摘要 : The dynamics of morphological change in the Early Permian ammonoid family Paragastrioceratidae is analyzed. Based on this analysis, the history of the evolution and distribution of this family is reconstructed and evolutionary tre... 展开 The dynamics of morphological change in the Early Permian ammonoid family Paragastrioceratidae is analyzed. Based on this analysis, the history of the evolution and distribution of this family is reconstructed and evolutionary trends are recognized, suggesting a new taxonomic system for this group. Three subgenera are recognized within Paragastrioceras: Paragastrioceras Tchernow, 1907; Stenogastrioceras subgen. nov.; and Pachygastrioceras subgen. nov. The genus Uraloceras is subdivided into four subgenera: Uraloceras Ruzhencev, 1936; Vetturaloceras subgen. nov.; Ramiuraloceras subgen. nov.; and Clausiuraloceras subgen. nov. A history of the relationships of paragastrioceratids with other families of Asselian-Artinskian ammonoids in the South Urahan basin is discussed in terms of general morphological diversity. Ecological interpretations are suggested for some events in the morphological evolution of the Early Permian ammonoids, primarily paragastrioceratids. 收起