CATALOG OF ORIGINAL DESCRIPTIONS: Globotruncana dentata Hooper 1977
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Original Description Test low trochospiral, slightly lobulate, widely and deeply umbilicate, planoconvex with two and one-half to three whorls, double-keeled in early whorls and commonly single-keeled in last whorl; the six to seven chambers of last whorl expanding very regularly in size, so that ratio of diameter of last whorl to that of penultimate whorl (Da - D'a/Db - D'b, of Pessagno, 1967) is estimated to range approximately 1.6 to 1.9. Spiral side slightly convex at inner whorls, becoming planiform or even concave at the outer; curved, raised, beaded sutures; chambers spirally crescent-shaped, but may become somewhat petaloid later; surfaces smooth, flat in earlier whorls, becoming concave later. Umbilical side highly convex, especially last few chambers; angle XDU of Pessagno (1967) increasing from about 45° at beginning of last whorl to about 85° at last formed chamber; chambers crudely subrectangular tending to become shaped like human canine tooth in last part of last whorl; sutures slightly depressed, but commonly partially filled with curved, beaded ridge extending in arc from umbilical shoulders to merge with keel; umbilical surface rugose. Primary aperture interiomarginal, umbilical; tegilla commonly broken off, leaving a flange, but infralaminal apertures sometimes indicated at margins of flanges. Size: Measured diameters of seven specimens range from 0.65 to 0.75 mm. Extra details from original publication Comparison with other species: Globotruncana dentata Hooper. n. sp. appears to be closely related to G. ventricosa White, a species that also possesses a G. linneiana early stage. The early double keel of G. dentata commonly is modified to form a single keel in the final whorl. whereas the keel of G. ventricosa is always double. Globotruncana dentata has a Da - D'a/Db- D'b ratio ranging from 1.6 to 1.9. a value that is very close to the 1. 7 to 2.1 range of G. ventricosa. This species is also similar to the form figured as G. paraventricosa (Hofker) by Edgell (1957) from the Campanian of Western Australia. However. G. paraventricosa has 8 chambers in the final whorl. a somewhat convex spiral side. and a double keel throughout and thus differs from G. dentata. Globotruncana dentata also bears a superficial resemblance to G. elevata (Brotzen) which has a similar Da- D'a/Db - D'b ratio. but the latter species is sing le-keeled throughout. G. dentata chiefly differs from G. concavata (Brotzen) = Marginotruncana concavata (Brotzen) of Pessagno by having a single rather than narrow double keel in the final whorl of mature specimens and in having less rapidly expanding chambers.
References:
Hooper, K. (1977). Globotruncana dentate, a new species of Planktonic foraminifer from the Toolonga Calcilutite of Western Australia. Micropaleontology. 23(3): 361-364. gs
Globotruncana dentata compiled by the pforams@mikrotax project teamviewed: 23-4-2025
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