Clavigerinella caucasica Subbotina 1958 from: Pearson, P.N.Olsson, R.K.Hemleben, C.Huber, B.T.Berggren, W.A. (2006): Atlas of Eocene Planktonic Foraminifera. p. 1-513 | . |
Notice: This catalogue page may contain unedited data.
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Species Clavigerinella caucasica Subbotina 1958 |
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| Diagnosis / Definition: |
Pearson et al. (2006):
DESCRIPTION.
Type of wall: Smooth normal perforate or weakly cancellate; characterized by pores with a wide range of diameters; possibly spinose.
Test morphology: Planispiral or pseudoplanispiral,
evolute, biumbilicate or showing a slightly raised spiral side and very shallow umbilicus; 4-4 1/2 rapidly enlarging chambers in the final whorl; early chambers rounded, final 1 -4 chambers radially elongate, digitate, peripheral outline strongly lobulate; distal
chamber ends on final chambers acute, distinctly pointed; equatorial high arched aperture, symmetrical or slightly asymmetrical, bordered by smooth broad imperforate lips; web-like relict apertural lips often
present along sutures; sutures shallow, straight,
becoming curved in later stages, short compared to
overall chamber length.
Size: Diameter 0.75 mm, thickness 0.20 mm
(Subbotina, 1958). |
| Discussion / Comments: |
Pearson et al. (2006):
DISTINGUISHING FEATURES.-
Clavigerinella
caucasica differs froin other species of Clavigerinella
by having adult chambers that taper into an acute or
pointed tip (Subbotina, 1958).
DISCUSSION.-
Clavigerinella caucasica has
commonly been regarded as a junior synonym of C.
eocanica (e.g., Blow, 1979; Pearson, 1993). However,
the occurrence of a number of specimens extremely
close to the holoype of C. caucasica, which we illustrate
in SEM for the first time (Pl. 8.2, Figs. 1-3), in the
uppermost lower Eocene of the Austrian Helvetikum
Section and Tanzania (Tanzanian Drilling Project Site
2; Pearson and others, 2004) indicates that it is a
distinctive, recurring morphotype with a restricted range.
Moreover, the pointed chambers appear to represent the
first stage in the gradual morphological transition to
Hantkenina (Coxall and others, 2003).
PHYLOGENETIC RELATIONSHIPS.-
This species
probably evolved from C. eocanica in the latest early Eocene by slight tapering of the adult chambers. Hantkenina singanoae n. sp., which bridges the gap between digitate and tubulospinose morphologies, evolved from C. caucasica by further tapering and constriction of the chambers to form a pronounced terminal nub or proto-tubulospine.
STRATIGRAPHIC RANGE.-
Subbotina's holotype is simply listed as being Eocene in age. Our observations in Austria and Tanzania suggest a very restricted range
in the uppermost part of early Eocene Zone E7.
GEOGRAPHIC DISTRIBUTION.-
Known only from the Caucasus Mountains, Austria and Tanzania.
STABLE ISOTOPE PALEOBTOLOGY. No data
available. |
| Systematics: |
35
Ordo Foraminiferida
Superfamilia Globigerinaceae
Familia Hantkeninidae
Genus Clavigerinella
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| Synonym list: |
Pearson et al. (2006):
1958 Hastigerinella caucasica Subbotina. - Subbotina : p.58 pl. 11; fig. 8a-b [middle Eocene,Belaya River,Northern Caucasus,
USSR]
2006 Clavigerinella caucasica Subbotina. - Pearson et al. : p.220 pl. 8.2; fig. 1-8 (Pl. 8.2, Figs. 1-3: new SEMs of the holotype of
Hastigerinella caucasica Subbotina)
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| Specimen: |
All-Union Petroleum Scientific Research Geological Prospecting Institute - Leningrad, Inventory number: VNIGRI 440-58
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| References: |
Subbotina,N.N. (1958):
New genera and species of foraminifera.
In: Trudy, VNIGRI, new series, 115. , Microfauna of the USSR Vol. 9 Eds: Bykova, e.N.K.. p. 5-106
Coxall,H.K..; Huber,B.T. and Pearson,P.N. (2003):
Origin and morphology of the Eocene planktonic foraminifer Hantkenina . Journal of Foraminiferal Research Vol. 33 p. 237-261
Pearson,P.N.; Olsson,R.K.; Hemleben,C.; Huber,B.T. and Berggren,W.A. (2006):
Atlas of Eocene Planktonic Foraminifera. p. 1-513
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