Cassigerinella eocaenica


Classification: pf_cenozoic -> microperforate -> Cassigerinellidae -> Cassigerinella -> Cassigerinella eocaenica
Sister taxa: C. chipolensis, C. eocaenica, C. sp.,

Taxonomy

Citation: Cassigerinella eocaenica Cordey 1968
Rank: Species
Basionym: Cassigerinella eocaenica
Synonyms:
Taxonomic discussion: Although a number of authors (e.g., Blow, 1979; Li, 1986) considered C. eocaena Cordey as a junior synonym of C. winniana (Howe), SEM images of the holotype of C. winniana (Pl.16.4, Figs. 13-15) reveal that the test is lenticular in edge outline, one side of the test shows a concentration of several large, blunt pustules in the umbilical region, and the aperture is a narrow, extraumbilical arched slit at the base of the final chamber, and is surrounded by a narrow lip. These features, and the biserially enrolled planispiral coiling mode (see Li, 1986 for explanation), suggest that winniana should be reassigned to the benthic foraminifer genus Cassidulina. Well preserved, previously unillustrated specimens that were identified by Liu and others (1997) as C. winniana from Zone E18 in the Atlantic City (New Jersey) borehole samples (Liu, pers. comm., 1999) show strong similarity to the C. winniana holotype except for the presence of large, blunt pustules on both sides, rather than one side of the test (Pl.16.4, Figs. 16, 17). These specimens are now considered as Cassidulina winniana.
Rather than having a simple planispire with uniserial chamber coiling in the initial whorl, as suggested by Cordey’s (1968) original type illustrations and species description, Li’s (1986, fig. 6c) reillustration of the C. eocaenica holotype revealed that its early growth stage is characterized by compactly arranged biserial chambers that coil along a planispire or low trochospire. This coiling mode was more clearly demonstrated by Li and McGowran’s (1996 pl. 1, figs. 1-7) SEM images of specimens where they illustrated specimens designated as C. winniana (here considered as C. eocaenica) from lower Oligocene borehole samples in southern Australia. Two of these specimens are here re-illustrated (Pl.16.4, Figs. 20, 21). A specimen considered by Li and McGowran (1996, pl. 1, fig. 8) as transitional between C. eocaenica and C. chipolensis is also re-illustrated (Pl.16.4, Fig. 22). [Huber et al. 2006]

Catalog entries: Cassigerinella eocaenica;

Type images:

Short diagnosis: Differs from C. chipolensis and C. boudecensis by its smaller size, more compressed test, less inflation of the chambers, slower chamber size increase, and lower and broader aperture.

NB The short diagnoses are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus. They have initially been copied from the diagnostic characters/distinguishing features sections of the Eocene and Paleocene Atlases, they will be edited as the site is developed.

Description


Diagnostic characters: Differs from C. chipolensis and C. boudecensis by its smaller size, more compressed test, less inflation of the chambers, slower chamber size increase, and lower and broader aperture. [Huber et al. 2006]

Wall type: Finely perforate, monolamellar, surface smooth or may have minute pore mounds. [Huber et al. 2006]

Test morphology: Test very small, outline subcircular to broadly elliptical; periphery lobate, initially subacute, later becoming subrounded; chambers in early growth stage are compactly arranged in a biserial planispire or low biserial trochospire, later biserially enrolled with the chamber arrangement alternating in the coiling plane, moderately inflated, 8-9 visible in external view, increasing gradually and uniformly in size; sutures distinct, depressed, curved; aperture a lateromarginal, extra-umbilical arch. [Huber et al. 2006]

Size: Paratype diameter 0.11 mm, breadth 0.06 mm; maximum diameter 0.10-0.12 mm. [Huber et al. 2006]

Character matrix

test outline:Ellipticalchamber arrangement:Biserialedge view:Inequally biconvexaperture:Extraumbilical
umb chamber shape:Inflatedcoiling axis:N/Aperiphery:N/Aaperture border:N/A
sp chbr shape:Inflatedumbilicus:periph margin shape:Broadly roundedaccessory apertures:None
umbilical or test sutures:Moderately depressedumb depth:wall texture:Smoothshell porosity:Finely Perforate: 1-2.5µm
spiral sutures:Moderately depresseddiameter mm:0.11width mm:breadth mm:0.06
final-whorl chambers:5.0-6.0

Biogeography and Palaeobiology


Geographic distribution: Originally described by Cordey (1968) from an uppermost Eocene core drilled on Blake Plateau. Also recorded from lower Oligocene subsurface, outcrop samples of terrigenous clastic sediments in southern Australia (Li and McGowran, 1996) and pelagic carbonate sediments at Little Bahama Bank in the North Atlantic Ocean (Leckie and others, 1993). [Huber et al. 2006]

Isotope paleobiology: No data available. [Huber et al. 2006]

Phylogenetic relations: Uncertain. Li and McGowran (1996) postulated that C. eocaenica (= their C. winniana) was derived from Pseudohastigerina micra, but we consider this unlikely because of the smaller pore size, monolamellar rather than bilamellar wall, and planispiral to biserially enrolled coiling mode in C. eocaenica. The microperforate wall and occasional presence of pore mounds suggest a possible phylogenetic link with the Guembelitriidae, but no guembelitriid species have been recorded near the first occurrence of C. eocaenica (Fig. 16.1). Alternatively, the restricted occurrence of C. eocaenica to neritic environments and its unusual shell morphology suggest that the ancestor of this taxon may have been a benthic species. [Huber et al. 2006]

Biostratigraphic distribution

Geological Range:
Notes: Upper Eocene Zone E13 to middle Oligocene Zone O4 according to Li (1986). Blow (1979) illustrated metatypes (his pl. 51, figs. 7, 8) that were sent to him by W .G. Cordey from an upper Eocene (~Zone P16) core drilled on Blake Plateau, western North Atlantic. Li and McGowran (1996) recorded C. winniana ( =C. eocaenica) in southern Australia from lower Oligocene Zone NP23 and suggested, based on reports in the literature, that this species ranged down to the Zone P14/P15 boundary (= upper E13). McGowran and others (1992) reported the last occurrence of C. eocaenica near the P21a/P21b (=Zone O4/O5) boundary in the St. Vincent Basin of southern Australia. A specimen identified as Cassigerinella sp. by Leckie and others (1993, pl. 7, fig. 17), here considered synonymous with C. eocaenica, was reported in Zone P18 (=Zone O1) at ODP Site 628 on Little Bahama Bank. Pre-Oligocene reports of C. eocaenica require SEM verification of species identification because of the easy confusion of this species with Cassidulina winniana. [Huber et al. 2006]
Last occurrence (top): within O4 zone (28.09-29.18Ma, top in Rupelian stage). Data source: Eocene Atlas
First occurrence (base): within E13 zone (37.99-39.97Ma, base in Bartonian stage). Data source: Eocene Atlas

Plot of occurrence data:

Primary source for this page: Huber et al. 2006 - Atlas of Eocene Planktonic Foraminifera, chapter 16, p. 486

References:

Blow, W.H., (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea). E. J. Brill, Leiden, 1413 pp.

Cordey, W.G., (1968). A new Eocene Cassigerinella from Florida. Palaeontology, 11: 368-370.

Cordey, W.G., (1968). Morphology and phylogeny of Orbulinoides beckmannii (Saito 1962). Palaeontology, 11(3): 371-375.

Howe, H.V., (1939). Louisiana Cook Mountain Eocene foraminifera. Bulletin of the Geological Survey of Louisiana, 14: 1-122.

Huber, B.T.; Olsson, R.K. & Pearson, P.N., (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene microperforate planktonic foraminifera (Jenkinsina, Cassigerinelloita, Chiloguembelina, Streptochilus, Zeauvigerina, Tenuitella, and Cassigerinella) and Problematica (Dipsidripella). In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera, Cushman Foundation Special Publication 41. Cushman Foundation Special Publication. Allen Press, Lawrence, Kansas, pp. 461-508.

Leckie, R.M.; Farnham, C. & Schmidt, M.G., (1993). Oligocene planktonic foraminifer biostratigraphy of Hole 803D (Ontong Java Plateau) and Hole 628A (Little Bahama Bank), and comparison with the southern high latitudes. In: Berger, W.H., Kroenke, L.W. and al., e. (Editors), Proceedings of the Ocean Drilling Program, Scientific Results. Ocean Drilling Program, College Station, Texas, pp. 113-136.

Li, Q. & McGowran, B., (1996). The planktonic foraminifer Cassigerinella winniana (Howe) from southern Australia: Comments on its lineage recognition. Revista Española de Micropaleontología, 28: 97-103.

Li 1986 [sorry, not in our bibliography yet]


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Cassigerinella eocaenica compiled by the pforams@mikrotax project team viewed: 26-9-2017

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