Panamanian Fossil Record of the Killer Cone Shells

by Jonathan R. Hendricks, Associate Professor of Geology, San José State University

Much of my research focuses on the fossil record of cone snails in tropical America. Cone snails are truly remarkable animals. All are venomous predators (the stings from some fish-each species such as Conus geographus have led to human fatalities), many have intricately patterned shells, and the cone snail family (Conidae) is represented by over 700 living species, making it one of the most diverse groups of marine animals alive today. To put that number in perspective, there are around 5,400 living species of mammals and these are divided among over 150 different families. I am interested in understanding how modern cone snails became so diverse by using the fossil record to unravel their evolutionary “backstory,” especially their responses to ancient environmental changes.

The rich Neogene fossil record of tropical America presents an excellent opportunity to do this. While there are about 100 species of eastern Pacific and western Atlantic cone snails alive today, far more species have been described from the rich fossil record of this region (especially Florida and the Dominican Republic). While many species have been described, however, their connections to the modern fauna remain poorly understood. Some of my earlier work on fossil cone shells from the southeastern United States showed that some modern lineages have fossil records extending back in time about 3 million years; that is not entirely surprising, however. Recent work that I did on 5-6 million year old fossil cones from the Dominican Republic showed a similar pattern. Do some modern lineages have histories that extend even further back in time? Further, what is the biogeographic history of cone snails in this region, including their evolutionary responses to the closure of the Central American Seaway as a result of the rise of the Isthmus of Panama?

The Miocene Gatun Formation of Panama presents an opportunity to help answer these questions. The shells from the Gatun are very well preserved and some even show evidence of their original coloration patterns when exposed to ultraviolet light. I was thus very excited to be offered the opportunity to conduct fieldwork in Panama as a researcher participant in this year’s GABI-RET, not only to get a chance to collect fossil cone snails from the Gatun, but also to visit and learn about the paleontology of other rock formations in Panama and work with teachers in the field.

We collected a lot of fossil cone shells from two different Gatun Fm. localities (San Judas and Sabanitas) on July 24 (both of these exposures of the Gatun Fm. are ~10 million years old). I was very fortunate to have so many teachers and researchers on the lookout for cone snail fossils; their hard work in the field resulted in a fantastic new collection of shells.

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A fossil cone shell awaiting collection from the Gatun Formation. Photo by Jonathan Hendricks.

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The fossil cone shells we collected from the Gatun Fm., washed and ready for packing. Photo by Jonathan Hendricks.

 

The shells that we collected were transferred to the Florida Museum of Natural History and then fumigated, bleached, washed, and catalogued. I received them on loan from the FLMNH last week and have begun my research on them. One of the first things that I did upon receiving the loan was to put the shells under an ultraviolet light to see if their original coloration patterns fluoresce, as was the case in the much younger fossils that I have studied. I am excited to report that nearly every single cone shell that we collected from the Gatun fluoresces and shows evidence of its original pigmentation pattern. In total, we collected 9 different species of cone snails on July 24. Perhaps even more interestingly, some of these species show clear connections to cone snails alive today. As such, I expect that documentation of the shells that we collected will provide important temporal information for understanding the evolutionary history of cone snails in tropical America. I am planning to present my initial findings on this research at the 2015 Annual Meeting of the Geological Society of America in Baltimore in early November.

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Almost all of the fossil cone shells that we collected show preservation of their original coloration patterns, which fluoresce when exposed to ultraviolet light. This image shows the variation in coloration pattern of one of the species that we collected. Photo by Jonathan Hendricks.

While I enjoyed my participation in the GABI-RET from a purely research-driven standpoint, I enjoyed it just as much for the opportunity it presented to work firsthand with teachers. One of my favorite days of the trip was the one spent working with the teachers on lesson plan development at the BioMuseo. It was an energizing day and it was wonderful to learn how the teachers planned to incorporate their experiences in the field and what they had learned about the natural history of Panama with their students. Their passion for teaching was infectious and I could not help but come away from the day eager to get back into the classroom myself. Their enthusiasm throughout the trip encouraged me to think about new ways in which I might also share what we learned in Panama with my own college-level students and I think the experience will leave a lasting imprint on my teaching as well.

 

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