The Winterset Limestone member of the Dennis Formation was deposited in fairly shallow well-oxygenated water. Most of the invertebrate fossils in the Winterset limestone are large are large and have fairly ornate shells. The base of the Winterset limestone was deposited in much deeper water than the top of the Winterset and systematic collecting through this sequence will demonstrate this.
Isogramma millepunctata
Description: "Isogramma millepunctata" (Meek & Worthen) is a relatively rare brachiopod. It has been found only in a few sites in the midcontinent. It may be found in large numbers when it is found but its distribution is sporadic although it is long-ranging, from the middle Pennsylvanian (Desmoinesian) through the early Permian (Wolfcampian). This species is characterized by the very distinct and evenly spaced lirae on the shell. The triangular muscular platform is on the pedicle valve and is very characteristic for this genus. The relationships of Isogramma is not well understood but it is similar to chonetoid brachiopods in many features. Images by Ed Schafer; Specimens from Bill Rushlau.
Isogramma millepunctata
Description: "Isogramma millepunctata" (Meek & Worthen) is a relatively rare brachiopod. It has been found only in a few sites in the midcontinent. It may be found in large numbers when it is found but its distribution is sporadic although it is long-ranging, from the middle Pennsylvanian (Desmoinesian) through the early Permian (Wolfcampian). This species is characterized by the very distinct and evenly spaced lirae on the shell. The triangular muscular platform is on the pedicle valve and is very characteristic for this genus. The relationships of Isogramma is not well understood but it is similar to chonetoid brachiopods in many features. Images by Ed Schafer; Specimens from Bill Rushlau.