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What is a dinosaur paleontologist doing on a paper about Megalodon shark babies?

Updated: Jun 5, 2022

Megalodon (technically Otodus megalodon) was a giant (almost 50 feet long), extinct relative of great white sharks (the largest of which are less than 40 feet long). It lived approximately 20 million to 3.6 million years ago. Pictured below is a modern great white shark.

During the pandemic, it was difficult for me or many scientists to accomplish work in the lab due to COVD-19 restrictions and to protect our students, colleagues, and friends. It was during this time in 2020 that my long-time friend and colleague Kenshu Shimada at DePaul University reached out to me for help with a study he and others were conducting on the giant, extinct shark Megalodon.

Although I'm a dinosaur paleontologist, working on sharks is actually nothing new to me. First, I teach a comparative anatomy course where the students (many preparing for vet or med school) dissect spiny dogfish sharks as a means to learn the anatomy of a fishy vertebrate. Second, I had the honor of working with a gifted and enthusiastic undergraduate student, Katie Reiss, at my previous institution, Western Illinois University, on a paper where she and I studied the growth and shape changes in spiny dogfish tails from juvenile to adult. Third, Kenshu and I have for years talked about collaborating on a project together, although how a dinosaur and shark expert were going to do that remained to be seen.

Previously, Kenshu and his colleagues had already obtained CT scans (essentially hundreds of X-ray slices) of Megalodon backbones (vertebrae). These specimens are some of the best known fossils of Megalodon (discovered in the 19th Century in Antwerp, Belgium, and housed at the Royal Belgian Institute of Natural Sciences’ conservatories in Brussels). However, they needed someone with experience in analyzing CT scans to help extract biologically meaningful information from these data. Kenshu reached out to me because of my work using XROMM to analyze limb movements in mammals, birds, and reptiles which meant I knew how to do what was needed. Also, it helped us realize our goal of working on a project together ... finally! And, since this was 2020, we were able to stay safe and work remotely.

So, I was privileged to be part of a study, led by Kenshu Shimada, that has helped reveal the size of newborn Megalodon pups! My university has done a wonderful job of writing up the implications of the research, and I provide that link below (thank you, Susan Allen!).

In a nutshell, by examining the growth bands in one of the best vertebral specimens of the extinct shark Otodous megalodon (Megalodon), a relative of the great white shark that grew to 14-15 meters (nearly 50 feet) in length, we were able to estimate the size of the new born pups: 2 meters or approximately 6.6 feet long! O. megalodon is a member of the lamniform sharks (like the great white), and in all lamniforms the young hatch in utero and grow in part by eating unfertilized and sometimes fertilized eggs. That means growing Megalodon pups were likely practicing this same sibling cannibalism in the womb — whether that means they were eating hatched siblings is difficult to know.

Above, relative size of a newborn and adult Megalodon shark (based on the growth bands in this vertebral specimen, it was approximately 46 years old and approximately 30 feet long when it died). Tall (6.6 foot) human silhouette for comparison. This figure is a composite of figures and artwork by Kenshu Shimada and Matthew Bonnan.

Would you like to read the peer-reviewed article?

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Matthew F. Bonnan, Ph.D.

Paleontologist | Professor | Author | Science Communicator | Singer/Songwriter

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