatively mature and mobile from the moment of birth or hatching. The determination that the limb joints of hatchling Maiasaura were underdeveloped supports the idea that these dinosaurs were unable to move effectively on their own and likely needed parental care, much like modern-day altricial birds.
Given that modern birds are endothermic and are considered to have evolved from dinosaur ancestors, it would be plausible to theorize that the Maiasaura also showed similar endothermic traits. However, their level of development at hatching is what categorizes them as altricial.