Jaw-bearing polychaetes of the Silurian Eramosa Lagerstatte, Ontario, Canada
Peter H. von Bitter
Summary, in English
The Wenlock (middle Silurian) Eramosa Lagerstatte of the Bruce Peninsula, Ontario, Canada, is becoming known for its rich and diverse faunas, different preservational styles, and a combination of soft-body preservation associated with shelly body and trace fossils. Sampling for scolecodonts-the jaws of polychaete annelids-has yielded unique material. Hindenites parkheadensis new species is described from abundant specimens, including apparatuses, from a monospecific fauna that has allowed the complete dorsal maxillary apparatus to be reconstructed. The new species was recovered by acid digestion of carbonates, which are interpreted as having been deposited in shallow, marginally marine environments; the species may become a useful paleoenvironmental indicator, and the occurrence of Hindenites at Park Head, Ontario, is the first record of the genus outside of Baltoscandia. Bedding-plane material from Wiarton, Ontario, reveals a more diverse fauna of seven to nine additional polychaete taxa, most belonging to Kettnerites and Oenonites. Strata at Wiarton are interpreted as having been deposited in environments with good water circulation and open-marine conditions. The faunal composition of Eramosa polychaetes varied between localities of the Lagerstatte outcrop belt, supporting previous interpretations of differences in environment and/or taphonomic history. The relative abundance of scolecodonts suggests that jaw-bearing polychaetes played a significant role in the biotas that are now preserved in the Eramosa Lagerstatte. Moreover, the results underpin the notion that different polychaete species had variable environmental preferences and tolerances during the Silurian, and that polychaetaspids and paulinitids formed two of the most common and widely distributed families.