Catalog - Globigerina triloculinoides

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.

Globigerina triloculinoides

Citation: Globigerina triloculinoides Plummer 1927

Type specimens: PI.VIII, figs. 10a-c; 33076

Type locality: Zone P2, Wills Point Fm., Midway Group, Navarro Co., NE Texas, Station 23

Type repository: Washington; USNM

Test spiral, trochoid, composed of about 2 convolutions, the last of which is composed of 3½ very rapidly increasing and highly globose chambers; periphery very broadly rounded and distinctly lobate; shell surface strongly reticulate; superior face rounded with a very low spire of neatly coiled tiny chambers of the preceding whorl; inferior face rounded with a very shallow umbilical depression; aperture a small arched slit on the last chamber and edged with a more or less prominent, delicately notched flap that extends from a point near the periphery to the umbilical depression.

Greatest diameter up to .35 mm; usually less.

Globigerina triloba Egger, 1899, Abh. k. bay. Akad. Wiss., Cl. 2, vol.21,pt.1,p. 171,pi.21,fig.8.
Globigerina bulloides Cushman,1920,U.S.Geol.SurveyProf.Paper 128, p. 68, pi. 11, fig. 6.

The somewhat similar species, G. triloba Reuss, shows but three visible chambers on both sides of the test, and this new name is created to include such similar structures as display plainly the chambers of the preceding convolution and but a single aperture. Cushman's G. bulloides of the north Pacific (U. S. Nat. Mus., Bull. 71, pt. 4, p. 5, pi. 2, figs. 7-9) has an arrangement of chambers much like that of thisnewspecies,butithasmultipleaperturesopeninginto the umbilicus. The Miocene form described by Cushman also has the characteristic structure of G. triloculinoides, but the apertural features have not been included in his description,and it is doubtful whether his form should be here included in the synonymy. The presence of the conspicuous apertural flap appears somewhat unusual in the Globigerine series, and its degree of development in Midway material varies somewhat from a narrow lip to the wide flap herewith figured.

In the compact, siltless clays of the lower portion of the upper Midway zone, G. triloculinoides is most common. It is rare in the basal beds of the formation. Since no similar form has been seen in Cretaceous strata of this section, it aids in marking the Cretaceous-Eocene contact. In higher Eocene and in Oligocene strata in Texas a much larger species of this construction occurs commonly, but the umbilical lip is less conspicuous.

References:

Loeblich, A. R. & Tappan, H. (1957b). Planktonic foraminifera of Paleocene and early Eocene Age from the Gulf and Atlantic coastal plains. In, Loeblich, A. R. , Jr., Tappan, H., Beckmann, J. P., Bolli, H. M., Montanaro Gallitelli, E. & Troelsen, J. C. (eds) Studies in Foraminifera. U.S. National Museum Bulletin . 215: 173-198. gs

Olsson, R. K., Hemleben, C., Berggren, W. A. & Huber, B. T. (1999). Atlas of Paleocene Planktonic Foraminifera. Smithsonian Institution Press, Washington, DC. (85): 1-252. gs

Plummer, H. J. (1927). Foraminifera of the Midway Formation in Texas. University of Texas Bulletin. 2644: 1-206. gs O

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina triloculinoides Plummer 1927

Globigerina triloculinoides

References:

Add Comment

Comments