Ghost Sharks in Kansas

Submitted by Deborah Cramer

Ghost Sharks in Kansas
Image of 300 million-year-old ghost shark skull
Photo © PNAS/Philippe Janvier (CNRS, Museum National d’Histoire Naturelle)

Some 300 million years ago, during the Pennsylvanian period, eastern Kansas, now about 1000 feet above sea level, was covered by a shallow ocean. “Ghost sharks,” also called iniopterygians, or chimaeras, swam in its muddy waters. These distant relatives of today’s sharks and ratfish had small bodies, large heads and eyes, shark-like jagged teeth, tails with clubs, and fins with spikes. Seemingly bizarre, they were common in the ocean back then. Now they are extinct.

Scanning a fossil unearthed over 70 years ago in Kansas, scientists using high-powered xrays (synchrotron holotomography) constructed a 3-D image of an iniopterygian brain case. They unexpectedly found a tiny brain inside, less than 1/3″ long, complete with an optic nerve. The animal’s large eyes may have compensated for its poor hearing.

Brains, being soft and watery, quickly decompose, making a fossil brain this old rare. Scientists think the fish may have been decapitated, its skull and brain fossilized by phosphate bacteria from the predator’s intestine.

References and more information

Fossil brain
http://www.amnh.org/science/papers/old_brain.php
Pradel, A., Langer, M., and Maisey, J. G., et. al. 2009. Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography. PNAS 106:5224-5228.

Map of ancient sea in Kansas 300 million years ago, late Pennsylvanian period
http://jan.ucc.nau.edu/~rcb7/namPP300.jpg

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