A groundbreaking study from Ohio State University has provided the earliest direct evidence that adult Maiasaura peeblesorums fed their young better food, a behavior previously thought to be exclusive to birds and mammals.

The nesting sites left behind by Maiasaura peeblesorum in Montana, dating back 75 to 80 million years, earned this duck-billed dinosaur the moniker “good mother lizard.”

Living up to its reputation, a new study of fossilized teeth has demonstrated that these dinosaurs showed extensive care for their young by ensuring they received nutritious food.

This pattern, observed in modern birds, rarely appears in reptiles and other dinosaurs; this discovery revolutionizes our understanding of dinosaur parental care and suggests more complex social systems.

Dinosaurs who cared for their young

Researchers from Ohio State analyzed the microscopic wear on the teeth of Maiasaura peeblesorum at various ages. The dental microwear tests they conducted investigated the micro-abrasions and polish on the teeth.

“The dental batteries of hadrosaurs appear to be functionally analogous to the cheek teeth of large mammalian herbivores,” the study authors explained. “However, the method of chewing was radically different.”

“In mammals, shearing wear is found on the slopes of the cusps, at an orientation approximately perpendicular to the occlusal plane, and is accompanied by directional wear ‘striations.’ Crushing wear is found on the tips of the cusps, which meet with basins in the opposing teeth, and there is no obvious directional component to the ‘pits’ that this wear produces.”

Juveniles exhibited patterns of crushing wear on their teeth, while adults showed signs of shearing wear, suggesting they consumed different types of food. The study states, “Adults were bringing food back to the nest for their young that was of lower fiber content and hence higher caloric content than what they themselves consumed.”

The young Maiasaura ate softer, higher-protein food, while the mothers consumed tougher, less nutritious, high-fiber plant material, as noted by Bioengineer. Researchers also propose that the adults may have fed their young partially regurgitated food, a behavior seen in birds. Alternatively, the young might have fended for themselves, similar to lizards.

A new behavior for the dinosaurs

As highly social animals, these herbivores lived in herds, which influenced their reproductive strategies—a rarity for the Mesozoic era. Today, per Phys, mammals display this behavior. In certain mammals like horses, antelopes, and cows, researchers observed dental patterns similar to those found in adult Maiasaura. By comparing the teeth, they found that these dietary shifts allowed the young to grow quickly, giving them an advantage in the wild.

“The urge for a bird to feed its young is a very old behavior,” stated the lead author in Phys. “What we’re providing is evidence that this behavior probably predates the origin of birds and may even trace back to the origin of dinosaurs.”

This practice, deeply integrated into a lineage, established a new understanding of a continuity of care that birds would carry on their wings once they took flight, according to Bioengineer. As a species, the Maiasaura continued to stand out as exceptional among dinosaurs.