Type of wall: Normal perforate, cancellate, pustulose, probably spinose in life.

Test morphology: Test, compact, globular, chambers arranged in a tight, low trochospiral, subcircular to subquadrate in equatorial outline, moderately lobate; in spiral view 3-3½ ovoid compressed chambers in ultimate whorl, increasing rapidly in size, sutures straight or slightly curved, depressed; in umbilical view 3 ovoid chambers in ultimate whorl, increasing rapidly in size, sutures straight and incised, umbilicus moderate in size, aperture centered deep in the umbilicus, bordered by a thin, irregular, subtriangular-shaped lip or tooth which tends to point down the opposing suture; in edge view test oval in outline, chambers ovoid in shape, ultimate chamber projects above and bends over the umbilicus.

• Globigerina tripartita Koch.—Blow and Banner, 1962:96 (partim), pl. 10, figs. D-F [upper Eocene Cribrohantkenina danvillensis Zone, Lindi area, Tanzania].—Blow, 1969:322, pl. 16, fig. 6 [upper Eocene Zone P15, Lindi area, Tanzania].—Stainforth and others, 1975:325, 328 (partim), fig. 148, nos. 1, 6 [upper Eocene Globigerinatheka semi-involuta Zone, Navet Fm., Trinidad] (not fig. 148, nos 2-5, 7, 8 = Dentoglobigerina tripartita). [Not Koch, 1926.]
• Dentoglobigerina tripartita (Koch).—Blow, 1979:1310, pl. 244, figs. 3, 4 [upper Eocene Zone P16, Lindi area, Tanzania].—Olsson and others, 2006:408-410 (partim), pl. 13.3, figs. 4, 15 [upper Eocene Zone E16, Nanggulan Fm., Java], fig. 5 (reproduced from Blow, 1979, pl. 244, fig. 3), fig. 6 (reproduced from Blow, 1969, pl. 16, fig. 6), figs. 7, 8 [upper Eocene Zone E15/16, TDP Site 11, Tanzania], figs. 9-11 [upper Eocene Zone E15/E16, Shubuta Clay, Mississippi], fig. 14 [upper Eocene Zone E15, Istra More-4 well, Adriatic Sea] (Not pl. 13.3, figs. 1-3 = holotype; not pl. 13.3, figs. 12, 16 = Dentoglobigerina galavisi). [Not Koch, 1926.]
• Dentoglobigerina cf. tripartita (Koch).—Pearson and Wade, 2015:20, fig. 21.1 (reproduced from Blow, 1969, pl. 16, fig. 6), fig. 21.2 (reproduced from Blow, 1979, pl. 244, fig. 4), fig. 21.3a-b (reproduced from Olsson and others, 2006, pl. 13.3, figs. 7, 8), fig. 21.4a-7f [upper Eocene Zone E15/16, TDP Site 12, Tanzania] (Note fig. 21.4a-e = holotype designated here, NHMUK PM 71285; fig. 21.6a-b = paratype designated here, NHMUK PM 71286; fig. 21.7a-c = paratype designated here, NHMUK PM 71287).
• Dentoglobigerina pseudovenezuelana (Blow and Banner).—Olsson and others, 2006:404-408 (partim), pl. 13.2, figs. 9, 12 [upper Eocene Zone E15/16, Shubuta Clay, Wayne County, Mississippi]. [Not Blow and Banner, 1962.]

DISTINGUISHING FEATURES. Dentoglobigerina eotripartita is distinguished from D. galavisi by its more compact morphology with 3 tightly coiled, more rapidly increasing chamber size in the final whorl and by possessing a more overarching and compressed final chamber. This species differs from D. tripartita by its smaller size, and less spherical, less compressed/reniform overall morphology, and from D. pseudovenezuelana by more tightly coiled chambers and tooth pointing down the opposing suture.

DISCUSSION. This species was initially identified in the Atlas of Eocene Planktonic Foraminifera (2006) as D. tripartita (Koch). At that time, an SEM of the tripartita holotype was unavailable and identification relied on a drawing of the holotype by Blow and Banner (1962), which was interpreted as a slightly deformed specimen, so we followed the well defined concept of this species set out by Blow (1969, 1979). The new holotype SEM of tripartita (Koch) (Pl. 11.14, Figs. 1-3) clearly shows, however, the large, robust, subspherical, test of this species, which is typical of the Oligocene, but is different from the specimens illustrated by Blow, and from D. cf. tripartita (Pearson and Wade, 2015). Dentoglobigerina eotripartita n. sp. is thus described to represent this smaller more compact morphotype typical of the Eocene, which was probably ancestral to the more robust tripartita sensu stricto.

PHYLOGENETIC RELATIONSHIPS. Dentoglobigerina eotripartita n. sp. descended from D. galavisi in the middle Eocene (Olsson and others, 2006) and probably gave rise to D. tripartita in the lower Oligocene (Pearson and Wade, 2015).

STRATIGRAPHIC RANGE. The first appearance is in upper Eocene Zone E14 according to Olsson and others (2006) although the oldest figured specimen is from Zone E15 (Olsson and others, 2006, pl. 13.3, fig. 4). This form probably developed gradually into D. tripartita by becoming larger and more spherical. All of our illustrated specimens are from the upper Eocene, but the eotripartita like morphology persists in the record until at least the upper Oligocene Zone O7 (see the dissections of Blow, 1969, pl. 29, figs. 3 and 5, and the discussion under tripartita). Our youngest confirmed occurrence is from Zone O1.

GEOGRAPHIC DISTRIBUTION. Global at low to mid-latitudes.

STABLE ISOTOPE PALEOBIOLOGY. Stable isotope data indicate a thermocline habitat, becoming deeper with increasing test size (Wade and Pearson, 2008, recorded as D. tripartita; see also Pearson and Wade, 2015).

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