Thompson, Ida. (1979). Errant polychaetes (Annelida) from the Pennsylvanian Essex fauna of northern Illinois. Palaeontographica Abteilung A Palaeozoologie-Stratigraphie. 163(Lfg. 4-6): 169-199, 7 plates.
Errant polychaetes (Annelida) from the Pennsylvanian Essex fauna of northern Illinois
Palaeontographica Abteilung A Palaeozoologie-Stratigraphie
163(Lfg. 4-6): 169-199, 7 plates
World Polychaeta Database (WPolyDb)
The Essex Fauna is the marine phase of the Maxon Creek beds; soft-bodied animals, including the polychaetes, are preserved as whole-body fossils in siderite concretions within the Francis Creek Shale. Descriptions of the polychaetes include details of the jaws, setae, prostomia, cuticles, and cirri. Nine of the species are placed in the order Phyllodocida, extant families Aphroditidae, Hesionidae, Phyllodocidae, Nephtyidae, and Glyceridae, and the new family Fossundecimidae. One species is placed in the order Amphinomida, extant family Amphinomidae. The Essex polychaetes comprise the earliest (and only Paleozoic) record for all the families. For the families Hesionidae, Nephtyidae, and Fossundecimidae this is the only fossil record.
As a group, the polychaetes were large, active, predaceous, and epifaunal. This contrasts with Recent polychaete faunas on soft bottoms, where the dominant polychaete type is a sedentary deposit feeder. Possible reasons for this difference are discussed, none proving entirely satisfactory.