Catalog - Globoturborotalita paracancellata

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Globoturborotalita paracancellata

Citation: Globoturborotalita paracancellata Olsson & Hemleben, in Spezzaferri et al. 2018

Type specimens: Holotype (USNM 598584) and paratype (USNM 598585)

Type sample (& lithostrat): Atlantic Slope Project corehole 5B 10F/6-12”

Type locality: western Atlantic Ocean

Type repository: Washington, USNM

Type of wall: Normal perforate, spinose, ruber/sacculifer-type wall texture, an average of 17 pores/50 μm2 test surface area.

Test morphology: Low trochospiral, consisting of 3 whorls, globular, moderately lobulate profile, chambers globular; in spiral view 3½ globular, slightly embracing chambers in ultimate whorl, increasing rapidly in size, sutures depressed, straight; in umbilical view 3½ globular, slightly embracing chambers, increasing rapidly in size, sutures depressed, straight, umbilicus small, open, enclosed by surrounding chambers, aperture umbilical, a rounded arch, bordered by a thin thickened rim; in edge view chambers globular, slightly embracing, initial whorl of chambers flat.

Maximum diameter of holotype 0.43 mm, minimum diameter 0.32 mm, thickness 0.30 mm.

Named paracancellata because it evolves from G. cancellata

DISTINGUISHING FEATURES: Globoturborotalita paracancellata has a subbotinid-type morphology but differs in possessing a reticulate globoturborotalitid ruber/sacculifer-type wall and a thickened rim bordering the circular to moderately high arched aperture instead of a lip, as is typical of Subbotina. Globoturborotalita cancellata can be distinguished from G. paracancellata by having only 3½ chambers in the final whorl and a lower pore density than G. paracancellata. Globoturborotalita cancellata also has a generally smaller test. It differs from G. occlusa by the more open umbilical and higher arched aperture, bordered by a narrow rim that is absent in G. occlusa. It differs from G. woodi and G. brazieri by the lower arched aperture and by its 3½ chambers in the last whorl. G. connecta has a remarkably lower arched aperture. It differs from G. ouachitaensis also by its larger size and G. pseudopraebulloides Olsson and Hemleben n. sp. by having an apertural rim.

DISCUSSION: Blow and Banner (1962) derived “ Globigerinoides” from their subspecies Globigerina praebulloides occlusa. However, we do not retain here this lineage (see Chapter 9, this volume). According to our observations, the origin of the genus Trilobatus is preceded by morphotypes typified by Globoturborotalita paracancellata n. sp., which is hypothesized as the ancestral species.

PHYLOGENETIC RELATIONSHIPS: The species name paracancellata is chosen because it is believed that this species evolved from Globoturborotalita cancellata by a more rapid increase in chamber size and having 3½ chambers in the ultimate whorl and developing a ruber/sacculifer-type wall texture.

STRATIGRAPHIC RANGE: The illustrated specimens on Plate 8.12 range from Zone O1 to Zone O6. We have identified the species in samples from the uppermost Eocene Zone E16.

GEOGRAPHIC DISTRIBUTION: Known so far in the western Atlantic Ocean and the U.S. Gulf Coast. Probably widespread in low to middle latitudes due to its ancestry to Trilobatus primordius.

References:

Spezzaferri, S., Olsson, R. K., Hemleben, C., Wade, B. S. & Coxall, H. K. (2018d). Taxonomy, biostratigraphy, and phylogeny of Oligocene and Lower Miocene Globoturborotalita. In, Wade, B. S., Olsson, R. K., Pearson, P. N., Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 46(Chap 8): 231-268. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globoturborotalita paracancellata Olsson & Hemleben, in Spezzaferri et al. 2018

Globoturborotalita paracancellata

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