Hedbergella

Hedbergella is a genus of planktonic foraminifera 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 globular to ovate; sutures depressed, radial, straight or curved; wall calcareous, finely perforate, radial in structure, surface smooth to hispid or rugose; aperture an interiomarginal, extraumbilical-umbilical arch commonly bordered above by a narrow 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 Protista 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 from 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.

Related genera

Genera possibly related closely to Hedbergella are Asterohedbergella, Costellagerina, and Whiteinella, which are included with Hedbergella in the Hedbergellinae, but which have shorter ranges.

Asterohedbergella, which has a stellate outline, is from the Upper Cretaceous (M. to U. Cenomanian) of Israel. Costellagerina, which has a lobate outline, is from the Upper Cretaceous (Cenomanian to Campanian) and is cosmopolitan. Whiteinella, which has a pustulate surface, is from the U. Cretaceous (M. Cenomanian to M. Turonian), is also cosmopolitan.

References

• Cretaceous planktonic foraminifera: Part 1 -Cenomanian. A.R Loeblich Jr and Helen Tappan 1961. Micropaleontology, Vol 7 no 3 July 1961
• Hedberbellidae in Forminiferal Genera and their Classification Loeblich and Tappan, 1988.

Further reading

Reolid, M.; Sanchez-Quinonez, C.A.; Molina, E.; Alegret, L. (1 January 2015). "Palaeoenvironmental turnover across the Cenomanian-Turonian transition in Oued Bahloul, Tunisia: foraminifera and geochemical proxies". Palaeogeography Palaeoclimatology Palaeoecology. 417: 491–510. doi:10.1016/j.palaeo.2014.10.011. Retrieved 13 April 2015.