STL Science Center

STL Science Center

15 December 2012

Cretaceous Cows

Courtesy State of New Jersey
I think it is funny that Hadrosaurus, as are Hadrosaurs in general as a family, is thought of, maybe just by myself and no one else, as Cretaceous Cows. Cattle never roamed the earth in such a way as did animals like Edaphosaurus and Hadrosaurus, as great enormous herds, but were in more manageable numbers even before domestication and selective breeding gave us the cattle we see herded in cowboy movies and, in Kansas, lying around in milo fields (what some call grain sorghum). Hadrosaurus was obviously much larger than a cow, but as far as large herbivorous dinosaurs go, it was as cow-like as any dinosaur could be. The small section of the jaw and teeth that were included in the type fossils were indicative of an intense battery of vegetation grinding teeth, as seen in so many other Hadrosaurs, and are quite similar to the teeth (molars especially) of cattle. Why am I so adamantly comparing cows and Hadrosaurus?

Courtesy of Walters and Kissinger Complete Dinosaur Art Studio
The reason is that, all fleshed out, and with a dental array that is like a cow (except for the front teeth because Hadrosaurus had a keratin rich beak), Hadrosaurus was an animal that, in its ecosystem, held the same niche responsibility as cows do in our ecosystems. Cows are invasive, though we do not think of them as such, in many lands, so maybe a more just comparison is between Hadrosaurus and Bison, which would have held a similar niche as Hadrosaurus during the prime of their day in the Great Plains of North America. The herds of Bison probably rivaled the numbers of the Hadrosaurus herds during the Cretaceous also.  Additionally, for comparison, Hadrosaurus is one of the least ornamented of the Hadrosaur family; this can be partially explained by the fact that not many remains of the skull have been found either, leading to a lack of any evidence of ornamentation. This lack of skull has actually led to many considering a nomen dubium or a name that is no longer valid because it cannot be more clearly classified within the Hadrosaur family.

Permission pending artist approval
I think that all that might be missing from the skull, should we discover a complete skull, is ornamentation that further classifies Hadrosaurus. Personally, I hope that if anyone ever discovers a complete skull that it has absolutely no ornamentation, such as we have seen today in the illustrations. I think Iguanodon is lonely in the Hadrosaurs (for everyone: Iguanodon does belong to the Hadrosauriformes clade within the Ornithischia despite being in its own family) because it has no ornamentation and, other than maybe Parasaurolophus, it is the first dinosaur many people think of when they hear "duck-bill" or "Hadrosaur" in a conversation. Hadrosaurus, plain or later discovered to have some kind of interesting skull adaptation, is for now, one of the greatest and earliest discovered Cows of the Cretaceous.

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