In 1975, the fossilized remains of a 35-ft mosasaur, the Prognathadon stadtmani, were discovered by fifteen-year-old Gary L. Thompson* near Delta, Colorado. These remains were excavated by a team of paleontologists from BYU soon after and have been kept in the stores of BYU’s Museum of Paleontology for decades.
Joshua Lively, a grad student from the University Texas, recently stumbled upon the remains and recognized that there might be more scientific value in the mosasaur fossils than previously considered.
“In science, there’s always a lot of serendipity,” said Lively.
Lively is currently conducting his PhD research on the evolutionary dynamics of North American mosasaurs in the Late Cretaceous Period. He came to Provo to collect some data on BYU’s specimen for the sake of thoroughness, but soon realized that stadtmani provided some unique clues about mosasaur diversification.
“It was a complete accident actually, just coming in to collect some data on the animal and realizing ‘well, this really deserves its own new paper,’” he explained. In fact, Lively realized that due to the uniqueness of the species and the fact that much more of the animal had been prepared for study since its original description in 1999, it might even need to be classified under a new genus.
The Prognathadon stadtmani specimen has characteristics in common with both primitive and more recent mosasaurs, making it a key link in the evolutionary chain of the family. Of particular interest is the structure of the quadrate bone, which is located in the jaw joint and is similar to the human ear. In more recent Prognathadon, the quadrate bone is fused to other bones in the jaw, but that fusion is not present in Prognathadon stadtmani.
Another difference was that BYU’s specimen was significantly larger than its predecessors. The average mosasaur before stadtmani was about fifteen feet long, with a jaw that measured about half a meter. Stadtmani measures thirty-five feet and has a jaw length of more than a meter—more than twice the size. While other mosasaurs were eating fish and shellfish, the stadtmani “could probably eat anything it could fit in its mouth,” said Lively.
Lively explained how this observational data is used. Just like a geneticist will take thousands of DNA or RNA base pairs and run them through a software that will produce an evolutionary tree, paleontologists run a similar analysis.
“We’re just limited in that we don’t have thousands of base pairs. We just have hundreds of anatomical features on the skeleton,” said Lively. A paleontologist will use 100-200 morphological characteristics and “run that through a computer program . . . and that gives us this branching family tree.”
Why does understanding the evolution of an ancient species matter today? The Late Cretaceous Period had a particularly warm climate, perhaps comparable to our current warming climate.
“We can look at evolutionary patterns in the Cretaceous Period and try to understand: do the same set of ecological and evolutionary laws carry over [to all] times of globally warm climate?,” said Lively. He hopes that evolutionary changes in animals like the mosasaur can be used to predict what might happen to today’s species if the planet continues warming. “We can use hot-house times as an analog for what the future of our planet may hold,” he said.
Some geologists will study periods of warm climate in earth’s more recent geologic past because these animals in these periods are more similar to the fauna found on earth today. However, Lively says that research in more recent warm eras, like the Paleocene or Eocene, may not be as relevant because these eras were immediately preceded by mass extinctions. The Cretaceous Period is an important era to study because it had a much more mature global ecosystem, similar to our ecosystem today.
As a more personal message, Lively wants Utah residents to know that “the collection at BYU is really special. . . . It’s a neat point of pride for a university when you have such a great collection like that.” (Visit http://geology.byu.edu/museum to check out BYU’s Paleontology Collection)
*In May 2017, the CPMS article “Mosasaur: Died in cretaceous period, found in 1975, displayed in 2017” stated that Craig Slover was the original discoverer of the mosasaur fossil. Upon further investigation, documents indicate that Gary Thompson discovered the fossil.
—Lia Ludlam, College of Physical and Mathematical Sciences