CATALOG OF ORIGINAL DESCRIPTIONS: Marginotruncana arcaformis Hofker 1978

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.

Higher levels: pf_cat -> M -> Marginotruncana -> Marginotruncana arcaformis
Other pages this level: M. arcaformis, M. bouldinensis, M. caronae, M. paraconcavata, M. paraconcavata veronikae, M. paraventricosa, M. pauperata, M. pileoliformis, M. pseudolinneiana, M. pseudomarginata, M. scorpionis, M. sinuosa,

Marginotruncana arcaformis

Citation: Marginotruncana arcaformis Hofker 1978
Rank: Species
Type locality: Shatsky Rise, northern Pacific Ocean.; 2689 m . deep; lat. 32°26.9' N., long. 157°42.7' E.
Type age: lower part of the M. mayaroensisZone
Type sample and level: DSDP 47.2-13-3 127-129cm
Holotype Repository: Depository not given [probably deposited in the author's collection].
Type & figured specimens: Pl. 2, Fig. 1

Current identification/main database link: Globotruncana bulloides Vogler, 1941

Original Description
Test rounded, compressed, with 5-6 chambers in the last-formed whorl; dorsal side slightly more convex than the ventral one; periphery lobulate. At the dorsal side the strongly rounded and thickened sutures go over into the dorsal keel of the marginal poreless plate; the ventral keel of that plate is slightly more centrally placed and thus seen together with the dorsal keel at the ventral side. Older chambers show a more or less distinct pustulose keel bordering the ventral chamber wall from the apertural lips which partly cover the umbilical hollow. Pores distinct, at the ventral side not drawn into an angle towards the proximal side of the chamber wall, but forming a rounded pore field. Keels of the marginal plate crenulate.

Size: Longer diameter of the tests about 45 mm, thickness about 15 mm, with the distinctly protruding apertural lips somewhat thicker.

Extra details from original publication
In the M. mayaroensis Zone of the upper Maastrichtian, globotruncanids with the characteristics of Marginotruncana are the only species found. This genus is characterised in that the ventral chamber walls are rounded or trapezoidal and the pore fields are rounded towards the umbilical cavity. In Globotruncana s.s.. the chamber walls at the ventral side are petaloid, because they form a proximal, umbilical, drawn-out angle and the pore fields follow this pattern. These two genera of globotruncanid species have demonstrably different ancestors.

In available topotype specimens from the Mendez Shale, Mexico, Globotruncana arca (Cushman), the genotype of Globotruncana, shows the characteristics of Globotruncana. However, all of the specimens from the M. mayaroensis Zone have the characteristics of Marginotruncana. Such a specimen was figured by Olsson and it is obvious that this is a species which greatly differs from the type.


Hofker, J. (1978). Analysis of a large succession of samples through the Upper Maastrichtian and Lower Tertiary of Drill Hole 47.2, Shatsky Rise, Pacific, Deep Sea Drilling Project. Journal of Foraminiferal Research. 8(1): 46-75. gs :: ::


Marginotruncana arcaformis compiled by the pforams@mikrotax project team viewed: 4-6-2020

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