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Species Parasubbotina eoclava Coxall et al. 2003


Diagnosis / Definition:
Pearson et al. (2006):
DESCRIPTION. Type of wall: Reticulate Clavigerinella-type wall texture, spinose in life. Test morphology: Very low trochospiral, somewhat laterally compressed, lobulate-petaloid in outline, chambers globular and well separated with a tendency for the final chamber to become slightly radially elongated; in spiral view surface flattened so that chambers of inner whorl are distinguishable; sutures straight, slightly depressed; in umbilical view 4 chambers in the final whorl, increasing rapidly in size, umbilicus moderately small, narrow and deep, sutures straight and slightly depressed; in edge view primary aperture a moderately high arch, interiomarginal, umbilicalextraumbilical, bordered by a well developed, asymmetrical flaring lip that extends from the umbilicus to the equatorial margin. Size: Holotype maximum diameter 0.48 mm, thickness 0.26 mm.
Discussion / Comments:
Pearson et al. (2006):
DISTINGISHING FEATURES. Parasubbotina eoclava is characterized by its low trochospiral coiling, Clavigerinella-type reticulate wall texture, an interiomarginal umbilical-extraumbilical aperture bordered by a broad, flaring apertural lip, and a tendency toward radial extension of the last one or two chambers which anticipates the clavate morphology of Clavigerinella (from which it gets its name). It differs from Parasubbotina inaequispira (Subbotina) in possession of a distinctive flaring lip, more compressed morphology and in the more rapid increase in chamber size through the final whorl. It differs from Clavigerinella eocanica in consistently showing low trochospiral rather than planispiral coiling, having less pronounced clavate chambers, a more asymmetrical, and lower arched aperture and a less-well developed apertural lip. It is distinguished from Parasubbotina prebetica in having lower trochospiral coiling, a flat spiral side, 4- 41/2 rather than 41/2-5 chambers in the final whorl, chambers increasing gradually in size in the final whorl that are considerable less bulbous than in P. prebetica, a small umbilicus and a more equatorial position and higher arch-morphology of the aperture. DISCUSSION.- Blow (1979, p. 1 198- 1 199) remarked that the genus Clavigerinella appears in the record "without any transitional forms in terms of apertural characteristics" but nevertheless "some specimens of early forms included in the taxon Subbotina inaequispira (Subbotina). . . show some degree of radial elongation of the chambers combined with an aperture which is markedly asymmetrically placed with respect to the umbilicus", and he suggested that such forms might be ancestral. Toumarkine and Luterbacher (1985, fig. 22.19) illustrated a so-called "G. inaequispira - C. eocanica eocanica transition" which appears to be a sub-adult specimen of C. eocanica. Coxall and others (2003) erected the species Parasubbotina eoclava to include some forms previously included in P. inaequispira that they considered as distinct from the holotype morphology of that taxon and show some transitional features toward Clavigerinella, particularly the strongly asymmetrical aperture with its broad lip, the low trochospiral coiling, and the tendency for radially extended chambers. PHYLOGENETIC RELATIONSHIPS.- Parasubbotina eoclava evolved from P. inaequispira in the latest early Eocene and was ancestral to Clavigerinella eocaenica (Coxall and others, 2003). GEOGRAPHlC DISTRIBUTI0N.- Parasubbotina eoclava is known from relatively high productivity environments in the low to mid-latitudes, where it often co-occurs with Clavigerinella spp. (Coxall and others, 2003). STABLE ISOTOPE PALEOBIOL0GY.- This species was recorded with more positive ò18O and more negative ò13C than coexisting Turborotalia frontosa, indicating a cold water sub-thermocline or upwelling environment (Coxall and others, 2003).
Systematics:

35
 Ordo Foraminiferida
  Superfamilia Globigerinaceae
   Familia Globigerinidae
    Genus Parasubbotina
     Species Parasubbotina eoclava
Synonym list:
Pearson et al. (2006):
p 1975 Clavigerinella? columbiana Petters. - McKeel & Lipps : p.258 pl. 4; fig. 6a, b (not pl. 3: fig. 8a-c = Globorotaloides eovariablis Huber and Pearson n. sp.) [lower middle Eocene Tyee Fm., Coast Ranges, Oregon]. [Not Petters, 19541.
p 1979 Subbotina inaequispira Subbotina. - Blow : p.1272 pl. 163; fig. 9-10 [Zone E8, Kane 9-Core 42, Endeavour seamount, eastern North Atlantic Ocean]. [Not Subbotina, 1953.]
2003 Parasubbotina eoclava Coxall et al.. - Coxall et al. : p.256 pl. 8; fig. 1-3 (holotype), 4-11 (paratype) [middle Eocene Zone E8, ODP Hole 865B, Allison Guyot, equatorial Pacific Ocean]
2004 Parasubbotina eoclava Coxall et al.. - Pearson et al. : p.36 pl. 1; fig. 14 [middle Eocene Zone E617, Tanzania]
2006 Parasubbotina eoclava Coxall et al.. - Pearson et al. : p.89 pl. 5.9; fig. 1-16 (Pl. 5.9, Figs. 1- 10: reillustration of holotype and paratypes of Parasubbotina eoclava Coxall, Huber and Pearson)
Specimen:
Smithsonian Museum of Natural History, Washington, D.C., Inventory number: USNM 517714
Smithsonian Museum of Natural History, Washington, D.C., Inventory number: USNM 517715
Smithsonian Museum of Natural History, Washington, D.C., Inventory number: USNM 517716
References:

McKeel,D.R.. and Lipps,J.H. (1975):
Eocene and Oligocene planktonic foraminifera from the central and southern Oregon coast range . Journal of Foraminiferal Research Vol. 5 p. 1-5

Blow,W.H. (1979):
The Cainozoic Globigerinida. 3 Vols p. 1413 pp

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.; Nicholas,C.J..; Singano,J.M..; Bown,P.R..; Coxali,H.K..; van Dongen,B.E..; Huber,B.T.; Karega,A..; Lees,J.A..; Misaky,E..; Pancost,R.D..; Pearson,M.. and Roberts,A.P.. (2004):
Paleogene and Cretaceous sediment cores from the Kilwa and Lindi areas of coastal Tanzania: Tanzania Drilling Project Sites 1-5 . Journal of African Earth Sciences Vol. 39 p. 25-62

Pearson,P.N.; Olsson,R.K.; Hemleben,C.; Huber,B.T. and Berggren,W.A. (2006):
Atlas of Eocene Planktonic Foraminifera. p. 1-513
Anonymous: Unedited TaxonConcept data
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