Nodocephalosaurus kirtlandensis: Dinosaur Migration
Size: 15 feet (4.5 meters)
Time Period: The Early Maastrichtian Stage of the Late Cretaceous.
Locale: The lower Kirtland Formation of New Mexico.
Name: “Knob-headed lizard.”
Ankylosaurs were perhaps the classic armored dinosaurs. Maybe Stegosaurus and kin get a bit more press, but the ankylosaurs were a bit more long-lived and heavily armored. They were around since the Late Jurassic, living side by side with their predecessors, who may have even been driven to extinction by them. They dominated the earth, particularly Laurasia, for most of the Cretaceous, and were especially successful because of their protective armor. I’ve covered Minmi, a distant cousin of Nodocephalosaurus, in the first post of my Dinodissertations series, and it, like Nodocephalosaurus, had important geographical implications.
The fauna of Western North America and Eastern Asia during the last stages of the Cretaceous Period were very similar, hinting at repeated migrations from one continent to the other. With the exception of the therizinosaurs, most groups present in one of these areas were also present in the other. Note: Chasmosaurine ceratopsians were not very widespread in Late Cretaceous Asia to our knowledge, but this may change following later remains. This was likely due to consistent migration from one area to another, and these movements have been happening since the Early Late Cretaceous, where creatures like Nothronychus and Zuniceratops were present in both places.
Nodocephalosaurus seems to have been the representative of an ankylosaurian movement from Asia to America, and was morphologically similar to Tarchia and Saichania, two other large ankylosaurs from Asia. It shows that even very late in the Cretaceous, migrations back and forth from Asia and North America were frequent. Saurolophus is another example of such migrations, because it has been found in Mongolia and the United States.
Nodocephalosaurus may have belonged in a family with Tarchia and Saichania, but some disagree, saying that it should just be given a classification as an Ankylosauridae incertae sedis. Whatever the case, the animal remains one of the most striking examples of faunal similarities between joined continents in the Latest Cretaceous, when the world as we know it did not yet exist.