Fish Fossil in Minnekahta Limestone

July 23, 2009

Picture 028  
Photographer: David Brown
Summary Author: David Brown

While doing some landscaping at my home in Hot Springs, South Dakota, I discovered the palaeoniscoid fish fossil above in pallets of recently delivered limestone slabs. The rock was from a quarry that's about 3 miles (5 km) from my home. Note that the fish is exceptionally well preserved with scales, fins and skull features clearly visible. It's preserved in a 30 lb (13.5 kg) slab of Minnekahta limestone, which has been dated to 260-270 million years ago (mya). According to Dr. Jim Martin, executive curator of the South Dakota School of Mines and Technology, “What David found appears to be a palaeoniscoid fish, a primitive ray-finned fish, which was within the group that may have given rise to later ray-finned fish, such as herrings and minnows.” Palaeoniscolds lived in a shallow, brackish sea that covered much of what is now South Dakota approximately 270 mya. This fossil has been loaned to the South Dakota School of Mines for display in their Museum of Geology. Photo taken on July 29, 2008.

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