The Denver Museum of Nature & Science announces the addition of Tyler Lyson as curator of vertebrate paleontology.
Lyson studies fossil vertebrates, particularly dinosaurs and turtles. He is especially interested in the evolution of body plans and extinction patterns of different groups across major extinction events. He uses fossils to help determine how ecosystems change through time, what killed the dinosaurs, how long it takes for an ecosystem to normalize after a major extinction event, and the sequence of changes, such as a lizard-like animal becoming the highly modified body plan of turtles.
“Tyler brings exciting new talents to the Museum’s curatorial team,” said Dr. Scott Sampson, vice president of research and collections and chief curator. “He engages colleagues and citizen scientists alike in his research and explains discoveries in ways that intrigue and excite elementary students as much as or even more so than his peers.”
Prior to the Museum, Lyson was a Peter Buck Postdoctoral Researcher at the Smithsonian National Museum of Natural History. He is also the founder and director of the Marmarth Research Foundation, dedicated to promoting informal science education and scientific research among citizen scientists in the fossil-rich Hell Creek Formation in southwestern North Dakota.
“I look forward to going on field expeditions to help build the Museum’s collection of vertebrate fossils and to share my excitement about Earth’s rich history with the general public,” said Lyson.
Recent Research Leads to New Understanding of Turtle Evolution
Lyson’s research on the evolution of turtles and their shells, published this month in Nature Communications, has led to new understanding of how turtles developed their unique respiratory anatomy. Unlike other vertebrates that use a combination of musculature and bone to compress and expand the lungs to breathe, turtles rely on musculature alone.
Over time, the ribs of turtles have grown fixed into their rigid shells. However, even prior to this, turtles relied solely on trunk muscles for respiration. Lyson’s study sheds light on this unique feature among vertebrates as well as the process and timing of the evolution that occurred to set turtles apart.
By studying thin sections of the fossils, Lyson and colleagues have shown that the modern turtle breathing apparatus was already in place in the earliest fossil turtle, an animal known as Eunotosaurus africanus. This animal lived in South Africa 260 million years ago and shares many unique features with modern turtles, but it lacked a shell. A recognizable turtle shell doesn’t appear for another 50 million years.
Lyson says “The body plan of Eunotosaurus tells us what turtles looked like before they had a shell, which provides key insights into the evolution of both the iconic turtle shell as well as the unique breathing mechanism found in modern turtles.”
The study suggests that early in the evolution of the turtle body plan, a gradual increase in body wall rigidity produced a division of function between the ribs and abdominal respiratory muscles. As the ribs broadened and stiffened the torso, they became less effective for breathing, causing the abdominal muscles to become specialized for breathing. This in turn freed up the ribs—approximately 50 million years later—to become fully integrated into the shell.
The next phase of Lyson’s research will look into why the ribs of early turtles began to broaden, as this is the first step in the evolution of the ribs becoming integrated into the shell and a reliance on abdominal muscles for respiration.
Lyson received his PhD from Yale University, and is a member of the Society of Vertebrate Paleontology and American Society of Ichthyologists and Herpetologists and is a Honorary Researcher at the University of Witswatersrand in South Africa and Curatorial Affiliate at the Yale Peabody Museum.