Templeton Thunderegg with Brown Stained Matrix

There are subtle differences between this and the specimens known to come from the Highway 46 bed (hints of radial fracturing and no circumferential banding in the matrix), which leads to speculation that this is closer to the Biconoid thundereggs, even though it doesn't have a biconoid core.

11 cm x 9 cm

From the collection of Mark Ketsdever