Early and Middle Cambrian Hyolitha (Mollusca) from northeastern China

Abstract

The hyolithid species Hyolithes crebescens Resser and Endo, Hyolithes cybele Walcott, and Hyolithes delphus Resser and Endo from the Middle Cambrian of China are assigned respectively to the genera Nevadotheca Malinky, Novakotheca n. gen., family Hyolithidae, and Crestjahitus Syssoiev, family uncertain, all in the order Hyolithida. Recognition of Nevadotheca extends its geographic range from North America to China, and the occurrence of Crestjahitus in the Middle Cambrian of China increases its geographic and stratigraphic distribution from the Early Cambrian of the Soviet Union.Poor preservation of the type specimens of Hyolithes? aliger Resser and Endo, H.? aplatus Resser and Endo, H.? cariniferus Resser and Endo, H.? daphnis Walcott, H.? delia Walcott, H.? endoi Howell (as H. ornatus Resser and Endo), H.? mantouensis Resser and Endo, and H.? tenuis Resser and Endo renders their generic identification uncertain. Hyolithes (Orthotheca) glabrus Resser and Endo is here transferred to the hyolith order Orthothecida Marek and referred with question to Decoritheca Syssoiev, family Novitatidae.Morphology of the types of “Hyolithes” fuchouensis Resser and Endo, “H.” kuantungensis Resser and Endo, “H.” sondai Resser and Endo, “Orthotheca” daulis Walcott, and “O.” doris Walcott does not support assignment to the Hyolitha for these species; their phylogenetic affinity is uncertain.