Classification, phylogeny, and paleobiogeography of the new subfamily gifuellinae and a revision of the family neoschwagerinidae (Superorder Fusulinoida); guadalupian (Middle Permian)

摘要

The new subfamily Gifuellinae is composed of two genera, Gifuella Honjo and Gifuelloides n. gen., and is assigned to the family Neoschwagerinidae, superorder Fusulinoida (Foraminifera). This new subfamily is based on extensive and ongoing studies by Kobayashi of fusulinoid material from the Akasaka Limestone of Japan and a careful literature survey. In both Gifuella and Gifuelloides, the spiral wall consists of a uniform tectum and a very fine alveolar keriotheca, which forms a consistent, thin layer that gives rise to the septula. Both genera are characterized by relatively small proloculi. Of the two genera, species of Gifuella are simpler, smaller, and have fewer whorls and they have well-developed, thin, planar primary transverse septula and almost completely lack secondary transverse septula. Species of Gifuelloides are larger, have more whorls, and have only a few secondary transverse septula in their middle and outer whorls. Gifuella sp., previously recorded from Hyogo, Japan, is here named Gifuella harimensis n. sp. The new genus Gifuelloides includes its type species G. larga (Morikawa and Suzuki), and G. hanaokensis (Morikawa and Suzuki). The Gifuellinae differ from other neoschwagerinids assignable to the subfamilies Neoschwagerininae, Lepidolininae, and Sumatrininae in having differences in details of the spiral test wall, in lacking or nearly lacking secondary transverse septula, and in having relatively consistently sized proloculi (larger than those in Neoschwagerininae but smaller than in Lepidolininae and Sumatrininae), and in having a generally consistent, inflated fusiform test with a diameter-to-length ratio of 2:3. The Akasaka Limestone includes Middle Permian strata of Guadalupian age, which are equivalent to the Kubergandian, Murgabian, and Midian stages of the Tethyan faunal realm. Gifuellinae occur in the upper two of these stages: species of Gifuella are prominent in beds of Murgabian (Wordian) age and species of Gifuelloides are common in beds of Midian (Capitanian) age. Both genera of Gifuellinae occur exclusively in accreted terranes that were displaced around the northern Circum-Pacific during the Jurassic and Cretaceous (Japan, Koryak Terrane in northeastern Russia, and Washington State, USA). This distribution of Gifuella and Gifuelloides reinforces the concept of Kobayashi's paleobiogeographic Province C (Panthalassan Province) as an independent faunal province during the Middle Permian, originally based on the distribution of other neoschwagerinids. A number of authors previously considered Colonia Lee, from the Maokou Limestone, Guangxi, China, as a synonym of Gifuella, but both Gifuella and Gifuelloides differ significantly in test features from Colania. As restudied by Sheng, species of Colania have notably larger proloculi, a marked difference in size between microspheric and megalospheric individuals, and much more complete development of transverse and axial septula.