July is off to a good start … academically speaking … for Morgan Churchill, an assistant biology professor at the University of Wisconsin Oshkosh.
The vertebrate paleontologist is an author on not one but two research papers published this week in high-impact, peer-reviewed journals.
First, a paper that describes a new type of giant predatory dolphin fossil appeared Thursday in Current Biology, a biweekly scientific journal that emphasizes research on molecular biology, cell biology, genetics, neurobiology, ecology and evolutionary biology.
Second, a study that examined 172 toothed whale skulls to quantify cranial asymmetry and reconstruct the evolutionary history of the aquatic mammal was published today in BMC Biology, an open access journal featuring outstanding research in all areas of biology.
“I’ve never had this type of week before,” said Churchill, who has taught undergraduate human anatomy at UWO since joining the biology faculty in 2017.
Both studies contribute to the understanding of whale and dolphin evolution, two closely related marine mammals. In fact, all dolphins are whales but not all whales are dolphins.
“Whales capture our attention as they are very intelligent and have become the ‘poster children’ for environmental causes and endangered species,” he said. “Whales also have an excellent fossil record, making them icons of evolution.”
Churchill’s overall research program focuses on examining how marine mammal morphology has adapted to an aquatic lifestyle over time and how changes in morphology have influenced diversity and evolution in the group. Morphology is the study of size, shape and structure of animals, plants and microorganisms.
In the Current Biology article, Churchill and colleagues at the College of Charleston, New York Institute of Technology and Wellesley College report the nearly complete skeleton of the extinct large dolphin, Ankylorhiza tiedemani, from South Carolina.
“This new specimen fills in important anatomical information on the early evolution of locomotion in whales, as well as reveals the ecological diversity in whales that was already present 24 million years ago,” Churchill said.
As second author on the study, Churchill carried out the anatomical analyses and collaborated on interpreting the results and writing the paper.
Ankylorhiza is not a member of any group of whales living today but rather is closely related to the common ancestor of all toothed whales.
“Evidence from its anatomy suggests it was an apex predator, perhaps filling a niche today occupied by the killer whale, Orcinus orca,” Churchill said.
Ankylorhiza preserves a relatively primitive vertebral column and flipper, indicating that simplification of limbs and vertebrae evolved independently in baleen whales (also known as whalebone whales) and toothed whales.
“The most important finding of this study is that we provide evidence that adaptations for underwater locomotion evolved separately in these two major groups of whales alive today—baleen whales and toothed whales—likely due to similar functional demands,” Churchill said. “This highlights an excellent example of convergent evolution, as well as reveals that whale evolution is much more complicated than we thought.”
In addition, this new specimen shows that even early in their evolution, toothed whales showed a high degree of diversity with different species adapting to different lifestyles and diets, he said.
Toothed whales also have some of the “most bizarre skulls” of any mammal group, Churchill said.
“Much of this weirdness is due to the high levels of bilateral cranial asymmetry present in the skull,” he explained. “In most animals, the bones that make up the face are the same size for both the right and the left halves of the skull. However, in many whales, bones on the right side of the face are much larger than those on the left.”
Although remarkable, the feature has been poorly studied and not rigorously quantified in fossil whales.
For the study reported in the BMC Biology article, Churchill was part of a team of researchers led by Ellen Coombs from University College London and the Natural History Museum in London.
For his part, Churchill provided a large number of 3D scans of the whales collected from museums during a post-doctoral project.
The research showed that the cranial asymmetry is likely due to development of echolocation—the ability to locate objects by reflected sound—in the toothed whales.
“This research highlights a major evolutionary change in one of the best examples of evolution,” Churchill said. “It provides the first exhaustive quantification of cranial asymmetry in whales, traces its evolution and ties the changes with asymmetry to the development of new adaptations and changes in the environment.”
Churchill’s research lab at UWO has been a training ground for undergraduate biology students. In fall 2020, a graduate student will be joining the team.
- Convergent Evolution of Swimming Adaptations in Modern Whales Revealed by a Large Macrophagous Dolphin from the Oligocene of South Carolina
- Wonky whales: the evolution of cranial asymmetry in cetaceans
- UWO biologist part of team that discovers ‘megalodon’ shark went extinct much earlier than previously thought
- UWO biologist helps identify new ancient, toothless dwarf dolphin
- Study biology at UW Oshkosh