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''Hedbergella'' is a planktonic foraminiferal genus from the Cretaceous, described by Loeblich and Tappan, 1961, as : Test free, trochospiral, biconvex, umbilicate, periphery rounded with no indication of keel or poreless margin; chambers blbular to ovate; sutures depressed, radioal, stright or curved; wall calcareous, finely perforate, radial in sturucture, surface smooth to hspid or rugose; aperture an interiomarginal, extgraumbilical-umbilical arch commonly bordered above by a nnarrow lip or spatulate flap, ... Includes species otherwise similar to ''Praeglobotruncana'' but which lack a keel or poreless margin, hence is regarded as a separate genus rather than as a subgenus of ''Praeglobotruncana'' as by Banner and Blow (1959). ''Hedbergella'' was named by Brönnimann and Brown, 1958, and is included in the Rotaliporacea according to Loeblich and Tappan (1988), which is the Rotaliporidae of Loeblich and Tappan (1961) and the Treatise Part C, on Prosista 2. ''Hedbergella'' ranges through most of the Cretaceous, from the Hauterivian to the Maastrichtian at the end. Among species included are those originally named ''Globigerina cretacea'' by d'Orbigny. ==Globigerina cretacea== ''Globigerina cretacea'' was originally named by d'Orbigny for trochoidal foraminifera with globular chambers found in Cretaceous marine sediments in the Paris Basin of France. Specimens found subsequently in other locations in Europe and the United States, especially in Texas, were assigned to the same species, although differences in size were apparent. Assignment to the genus ''Globigerina'' was based on the globular to ovate chambers and trochoidal coiling, however true ''Globigerina'' is limited to the Cenozoic. Globigeninoid (look like Globigerina) forms from the Cretaceous differ in the placement of the aperture and nature of secondary apertures. Three species of ''Hedbergella'' were, on separate occasions, originally named ''Globigerina cretacea'': ''Hedbergella amabliis'' Loeblich and Tappan, 1961 and ''Hedbergella brittonensis'' Loeblich and Tappan, 1961, both holotypes rom the Britton Clay, Eagleford Group, in Dallas County, Texas, and ''H. delrioensis'', originally ''Globigerina cretacea var delrioensis'' Carsey, 1926, topotypes from within Austin, Travis County, Texas. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hedbergella」の詳細全文を読む スポンサード リンク
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