Episode 176 – Hadrosaurs

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They’re sometimes called “duckbills” or the “cows of the Cretaceous,” and they were among the most successful and social of dinosaurs. This episode, we discuss the evolution, diversity, and unique features of Hadrosaurs.

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The “Duckbill” Dinosaurs

Hadrosaurs are famous for being among the most abundant and diverse dinosaurs of the Late Cretaceous. They belong to a broader group called ornithopods, which were quite diverse even outside of hadrosaurs themselves. Living all over the world throughout the Cretaceous Period and even earlier, ornithopods, and especially hadrosaurs, were some of the most successful herbivores of all time.

Early ornithopods were relatively small, bipedal herbivores with narrow mouths. Over time, new lineages developed larger body sizes, more quadrupedal stances, and more complex teeth and jaws. Hadrosaurs emerged in the Late Cretaceous, evolving flared snouts (hence the name “duckbill,” though they didn’t actually have duck-like bills), dense batteries of teeth in their jaws, and in some cases, elaborate head crests.

Hadrosaurs have an incredibly rich fossil record, including many examples of complete skeletons, bonebeds, trace fossils, skin impressions, full growth series, and more. This wealth of evidence has allowed paleontologists to learn amazing details about these dinosaurs’ social lives. Some species are known to have lived in herds, and others are known to have nested in colonies and taken great care of their newborn offspring.

Perhaps the most incredible feature of hadrosaurs can be found in their jaws. They had dozens of small teeth that formed large tooth batteries whose chewing surfaces constantly replenished as they wore down. Between their complex teeth, their dense tooth batteries, and their flexible jaws, hadrosaurs had perhaps the most advanced chewing apparatus of any vertebrates (sorry, mammals!).

On group of hadrosaurs – the lambeosaurines – sported ornate head crests. These crests were almost certainly used for visual display, but they also had extensive and often convoluted nasal passages running through them. There have been many hypotheses to explain these unique structures, but the most prominent one is that they served as resonating chambers to amplify sounds that these animals made.

Learn more

GEOL 104 Dinosaurs: A Natural History – Ornithopods

Leonardo: the famous hadrosaur “mummy”

“Duckbills” weren’t duck-billed

Maiasaura, a model organism for extinct vertebrate population biology

Skull anatomy and crest function of hadrosaurs (technical, open access)

Function and evolution of hadrosaur dental battery (technical, open access)
Non-technical article about this study

VIDEO: Visualizing hadrosaur chewing mechanisms
VIDEO: Nasal chambers within Corythosaurus skull

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If you enjoyed this topic and want more like it, check out these related episodes:

• Episode 21 – Dinosaurs, an Introduction
• Episode 52 – Sounds of the Past (Fossil Bioacoustics)
• Episode 88 – The Evolution of Teeth

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