Catalog - Globorotalia humerosa

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Globorotalia humerosa

Citation: Globorotalia humerosa Takayanagi & Saito 1962

Type specimens: Holotype (figs. 1a-c), no. 75079: paratype (figs. 2a. b), no. 75078.

Type sample (& lithostrat): Holotype from sample A-16 and paratype from sample A-17; Nobori Formation.

Type age (chronostrat): Miocene. Tortonian, Globorotalia cultrata cultrata/Globigerina nepenthes Zone

Type locality: IGPS (Institute of Geology and Paleontology, Sendai) locality no. Ko-25; 33°22'09" N., 134°03'33" E. A cliff, 100 meters east of Nobori, Muroto City, Kochi Prefecture, Shikoku, Japan.

Type repository: Sendai; Deposited in the collections of the Institute of Geology and Paleontology. Tohoku University, Sendai, Japan:

Test low trochospiral. biconvex. but occasionally almost flat in spiral side, equatorial periphery lobate, axial periphery rounded: chambers ovate 10 to 14 arranged in about two whorls, usually six to seven in last whorl. chambers increasing in size in last whorl somewhat irregular, frequently last and/or penultimate chambers much reduced in xize compared with preceding ones in last whorl: last chamber occasionally somewhat protruding and tending to be displaced towards the umbilical side: sutures not limbate. radial to slightly curved, depressed on spiral side, radial to faintly curved, depressed on umbilical side: wall calcareous, thick, cancellate. surface granular in appearance umbilicus fairly wide and-deep, aperture medium to low arch. with a narrow distinct lip. interiomarginal, umbilical-extraumbilical. apertural openings of preceding chambers often connected with last one to make large channeled hollow: coiling of tests is mostly in right direction.

Maximum diameter of holotype 0.46 mm. maximum thickness 0.32 mm. Maximum diameter of paratype 0.44 mm., maximum thickness 0.31 mm.

Remarks: In general appearance, this species resembles Globigerina eggeri Rhumbler, but is distinguished by having the aperture with a distinct lip being interiomarginal, umbilical-extraumbilical in position. It differs from Globorotalia mayeri Cushman and Ellisor in having more inflated chambers, more convex spiral side, wider and deep umbilicus, and the thicker test with more granular appearance. It also differs from Globorotalia acostaensis Blow in having more chamber in the last whorl, usually with more than six chambers instead of five as in G. acostaensis, wider umbiIicus, less developed apertural lip. and wider apertural opening. Moreover, it is distinguishable from Globorotalia subcretacea (Lomnicki) by possessing a less lobulate equatorial profile, more chambers in the last whorl. and rather irregularly developed last and/or penultimate chambers. The development of the reduced chamber in the adult stage may possibly be one of the characteristics of the new species. The specimen figured by Hamilton as Globigerina subcretacea Lomnicki (1953) seems to be closely related and referable to the present form in showing the much reduced last two chambers.

Common

References:

Takayanagi, Y. & Saito, T. (1962). Planktonic foraminifera from the Nobori formation, Shikoku, Japan. Science Reports of the Tohoku University. 2(5): 67-105. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia humerosa Takayanagi & Saito 1962

Globorotalia humerosa

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