Duck-bill Dinosaurs Had More Advanced Teeth Than Cows or Horses

Posted on October 7, 2012

A team of paleontologists and engineers have discovered that duck-bill dinosaurs (hadrosaurids) had teeth more complex than those of modern plant-eaters, such as cows and horses. The study is published here in the journal, Science.

Hadrosaurids were the dominant plant-eaters during the Late Cretaceous about 85 million years ago. They had broad jaws with as many as 1,400 teeth. They were previously thought to have teeth similar to reptiles with only two tissue types (enamel and othodentine), but paleontologists have long suspected the teeth were more complex and unusual.

Mark Norell, chair of the American Museum of Natural History's Division of Paleontology and an author on the paper, said in a release, "We thought for a long time that there was more going on because you could just look at the surface of the tooth and see advanced topography, which suggests that there are many different tissues present."

Norell worked with lead author Gregory Erickson, a biology professor at Florida State University, to examine the hadrosaurid teeth in depth. Erickson sectioned the fossilized teeth and made microscope slides from them. These slides revealed that hadrosaurids actually had six different types of dental tissues - four more than reptiles and two more than modern mammal grinders like horses, cows, and elephants. In addition to enamel, orthodentine, secondary dentine and coronal cementum, which are found in mammal grazers, the hadrosaurid teeth also have giant tubules and a thick mantle dentine. The researchers say the extra tissues probably helped provide protection from abscesses.

Erickson describes hadrosaurids as "walking pulp mills." He says, ""We were stunned to find that the mechanical properties of the teeth were preserved after 70 million years of fossilization."

Norell says, "Duck-bills' advanced tissue modification appears to have allowed them to radiate into specialized ecological niches where they ate extremely tough plants like fern, horsetail, and ground cover that were not as easy for dinosaurs with shearing teeth to eat. Their complex dentition could have played a major role in keeping them on the planet for nearly 35 million years."

DINOSAURS