Fossil Friday – Mistaken Identity

Femora

On March 8 Fossil Friday, I posted an 80-million-year-old dinosaur bone from New Mexico, which I identified as a tibia (shin bone). At the time, it was only partially prepped, and since then, WSC volunteer Joe Reavis has been working tirelessly to remove the remaining mudstone.

It turns out the “tibia” is actually a femur! It’s the proximal half of the left femur of a hadrosaur, one of the large duck-billed plant-eating dinosaurs that are so abundant in Upper Cretaceous rocks throughout the American West. Comparison with a complete hadrosaur femur from Montana (Museum of the Rockies specimen MOR 794) allows us to identify several major features, including the head that fitted into the hip socket and the 4th trochanter, a major muscle attachment site. It also shows that the WSC femur is from a fairly large individual, probably close to 30 feet long.

Hadrosaur bones are very common in the Menefee Formation, the rock layer in which this femur was collected by my colleagues from the Zuni Dinosaur Institute for Geosciences and Southwest Paleontological Society in 2015. We’ll have more to say in the near future.

Post by Curator Dr. Andrew McDonald

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