Stan Beeman is in an HBO series.
Clarkoceras is a genus of breviconic ellesmerocerid cephalopods , one of only two genera known to have crossed from the Late Cambrian , Trempealeauan , into the Early Ordovician , Gasconadian .. ellesmerocerid. Ellesmerocerida. Cambrian. Cambrian. Ordovician. Ordovician. Gasconadian. Gasconadian Stage. -LRB- Flower 1964 , Teichert 1988 -RRB- ; the other being Ectenolites .. Ectenolites. Ectenolites