From place to place and year to year, it is a fact of paleontology that some of the best discoveries are made at the very end of the field season. This is not so common that it is some kind of natural law, but it happens quite often, and there is more to it than just luck.
In order to find the fossils they are after, paleontologists must develop a "search image" of what the fossils at a particular place look like and become familiar with the local geology. This fossil intuition takes some time to acquire. By the time fossil hunters are well-versed in the intricacies of the local strata, it is often the end of the season!
Such was the case with the discovery of a nearly complete Dimetrodon skeleton by the Houston Museum of Natural Science (HMNS) field team in Baylor County, Texas. Dimetrodon, despite its reptilian appearance, was not a dinosaur. Not even close. An apex predator during the middle of the Permian (about 280 to 265 million years ago), Dimetrodon was a synapsid—it belonged to a group of vertebrates entirely represented by mammals today. As odd as it might seem, Dimetrodon was actually one of our distant, extinct cousins and not a reptile at all.
According to the museum's associate curator of paleontology, Dave Temple, the team had been finding bits and pieces of the animal during the field season but did not stumble onto the articulated skeleton until the day before they were due to return home. They were very fortunate to have located it. This specimen has an articulated rib cage, spine and sail, with the skull resting near the rest of the body. The discovery of the animal's head, especially, is significant as it appears to represent a species, Dimetrodon giganhomogenes, that has been headless since it was first described over a century ago.
The HMNS has big plans for this fossil, nicknamed "Wet Willi." Even though many Dimetrodon skeletons have been found in Texas, the HMNS does not have one of these animals on display. Once cleaned up and put back together, Willi will be put on exhibit in the museum's renovated fossil hall, which is due to open in 2012.
For more on Willi and the scientific work being done at the HMNS, check out the Beyond Bones blog.