Megalospheric Forms Research Articles

Comments on “Morphogenesis of Balkhania balkhanica Mamontova, 1966 (benthic foraminifera) from Lower Cretaceous successions along the northern Tethyan margin (NE and Central Iran)”

The study by Gheiasvand and Bartolini (2023) treated Balkhania balkhanica and Torinosuella peneropliformis as morphotypes of a single species, Balkhania balkhanica, leading to incorrect conclusions about its characteristics. Their analysis overlooked key aspects of the life cycle, morphotypes, ecological roles, and paleogeographical distribution of B. balkhanica due to a misunderstanding of foraminiferal systematics. Notably, its megalospheric forms can reach a maximal diameter of 5.2 mm, whereas its microspheric forms may reach up to 15 mm. Its stratigraphic range is limited to the Barremian-early Aptian interval. Although B. balkhanica and Choffatella decipiens share equivalent ecological niches, they are not found together in the same strata. Ch. decipiens has a much wider distribution, over most of the Tethys realm, whereas Balkhania balkhanica is primarily found in the northern Tethys platforms, with the notable exception of Lebanon in the southern Tethys platforms.

Characters ofNummulites multiplicutiospiralisn. sp. from the Qarara Formation, Maghagha, Nile Valley, Egypt

AbstractNummulites multiplicutiospiralisn. sp. is described and illustrated for both generations from a claystone of Lutetian age in the Middle Eocene Qarara Formation, Maghagha, Nile valley, Egypt. Previously considered to beNummulites gizehensis, we describe this form as a new species based on diameter of the test and protoconch sizes, septal shape and granulations. The primary feature of this species is spiral multiplication, seen in spiral section. The species is also characterized morphologically by lenticular to flat tests with rounded periphery, wrinkled to broadly meandering septal filaments and few granules on the periphery in microspheric forms. The granules are spirally arranged on the septal filaments in megalospheric forms. Chambers are longer than high and the spire is irregular. The new taxon belongs to theNummulites partschiGroup, SubgroupN. gizehensis. Reflexive coiling in the spiral may develop through ontogeny as inN. rollandi, the species which was considered to be an index species in the southern Tethys (Boukhary et al., 1982 and Boukhary et al. 2010). The characters of the new species, as well as its retrogenesis and reflexive coiling, should be further studied in general inNummulitesspp., to understand the importance of such characters phylogenetically.

BENTHIC FORAMINIFERA AS POLLUTION INDICES IN THE MARINE ENVIRONMENT OF WEST COAST OF INDIA

Two ecosystems affected by acidic pollutants (Thana Creek, Bombay and inshore area of Trivandrum, Kerala) and two other ecosystems affected by alkaline pollutants (Cola Bay, Goa and inshore area of Karwar, Karnataka) were studied for pollution effects monitoring through Foraminifera. In the Thana Creek area, Bombay, the magnitude of corrosive effect, lower—than—normal ornamentation, deepening of grooves and sutural thickenings, enlargement of pores, widening of apertures in Foraminifera were taken as indices of pollution effect. In the, Cola bay area, Goa, the environment becomes hypertrophic resulting in large—sized, robust, mostly megalospheric forms of Ammonia. Elphidium and Florilus scaphum are recorded at the proximal zone near the discharge point; miliolids in the transitional zone and dominantly smaller—sized Nonionella, Fursenkoina pontoni, Bulimina marginata at the distal zone quite far from thc discharge point where pollutants are diluted and dissipated. In the Karwär area, Karnataka, pollutant causes reduced diversity with a decrease in foraminiferal population. Moreover, there is a reduction in size followed by test wall thinning in Nonion and Ammonia, increase of agglutinated forms near shore, and dispersal and dilution of the pollutants resulting in foraminiferal abundance. In the Trivandrum area, Kerala, the effluent effect presents morphological anomalies (Operculina, Cibicides), erosion along peripheries, induced growth in last few chambers, inferred dissolution and consequent destruction of small, thin—walled forms suggested by their absence, thus leaving only the larger ones in the entire area. Living/dead ratio is negatively oriented at all sites.

A revised suprageneric classification of American orthophragminids with emphasis on late Paleocene representatives from Jamaica and Alabama

Paleocene orthophragminids from the American bioprovince were studied from the Nonsuch Formation in Jamaica and the Salt Mountain Limestone in Alabama, the latter being the type locality of Discocyclina blanpiedi (Vaughan) and Discocyclina cookei (Vaughan). Species traditionally assigned to Athecocyclina Vaughan, Neodiscocyclina Caudri and Hexagonocyclina Caudri are redescribed and a new systematic classification of American orthophragminids is proposed based on the newly discovered microspheric forms of Paleocene species of Hexagonocyclina and Neodiscocyclina and Eocene Stenocyclina Caudri. Hexagonocyclina, questionably placed in Orbitoclypeidae Brönnimann in previous works, possesses an orbitoclypeid-type microspheric juvenarium justifying its placement in this family, whereas Stenocyclina and Pseudophragmina are transferred to Discocyclinidae Galloway after identifying the discocyclinid-type microspheric juvenarium. The genus Proporocyclina Vaughan & Cole is considered invalid and is assigned to Pseudophragmina. The genus Neodiscocyclina Caudri, possessing an orbitoclypeid-type juvenarium, is interpreted as a junior synonym of Orbitoclypeus Silvestri, a genus widely occurring in the Tethys. Athecocyclina has a typical discocyclinid-type microspheric juvenarium and is characterized by the development of immature radial subdivisions in the annular chambers, which never form complete septula. An evolutionary lineage for Orbitoclypeus weaveri consisting of O. weaveri blanpiedi and O. weaveri weaver is established for the first time herein. The Hexagonocyclina cristensis lineage, consisting of H. cristensis cristensis and H. cristensis meandrica, and the Athecocyclina stephensoni lineage, consisting of A. stephensoni macglameriae and A. stephensoni stephensoni, are provisionally suggested based on the morphometry and early chamber arrangement of megalospheric forms. The superposition of the two subspecies in the Orbitoclypeus weaveri lineage is shown from the Salt Mountain Limestone.http://zoobank.org/urn:lsid:zoobank.org:pub:493F043E-22D3-49CD-A427-D5159F249BD2

Strategies in times of crisis-insights into the benthic foraminiferal record of the Palaeocene-Eocene Thermal Maximum.

Climate change is predicted to alter temperature, carbonate chemistry and oxygen availability in the oceans, which will affect individuals, populations and ecosystems. We use the fossil record of benthic foraminifers to assess developmental impacts in response to environmental changes during the Palaeocene–Eocene Thermal Maximum (PETM). Using an unprecedented number of µ-computed tomography scans, we determine the size of the proloculus (first chamber), the number of chambers and the final size of two benthic foraminiferal species which survived the extinction at sites 690 (Atlantic sector, Southern Ocean, palaeodepth 1900 m), 1210 (central equatorial Pacific, palaeodepth 2100 m) and 1135 (Indian Ocean sector, Southern Ocean, palaeodepth 600–1000 m). The population at the shallowest site, 1135, does not show a clear response to the PETM, whereas those at the other sites record reductions in diameter or proloculus size. Temperature was similar at all sites, thus it is not likely to be the reason for differences between sites. At site 1210, small size coincided with higher chamber numbers during the peak event, and may have been caused by a combination of low carbonate ion concentrations and low food supply. Dwarfing at site 690 occurred at lower chamber numbers, and may have been caused by decreasing carbonate saturation at sufficient food levels to reproduce. Proloculus size varied strongly between sites and through time, suggesting a large influence of environment on both microspheric and megalospheric forms without clear bimodality. The effect of the environmental changes during the PETM was more pronounced at deeper sites, possibly implicating carbonate saturation.This article is part of a discussion meeting issue ‘Hyperthermals: rapid and extreme global warming in our geological past’.

Biometric Analysis of Nummulites PachoiSaid, 1951 (topotype, Late Lutetian) from El Arag Oasis, Egypt

AbstractNummulites pachoi Said, 1951 is described and illustrated for the first time from topotypic material from the Late Lutetian Mokattam Formation of El Arag Oasis, Egypt, including the first photographs of both microspheric and megalospheric generations. Nummulites pachoi spans the SBZ 16 of Late Lutetian age. This species is phylogenetically parallel to N. praelyelliBoukhary & Kamal, 2003. Although, N. pachoi and N. praelyelli exhibit the same ontogenetic trend, from tight to lax, the development of granulation in the megalospheric form of N. pachoi is a progressive character through time, unlike that in N. praelyelli. Nummulites pachoi is larger, flatter and with an opposite ontogenetic trend compared with Nummulites gizehensis, although both have similar protoconch diameters. The author who first recognized the name “pachoi” as a species-level designation should be given credit for naming the species. Because Said (1951) raised the rank of de la Harpe's race pachoi to specific level, according to the rules of zoological nomenclature, Said should be recognized as the author of the species.

Bartonian reticulate Nummulites of Kutch

Nummulites with reticulate septal filaments stratigraphically span from the Bartonian to the Rupelian Stages. The size of the proloculus of the megalospheric forms of reticulate species helped recognise N. fabianii – N. fichteli lineage in western Tethys. Unlike the species of this lineage, N. ptukhiani, described from Armenia, is characterised by an unusually large proloculus. A possibly second lineage of reticulate species comprising N. ptukhiani is recently reported from Lutetian – Bartonian succession of Tanzania. The present study examines reticulate species from palaeogeographically adjacent Bartonian succession of Kutch. The statistical analysis of the biometric data suggests the presence of three distinct species, referred to Nummulites ptukhiani, N. aff. hormoensis and N. acutus. The reticulation starts developing in N. acutus that ranges from P13 to P14 in its type locality, Kutch. We infer that Nummulites ptukhiani and N. aff. hormoensis possibly evolved from N. acutus in Zone P14. A binary tree model based on Classification and Regression Tree is proposed to statistically discriminate the three reticulate species.

Paleocene-earliest Eocene Larger Benthic Foraminifera and Ranikothalia-bearing carbonate paleo-environments of Costa Rica (South Central America)

Here we present a biostratigraphic and systematic revision of American Ranikothalia, based on outcrop collections form Costa Rica end westernmost Panama and on type collections of the Naturhistorisches Museum Basel. Paleocene-lowermost Eocene Ranikothalia-bearing shallow-water limestones occur in three distinct palaeogeographic settings along the Southern Central American convergent margin: 1. The Barra Honda Limestone (Tempisque Basin, Costa Rica) is, according to 87Sr/86Sr-ratios and biostratigraphy of mid Selandian to late Thanetian (? earliest Ypresian) age. Tectonic uplift and temporary demise of a Middle American Arc segment during the Selandian allowed the formation of the pure carbonates of the Barra Honda Limestone. The upper well-bedded subunit exposes a higher energy facies, in which Neodiscocyclina spp. and Ranikothalia catenula group (redefined here) are locally abundant. Open marine facies with Morozovella velascoensis interfinger in a small scaled facies pattern in the topmost part. Tectonic subsidence and resumed arc activity resulted in rapid eutrophication/drowning. 2. Herradura – Quepos carbonate shoals on oceanic seamounts. The Herradura and Quepos terranes may represent the earliest seamounts formed by the Galapagos hotspot plume tail activity, >1000km to the SW of their present-day position. Pillowed lava flows and subaerial volcanic breccias occur with Upper Palaeocene-lowermost Eocene shallow-water limestones rich in Ranikothalia gr. catenula, Neodiscocyclina spp. and coralline algae. 3. Burica Peninsula – carbonate shoal on an accreted oceanic plateau. An Upper Paleocene carbonate shoal established on part of the Inner Osa Igneous Complex after its accretion to the western edge of the CLIP (Caribbean Large Igneous Province) and its possible emersion. In situ rhodoid limestones of the Río Palo Blanco (W-Panama) contrast with redeposited material in turbidites and debris flow breccias, interbedded with siliceous pelagic limestones and arc-derived mudstones. A morphometric study on 150 axial sections of Ranikothalia spp. from all studied settings reveals a morphologic continuum between megalospheric (A) forms and microspheric (B) forms previously described as several species, here grouped as the R. gr. catenula. We conceive that these co-occurring morphotypes belong to one biological species. The separation of this group into 2 or 3 genera seems highly artificial, since many samples contain transitional forms between the “sub-evolute” microsphreric forms “Caudrina†soldadensis (R. catenula soldadensis herein) and the involute “Chordoperculinoides†bermudezi (R. c. bermudezi herein). Neither from previous studies nor from our material we can conclude on a biostratigraphic relevance of the various morphotypes. In particular, we cannot confirm a stratigraphic succession from flatter (R. c. soldadensis) to more robust (R. c. bermudezi) forms. Shape and shell thickness distribution of morphotypes of the Ranikothalia gr. catenula can be interpreted in terms of hydrodynamic energy and light availability in their habitat, in comparison with observations made on living LBF. This interpretation matches the hydrodynamic energy deduced from the microfacies and the abundance of photosynthetic red algae in our thin sections. Flat lenticular delicate A-forms (R. c. catenula) occur together with delicate B-forms (R. c. soldadensis) both in shallow protected and deeper off-shore calm water areas. The most robust B-form R.c. bermudezi may be a good indicator of shallow, high energy palaeo-environments. Possible Paleoceme dispersal routes for Amerucan Ranikothalia are discussed.

Morphologic Variation and Microspheric Forms ofParafusulina japonicafrom Tamanouchi, Itsukaichi-Ome Area, West Tokyo, Japan

Specimens of Parafusulina japonica (Gumbel), middle Permian (late Wordian) Fusulinoidea from a small, exotic limestone block within the Middle Jurassic Kamiyozawa Formation exposed at Tamanouchi, west Tokyo, Japan, show considerable morphologic variation and include microspheric forms. The megalospheric specimens vary greatly in the shape and size of their tests, expansion of their tests, and in the shape and size of their proloculi. Two microspheric specimens are about twice the size of the megalospheric specimens and show early whorls to be schubertellid-like. The presence or absence of an initial one or two endothyroid whorl is not established. The shape of septal folds seems distinctive as they have slightly wider, flattened or slightly rounded dome-shaped tops both in megalospheric and microspheric forms. Cuniculi are absent in early whorls and quite poorly developed in later whorls where they are low inconspicuous features, suggesting a relatively early evolutionary stage in the Parafusulina lineage. The features of the megalospheric specimens have led some authors to place this species in the genus Parafusulina (Skinnerella) or even as a separate genus, Skinnerella. However, the microspheric specimens are much more typical of the genus Parafusulina (Parafusulina), and so P. japonica will be placed in the unsubdivided genus Parafusulina.

Environmental significance of morphological variations in the foraminifer Ammonia aomoriensis (Asano, 1951) and its molecular identification: A study from the Yellow Sea and East China Sea, PR China

Ammonia aomoriensis (Asano 1951) was isolated from 78 samples collected from the Yellow Sea and East China Sea during 2010 to 2014. The species exhibits dimorphism (microspheric and megalospheric forms) and different coiling directions (dextral and sinistral). A fragment of SSU rDNA was sequenced for four specimens of A. aomoriensis exhibiting different morphologies (dextral vs. sinistral, microspheric vs. megalospheric). Our results show that A. aomoriensis from our study sites branch within previously obtained sequences of the same species. In order to test whether morphological differences are environmentally controlled we investigated 667 specimens from Qingdao and Jiaozhou Bay among which 290 were right coiled (dextral) and 377 were left coiled (sinistral). Similarly, 525 were microspheric and 142 were megalospheric. A correlation coefficient was computed to evaluate the relationship between foraminiferal morphology (dimorphism and coiling direction) and environmental parameters (temperature and salinity). A significant positive correlation was detected between the ratio of microspheric/megalospheric forms and salinity (r=0.719, p<0.001). No correlation was detected between morphological variations and temperature. Our findings suggest that the ratio of microspheric/megalospheric forms in A. aomoriensis can be used to infer past salinity conditions (and thus fresh water influx) in study areas off China.

TAXONOMIC AND BIOSTRATIGRAPHIC REASSESSMENT OFLITUOSEPTA RECOARENSISCATI, 1959 (FORAMINIFERA, LITUOLACEA)

The large lituolid foraminifer, Lituosepta recoarensis Cati, 1959, is recorded from Lower Jurassic shallow-water carbonate deposits of the Southern Tethyan area. This species is usually not abundant and its taxonomic status, as well as its stratigraphic distribution, have not always been well defined. The analysis of Cati’s stratigraphic section (Monti Lessini area, Monte Scandolara, north-eastern Italy, Southern Alps), from which the type material originates, yielded numerous well-preserved topotypes and permitted a detailed structural and morphological assessment of Lituosepta recoarensis . Microspheric and megalospheric generations are herein described and illustrated. Two generations of megalospheric forms, A1 and A2, are distinguished on the basis of morphological features. Comparing the Lituosepta species, the genus Planisepta (type species Lituosepta compressa Hottinger) is considered invalid and the original nomenclature Lituosepta compressa is retained. In the southern Tethyan margin the stratigraphic occurrence of L. recoarensis spans the upper Sinemurian–Toarcian interval.

Biometric Analysis of Lepidocyclina (Nephrolepidina) from Baba Formation (Late Oligocene) in Bai-Hassan Well-25, Kirkuk Area, Northeast Iraq

The investigation is based on a subsurface sequences of bioclastic limestone in Kirkuk area, Northeastern Iraq. These sequences were deposited in a shallow open marine environment during Late Oligocene. Tests of larger foraminifera Lepidocyclina(Nephrolepidina) are abundant in the lower and upper parts of the Baba Formation. Biometric investigations of the Megalospheric forms of Nephrolepidina assemblages from, Bai-Hassan well- 25 section led to recognize three morphometrically defined species by the combination of three parameters, 1- the degree of embracement of the protoconch by the deuteroconch (Factor A), 2- the numbers of accessory auxiliary chambers on the deuteroconch (Factor B), and 3- (Factor C ) which expressed by the protoconch angle( ) formed by the two hypothetical line from the center of protoconch throught the outer attachment points of the deuteroconch walls with protoconch.

985 Density and relative abundance of microspheric and megalospheric forms of Nummulites as sedimentologic and taphonomic indicators

985 Density and relative abundance of microspheric and megalospheric forms of Nummulites as sedimentologic and taphonomic indicators

Striate Nummulites (:Foraminiferida) from the Early Oligocene rocks of Southwestern Kutch

Megalospheric form of a striate Nummulites, provisionally identified here as Nummulites sp. aff. chavannesi de la Harpe, is documented from the Early Oligocene rocks of SW Kutch, Gujarat. This striate Nummulites occurs in association with N. fichteli-clipeus Group, N. cf. fichteli, Heterostegina, Operculina and Gypsina. High abundance of microspheric tests of reticulate Nummulites and virtual absence of microspheric tests of striate Nummulites reflect contrasting success of growth and sexual reproduction of the two groups of sympatric Nummulites.

Precursors of the Nummulites gizehensis and N. partschi group from Egypt

Studies on the precursors of Nummulites gizehensis group and Nummulites partschi group from the Eocene of Egypt has permitted the identification of seven species. Two of these, namely Nummulites rushdisaidi n.sp. and Nummulites qenaensis n.sp. are new. This study suggests that the group might have evolved polyphyletically since the early Ypresian with more marked diversification during the Middle Eocene and attained maximum test size during Bartonian ( Nummulites lyelli Archiac and Haime, 1853). This group has been studied in stratigraphic sequence, taking into consideration their geographic distribution. Some known Ypresian precursors such as Nummulites delaharpei Said, 1951 and Nummulites mariettei Said, 1951 (topotypes) and Nummulites rollandi Ficheur, 1890 are also described and illustrated for the first time. During the evolution, retrogenesis was noticed with species evolving from lax to tightly coiled whorls in microspheric forms, whilst the megalospheric forms become progressively lax internally and tighter externally, or vice versa. In addition, duplication of the spiral was noticed in N. qenaensis n.sp. Also, reflexive coiling expressing change in the course of the septa in the outer whorls has been noticed during the ontogeny in N. rollandi Ficheur, 1890.

The Late Eocene Evolution of Nummulitid ForaminiferSpiroclypeusin the Western Tethys

Megalospheric forms of Priabonian Spiroclypeus of the Western Tethys were morphometrically investigated. Based on the reduction of the average number of undivided, post-embryonic chambers, the investigated populations are grouped into two successive, phylogenetically linked species, S. sirottii sp. nov. and S. carpaticus. The evolution is also demonstrated by the increase of the number of secondary chamberlets in particular chambers, by the increase of the diameter of the first two whorls and by that of the size of the proloculus, although the latter turned out to be also ecologically controlled. This evolution is supported by the stratigraphic succession of populations in the Mossano section (N Italy) and by the change of accompanying fossils. Lacking in upper Bartonian beds, the first appearance of genus Spiroclypeus seems to be synchronous with the beginning of the late Eocene. The newly described S. sirottii is associated with Heterostegina reticulata mossanensis and orthophragmines containing forms o...

The Middle to Late Eocene Evolution of Nummulitid ForaminiferHeterosteginain the Western Tethys

Megalospheric forms of Western Tethyan late Bartonian to late Priabonian involute Heterostegina from numerous localities, marking different ecological conditions, were morphometrically investigated. They belong to three species, H. armenica, H. reticulata, and H. gracilis based on the presence/absence of granulation, on the chamberlet characteristics and on the relative size of proloculus. Within these species a very rapid evolution could be observed in the reduction of the number of operculinid chambers, in the increase of the number of chamberlets and partially in the increase of the proloculus size. This evolution is demonstrated by stratigraphic superpositions in several localities (especially in the Mossano section), and is supported also by the change of co-occurring fossils, starting with the disappearance of large-sized Nummulites, then followed by the appearance of the genus Spiroclypeus and then by the disappearance of orthophragmines of middle Eocene acme. Based on the reduction of operculinid ...

El género Heterostegina (Nummulitidae, Foraminifera) en el Mioceno superior del SO de España

Resumen Se realiza el estudio sistematico de los ejemplares pertenecientes al genero Heterostegina de diversos niveles lumaquelicos en sedimentos de la unidad arenosa basal de la serie neogena en el sector occidental de la Cuenca del Guadalquivir (SO de Espana). La determinacion especifica de estos ejemplares ha llevado a una revision y correccion de la especie Heterostegina gomez-angulensis Perconig . Se describe y figura por vez primera la generacion microesferica de esta especie, se realiza una redescripcion de las formas megaloesfericas que permite la distincion de dos morfotipos diferenciados, y se evalua su interes cronoestratigrafico.

Duquepsammiidae, a New Family, and Duquepsammia, a New Genus of Agglutinated Foraminifers

Duquepsammiidae, n. fam., includes only one genus, Duquepsammia, n. gen., of which Spiroplectoides cubensis is the type species. Duquepsammia is characterized by an inner structure in the biserial chambers and in the microspheric form by a relatively large number of chambers and whorls in the spiral stage. The megalospheric form is a homeomorph of Spiro- plectammina Cushman.

Dimorphic forms of recent foraminifera: An additional tool in paleoclimatic studies

Limited culture studies of foraminiferal species show that the ratios of dimorphic forms are not constant and are affected by extremes of temperature. This feature might be utilized for paleoclimatic studies. To test this possibility ratios of microspheric/ megalospheric forms were obtained for Bolivina skagerrakensis Qvale and Nigam, at different levels in a core (15530-4) from the Skagerrak, eastern North Sea. The values show considerable fluctuations and can be correlated with two other paleotemperature scales: the total number of benthic foraminifera and the oxygen isotope ratio. It is concluded that the microspheric/megalospheric ratios of foraminifera can be used as index of paleoclimate and that the higher ratios indicate relatively warm climates. However, this inference needs to be confirmed by additional culture studies under controlled temperature conditions, and faunal studies of cores where paleotemperatures are already established with the help of oxygen isotopes.