The intriguing journey of a remarkable fossil began in 1999 when Dr. Richard Köhler made a significant discovery during a research expedition on Pitt Island in the Chatham Islands. While traversing the island's western coastline near Waihere Bay, he spotted a three-dimensionally preserved, mummified fish fossil embedded in a steep cliff, challenging to access.
To retrieve it, Köhler embarked on a 3km trek back to his lodging in Flowerpot Bay for a ladder. Upon his return, he carefully extracted the fossil, which was encased in several hefty blocks.
Upon his return to Dunedin, he presented the specimen to the University of Otago's Department of Geology. Emeritus Professor Daphne Lee recalls that she and the late Professor Ewan Fordyce recognized its exceptional significance immediately. "It was quite unlike any other fish fossil known from Aotearoa, New Zealand," Lee stated.
Identification of a Remarkable Ancient Predator
After meticulous preparation by the late fossil preparator Andrew Grebneff, the fossil garnered attention from Professor Mike Gottfried, a fossil fish expert from Michigan State University. Having previously collaborated with Ewan on studies involving New Zealand's fossil fishes and sharks, Gottfried began an investigation into this unusual specimen.
Researchers ultimately identified the 1.2-meter-long mummified fish as a tarpon, a species that no longer inhabits New Zealand waters. Modern tarpons are known as large predatory fish that consume smaller fish whole, a behavior suggested by the fossil's anatomy. Its elongated body, robust scales, powerful tail fin, and large upward-facing mouth indicate it was an active predator at the top of its food chain.
Missing Information Hinders Research
Despite the fossil's significance, researchers encountered a major challenge due to the absence of critical geological information regarding the discovery site, compounded by the passing of Richard several years prior.
As Ewan passed away in November 2023, a draft scientific paper had been prepared, yet the study stalled due to the lack of detailed field information needed for proper documentation of the fossil's discovery location.
A breakthrough occurred in early 2025 when one of Richard's children, studying at Otago, sought photographs of his father. After meeting with Daphne, Richard's family generously donated his field notebooks, including those from the original Pitt Island expedition.
"This enabled us to gather enough specific locality information to prepare a Fossil Record Form and scientifically catalogue the fossil," Daphne explained.
New Fossil Species Named
The completed study was recently published in the New Zealand Journal of Geology and Geophysics, marking the first report of a high-in-the-food-chain predatory bony fish from Paleogene-age rocks (approximately 55 million years ago) in Aotearoa. The fossil has been named Ikawaihere koehleri in honor of Richard Köhler and the discovery location, with acknowledgments to Heidi Lanauze and the Hokotehi Moriori Trust for their approval of the name.
Mike expressed his privilege in working on this "remarkable fossil," noting its contribution to understanding the evolutionary history of tarpons and its unique features preserved in exquisite 3D detail. Daphne shared her delight in the study's completion, emphasizing that it serves as a fitting tribute to Richard, Ewan, and Andrew, and expressed gratitude to Richard's family for their invaluable contribution.