Oligocene larger foraminifera by Sampa Sarkar
Carbonate accretion in the larger foraminifera Nummulites Lamarck proceeds with the individual la... more Carbonate accretion in the larger foraminifera Nummulites Lamarck proceeds with the individual laminae being laid down on the sediment-free test surface at the time of chamber addition. In a marked departure from this general pattern, a few microspheric specimens of reticulate Nummulites collected from the Lower Oligocene rocks of southwestern Kutch, India were found to exhibit overgrowth of the test wall upon other benthonic foraminifera (OBF). It seems that wall overgrowth may have constrained the OBF specimens that plausibly thrived on the reticulate Nummulites.
A new morphotype of the megalospheric form of the larger foraminifer Nummulites cf. fichteli Mich... more A new morphotype of the megalospheric form of the larger foraminifer Nummulites cf. fichteli Michelotti from the Lower Oligocene of southwestern Kutch, western India is documented here for the first time. This morphotype shows ontogenetic change of orientation of the coiling plane and is apparently endemic. Previous studies on the megalospheric form of this species had led to the documentation of lenticular, conical and saddle-shaped morphotypes. These multiple morphotypes reveal different adaptations to varied bottom conditions.
Eocene larger foraminifera by Sampa Sarkar
SEM study of the dimorphic tests of Middle Eocene larger foraminifera Nummulites vredenburgi Prev... more SEM study of the dimorphic tests of Middle Eocene larger foraminifera Nummulites vredenburgi Prever collected from western Kutch has revealed the occurrence of hitherto unreported coarse passageways within the spiral laminae and the pillars. These passageways, superficially resembling the canals in the lateral wall of Ranikothalia Caudri, Miscellanea Pfender and Pellatispira Boussac, plausibly facilitated protoplasm movement in the lateral part of the examined Nummulites taxon.
A foraminiferal shell bed (informally referred to as the 'obtusus bed') occurring in the upper pa... more A foraminiferal shell bed (informally referred to as the 'obtusus bed') occurring in the upper part of the Harudi Formation (Middle Eocene) in Kutch has yielded evidences of diverse shell-gravel taxa (mostly macroinvertebrates). In this communication, we report new evidences of shell-gravel taxa in the form of clavet and tubular borings of endolithic fauna and epibenthic growth of solitary scleractinian coral and cyclostome bryozoa for the first time. The borings include Gastrochaenolites Leymerie, Trypanites Magdefrau and cf. Trypanites Magdefrau. The coral and the bryozoan are Trochocyathus sp. Edward and Haime and 'Proboscina' sp. Audouin respectively. This highly diverse shell-gravel fauna subsisted solely on the larger foraminifera of the 'obtusus bed'. So far, such an association is unknown from any other part of India.
Journal of the Geological Society of India, 05/2015; 85(5):586-590.
Publications: Eocene larger foraminifera by Sampa Sarkar
The Middle Eocene larger foraminifera Nummulites obtusus (Sowerby, 1840) Form B has tripartite sp... more The Middle Eocene larger foraminifera Nummulites obtusus (Sowerby, 1840) Form B has tripartite spire. Dearth of information concerning marginal cord and chamber in the terminal whorls of this taxon has, so far, constrained our understanding on the spire morphogenesis. Present SEM study has revealed septa and septal filaments in the lateral and median parts of the test respectively in sharp contrast to the Nummulites bauplan. Terminal whorls reveal a growth paradigm where chamber construction is not restricted to the median plane of the test.
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Oligocene larger foraminifera by Sampa Sarkar
Eocene larger foraminifera by Sampa Sarkar
Journal of the Geological Society of India, 05/2015; 85(5):586-590.
Publications: Eocene larger foraminifera by Sampa Sarkar
Journal of the Geological Society of India, 05/2015; 85(5):586-590.