A new University of Michigan study of dinosaur fossils from India has revealed that the sauropod dinosaur Kotasaurus yamanpalliensis wielded a bony tail club.
The research was based on the discovery of four ellipsoidal skeletal elements collected from the Kota Formation of the Pranhita-Godavari Valley of southcentral India, offering insights into these extinct giants.
The research team compared these Kotasaurus tail clubs, estimated to be 175 million years old and housed in Hyderabad's Geological Survey of India (Southern Region) offices, to structures found in similar-aged sauropods from China, Shunosaurus lii and Omeisaurus tianfuensis. Notably, the complete tail of Shunosaurus allows for detailed morphological comparisons that shed light on the evolutionary trajectory of tail clubs among early sauropods.
"Our analysis indicates that the tail clubs may consist of up to three individual vertebral elements that fuse together as the dinosaur matures," said lead author Tariq Abdul Kareem, U-M graduate student in the Department of Earth and Environmental Sciences. "This finding not only enriches our understanding of Kotasaurus but also raises intriguing questions about the evolutionary origins and function of these structures."
Using computed tomography scans, the researchers examined the internal architecture of the Indian tail clubs, revealing growth lines and unique features whose origins and functions remain a mystery. The similarities in morphology and the temporal range of the Indian and Chinese tail clubs prompt further investigation into whether these traits evolved independently or represent a feature shared among basally diverging sauropods.
"This discovery underscores the importance of the Kota Formation in piecing together the early evolutionary history of sauropods," said Jeffrey Wilson Mantilla, U-M professor of earth and environmental sciences and curator of the university's Museum of Paleontology. "It helps us to reconstruct late stages of the transition between the earliest dinosaurs, which were small and bipedal, and the iconic sauropods, which were large and quadrupedal."
Wilson Mantilla first examined the Kotasaurus collection during a six-week visit in 2001, when he had the opportunity to meet and work with the late P. Yadagiri, of the Geological Society of India, who first discovered and described the species. Wilson Mantilla has long been fascinated by the Indian tail clubs and their implications for early sauropod evolution.
"I was looking for a way to work with dinosaur fossils from India," Kareem said. "When Jeff suggested this and talked about his prior work in 2001 to me, I knew it was an immediate fit."
Kareem traveled to India in 2018 and spent a month studying tail clubs for this study.
"Taking the four tail clubs in a taxi to a local hospital for a CT scan was an adventure in itself," he said.
The findings, published in the Journal of Vertebrate Paleontology, will contribute significantly to ongoing discussions in paleontology regarding the adaptive functions of tail clubs in sauropod dinosaurs.
