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Taxonomic revision of lower and middle Paleozoic Orthothecida (Hyolitha) from North America and China
Published online by Cambridge University Press: 14 July 2015
Abstract
North American and Chinese lower and middle Paleozoic representatives of the hyolith order Orthothecida are here placed in the families Orthothecidae Syssoiev, Novitatidae Syssoiev, Decorithecidae Syssoiev, Chelsonellidae n. fam., ?Isitithecidae Syssoiev, and ?Tchuranithecidae Syssoiev. The Orthothecidae is redefined, and the Decorithecidae is in part synonymized with the Novitatidae.
Re-examination of type specimens of some species formerly included in the order Hyolithida requires placement of these species in the order Orthothecida. The type suite of Hyolithes newsomensis Foerste from the Middle Silurian of Tennessee is divided into two species, and is used as a basis for the new genus Foersteotheca; the species F. merryi is new. Hyolithes richardi Clarke from the Lower Devonian of New York is designated as the type species of the new genus Devoniotheca. Orthotheca cyrene Walcott from the Middle Cambrian of China is now included under Decoritheca. Foersteotheca, Devoniotheca, and Decoritheca are here placed in the redefined family Novitatidae. Hyolithes vanuxemi Walcott is assigned to the new genus Chelsonella in the new family Chelsonellidae. The types of Hyolithes newtoni Walcott from the Upper Cambrian of South Dakota and Hyolithes canalis from the Middle Cambrian of China are both included under Decoritheca with question.
Recognition of orthothecid hyoliths in the Cambrian of North America and China provides a more accurate record of the geographic and stratigraphic distribution of this group. The discovery of Foersteotheca and Devoniotheca constitutes the first known middle Paleozoic orthothecid occurrences from North America. In addition, reports of Tchuranithecidae and Isitithecidae in North America, if authentic, are the first occurrences of these forms in North America. The discovery in North America of hyolith taxa previously known only from the Soviet Union and China raises the possibility of intercontinental correlation using these fossils.
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