Hedbergella infracretacea Glaessner 1937 from: Leckie, M.R. (1990): Middle Cretaceous Planktonic Foraminifers of the Antarctic Margin: Hole 693A, ODP Leg 113. In: Proceedings of the Ocean Drilling Programme Vol. 113 Eds: Parker, P.F..Kennett, J.P.O'Connell, S..Pisias, N.G. p. 319-324 | . |
Notice: This catalogue page may contain unedited data.
|
Species Hedbergella infracretacea Glaessner 1937 |
|
|
|
| Alternative name: |
|
| Diagnosis / Definition: |
Leckie (1990):
Test small, maximum diameter to 0.31 mm. Five to six
subspherical to ovoid chambers in the final whorl, increasing gradually in size as added. The dorsal side varies from a low trochospire to flat;
low trochospire tends to be more prevalent in juveniles and five-chambered adults, although the populations display a continuous range of variation. Test surface perforate and slightly pustulose. Pores occur at the apices of the pustules. Pustules on earlier chambers of final whorl
occur in aggregates yielding subtle patterns suggestive of rugae. Aperture extraumbilical-umbilical; developed as a moderate arch with a thin imperforate rim |
| Discussion / Comments: |
Leckie (1990):
The subtle "rugosity" developed in this taxon differs
distinctly from the pattern in Hedbergella libyca or species of Rugoglobiqerina; the rugae of these latter taxa are non-perforate, the pores occur between rugae rather than being developed upon the ornament. This particular surface texture has been observed on several hedbergellids of
late Aptian to early Albian age (e.g., H. trocoidea and H. delrioensis of Krasheninnikov and Basov, 1983; H. delrioensis of Longoria, 1974; Hedbergella sp. 1, H. aff. trocoidea, H. gorbachikae and H. cf. rischi of Leckie, 1984; Blefuscuiana cf. aptica of Banner and Desai, 1988). It
is possible that the "rugosity" is a preservational artifact of hedbergellids of this age, although Leckie (in press) has argued against widespread poor preservation as the principal cause for the marked decline in planktonic foraminiferal diversity during latest Aptian-early Albian time. Another possibility is that it represents primary ultrastructure and
therefore is of Phylogenetic significance.
Hedbergella infracretacea (Glaessner) has been a problematic taxon, especially with regard to its relationship with H. delrioensis (Carsey) (see discussions by Hermes, 1969; Longoria, 1974; Masters, 1977; Price, 1977). Glaessner (1966) attempted to clarify the species concept of H.
infracretacea by illustrating three topotypes, all of which clearly show the absence of an apertural lip. This observation is ultimately what led the present author to assign the Hole 693A specimens to the H. infracretacea
group. Glaessner (1937) also notes that this taxon has five to six chambers in its final whorl. Other diagnostic characteristics emphasized by other authors include the small size of H. infracretacea and its variable
dorsal convexity. H. delrioensis s.s. is characterized by having four and one-half to five and one-half chambers in its final whorl, a flat dorsal side, a hispid test, and in possessing a spatulate lip. The populations from Hole 693A show a continuous range of variability in terms of size
(up to 0.31 mm), dorsal convexity (moderately elevated to depressed early coil), and number of chambers in the final whorl (5-6). However, no specimens were observed with a "hispid" test or with an apertural lip, and therefore classification within H. delrioensis was rejected. H.
infracretacea and H. delrioensis probably co-occur in some sediments of late Aptian to middle Albian age, but H. delrioensis s.s. is best developed in late Albian and Cenomanian assemblages (e.g., Price, 1977;
Leckie, 1984).
Hedbergella infracretacea differs from H planispira (Tappan) in lacking a well developed apertural lip and in lacking the characteristic circular outline of that taxon. In addition, H. planispira has up to eight chambers in the final whorl. Specimens of H. infracretacea from Hole 693A may include forms referable to H. rischi Moullade (H. aff. infracretacea
of Moullade, 1966).
Pflaumann & Krasheninnikov (1977):
H. infracretacea contains five to five and one-half ovoidal
chambers in the last whorl which increases very slightly, umbilicus
deep and narrow. In Hole 369A samples five-chambered specimens
are dominant in the late Aptian section, while in the Albian five and
one-half chambers are more common. Differences against H.
planispira: higher trochospiral, and narrow umbilicus, against H.
trocoidea: lower trochospiral and lower chamber number, smoother
surface, against H. delrionensis: last chamber shows no protrusion
towards the umbilicus, ovoid in shape with longest axis in direction of
growth. |
| Synonym list: |
Leckie (1990):
Pflaumann & Krasheninnikov (1977):
|
| Was used in synonym list of: |
|
|
| References: |
Glaessner,M.F. (1937):
Planktonische Foraminiferen aus der Kreide und dem Eozän und ihre stratigraphische Bedeutung.
In: Studies in Micropaleontology Vol. 1(1) p. 27-46
Glaessner,M.F. (1966):
Notes on foraminifera of the genus Hedbergella . Ecoglae geologicae Helvetiae Vol. 59 p. 179-185
Pflaumann,U. and Krasheninnikov,V.. (1977):
Early Cretaceous planktonic foraminifers from eastern North Atlantic, DSDP Leg 41 .
In: Initial Reports of the Deep Sea Drilling Project 41 , Abidjan, Ivory Coast, to Malaga, Spain, February-April 1975 Eds: Gardner, J..Herring, J.. p. 539-564
Leckie,M.R. (1984):
Mid-Cretaceous planktonic foraminiferal biostratigraphy off Morocco, Deep Sea Drilling Project Leg 79, Sites 545 and 547 . Initial Reports of the Deep Sea Drilling Project Vol. 79 p. 579–620
Leckie,M.R. (1990):
Middle Cretaceous Planktonic Foraminifers of the Antarctic Margin: Hole 693A, ODP Leg 113.
In: Proceedings of the Ocean Drilling Programme Vol. 113 Eds: Parker, P.F..Kennett, J.P.O'Connell, S..Pisias, N.G. p. 319-324
|
This work is licensed under a Creative Commons Attribution 2.5 License.
|
|
Taxon Concept provided by