Reassembling a fossil skeleton is sometimes said to be like putting a puzzle together. It’s not an inaccurate analogy, but there are some significant differences. For example, you can never be totally sure what the animal is going to look like when you start. There’s no box to tell you what the end result should be. Sure, the basics of anatomy can help you differentiate between tooth, vertebra, femur, and other pieces, but if paleontologists don’t pay meticulous attention to all the parts, they might create a chimera of bones that don’t really fit together. That’s how celebrated fossil hunter Barnum Brown created a fossil monster.

A sketch of Brown’s “Megadontosaurus”. Reproduced in Norell et al., 1995.

In 1933, while looking for dinosaurs in the desert of Wheatland County, Wyoming, Brown stumbled across the delicate bones of a small theropod dinosaur. There were pieces of the spine, legs, arms, and hips from an animal that wouldn’t have been more than four feet in length, and scattered among them were huge teeth. The serrated, curved slicers were huge for an animal this size – bigger than its claws – but, because they were found so close to the other bones, Brown reasoned that they must have gone together. The dinosaur must have had a disproportionally huge head to house such teeth, and, as he studied the bones, he had sketches made depicting what he informally named “Megadontosaurus” – the “huge-toothed lizard”.

Brown never got around to publishing his find, though. As with other dinosaurs he recovered from the 110 million year old rock of Wyoming and Montana, “Megadontosaurus” was left to hang in scientific purgatory as Brown worked on other projects and, ultimately, passed away. It wasn’t until 1970 that paleontologist John Ostrom – who was studying the dinosaurs of the same formation “Megadontosaurus” came from – had another look at the material and realized that Brown had mixed up two different dinosaurs.

A reconstruction of Microvenator. Art by Jaime A. Headden, CC BY 3.0.

The partial skeleton Brown found was from a little theropod dinosaur never seen before – which Ostrom named Microvenator – while the teeth belonged to Deinonychus, a much larger predatory dinosaur that Ostrom had named in 1969. In fact, Brown had also found the remains of Deinonychus in 1931 – which he was planning to name “Daptosaurus” – but didn’t realize the connection between those bones and the “oversized” teeth. There were so many dinosaurs to study and describe that Brown apparently got caught up in the rush and didn’t carefully look his dinosaurs in the mouth.

Reference:

Norell, M., Dingus, L., Gaffney, E. 1995. Discovering Dinosaurs. Berkeley: University of California Press. pp. 126, 129