Globorotalia (Globorotalia) truncatulinoides truncatulinoides d'Orbigny 1839 from: Blow, W.H. (1969): Late middle Eocene to Recent planktonic foraminiferal biostratigraphy. In: Proceedings of the First International Conference on Planktonic Microfossils, Geneva 1967 Vol. 1 Eds: Bronnimann, P.Renz, H.H. p. 199-422 | . |
Notice: This catalogue page may contain unedited data.
|
Subspecies Globorotalia (Globorotalia) truncatulinoides truncatulinoides d'Orbigny 1839 |
|
|
|
| Alternative name: |
|
| Diagnosis / Definition: |
Blow (1969):
Description of neotype: Test coiled in a low trochospire with about 15 chambers comprising the spire and with 5 complete chambers in the last whorl; a small part of a sixth chamber is also visible in the last whorl. Dorsal side of the test flat to slightly concave; ventral side of the test strongly vaulted, acutely conical, so giving an essentially planoconvex test with a distinct carina in axial profile. In equatorial profile the test is not lobulate but almost polygonal in outline with the peripheral margins of the chambers almost flat not strongly curved. In dorsal aspect the chambers are closely appressed but not greatly embracing and not inflated. Dorsal intercameral sutures, radial, virtually straight except for slight retortion at their distal ends; dorsal sutures, slightly limbate and raised. Ventral intercameral sutures slightly incised, distinct, radial to sinuous peripherally. Ventral surfaces of the chambers not significantly inflated, rather compressed and appressed. Umbilicus deep, moderately widely open and sharply delimited by the sudden "in turning" of the umbilical shoulders of the enclosing chambers. The umbilical shoulders of the chambers are pointed and bear pustules. Aperture, interiomarginal, umbilicalextraumbilical, a low arch strictly limited to the basal suture ventral to the carina. Aperture bordered by an asymmetrical lip which is widest at its umbilical end. Relict apertures visible within the umbilicus and the umbilical ends of the earlier apertural lips are also visible. Wall calcareous, radial hyaline [62a], densely but comparatively finely perforate except on the apertural face of the final chamber. The wall is strongly pustulose over the first three chambers of the final whorl immediately adjacent to the aperture. The pustules are densely packed but not fused together, each pustule being clearly delimited and separated one from the other. Pustules also present over the umbilical shoulders of the chambers of the last convolution and over the dorsal surfaces of the chambers of the penultimate whorl. The pores open between the pustules so that there is no significant area of the test without the normal wall pores which have unrestricted access to the exterior; the pores do not open into pore pits and do not seem to be modified in any way. Maximum diameter of holotype 0.78 mm. Neotype deposited in the British Museum (N.H.) registered no. 1968-3-27-2 (see also plate and figure explanations). |
| Discussion / Comments: |
Blow (1969):
Note: As discussed by BANNER and BLOW (1960, Contrib. Cushman Found. Foram. Res., vol. XI, Pt. I, P. 37) no syntypes exist Of D'ORBIGNY'S taxon Rotalina truncatulinoides and there is, therefore, no objective primary reference type for the taxon. With the recognition, in recent years, of "Globorotalia tosaensis" TAKAYANAGI and SAITO and the recognition in this work of other similar forms which are morphologically close to the concept of truncatulinoides as developed from, and subsequent to, the work Of CUSHMAN (1931, U.S. Nat. Mus. Bull. 104, pt. 8, p. 97), it has become imperative to erect a neotype for Rotalina truncatulinoides D'ORBIGNY, 1839. It should be borne in mind that the present concept of "Globorotalia truncatulinoides" dates only from CUSHMAN'S work in 1931 and although there has been considerable uniformity of concept expressed in the opinions of subsequent workers, there is no objective standard of reference to the real morphology of the taxon prior to the erection of a neotype in this work. It should be fülly realised that Rotalina truncatulinoides D'ORBIGNY, 1839, was not referred to by BRADY (1884) who considered this form referable to "Pulvinulina micheliana (D'ORBIGNY)" and it would seem thattheonlyfundamentalreason why CUSHMAN(193I,01) cit. supra) made anomenclatorial change for the form illustrated by BRADY (1884, Pl. 104, figures ia C, 2a b) was that ~~micheliana" is a Cretaceous species and that "truncatulinoides" is a Recent form. Little can be gained from a consideration Of D'ORBIGNY'S type figure except that the morphotype had a plano convex test with one sharply conical side. Such details of the aperture as given by D'ORBIGNY do not suggest reference of "R. truncatulinoides" to the Globorotaliidae but rather to the Cibicidininae; indeed, it is possible that D'ORBIGNY was really referring to a morphotype which, in present day nomenclature, would be referred to Cibicides refulgens! However, since so much literature has now accumulated all following the morphological concept of BRADY (for "P. micheliana of BRADY" non D'ORBIGNY) and the nomenclature Of CUSHMAN (1931), it is quite impossible to make any radical nomenclatorial or taxonomic changes for the form called "Globorotalia truncatulinoides" by so many authors. However, it is permissible to restrict the concept of G. (G.) truncatulinoides truncatulinoides by reference to a neotype which forms an objective reference Standard. In this regard, it is obvious from the synonymies quoted by many workers who have recorded "Globorotalia truncatulinoides" that they have based their morphological concept of the taxon purely on BRADY's figured forms of P. micheliana(sic.), changed only in nomenclature by reason Of CUSHMAN'S erection of the genus Globorotalia in 1927 and the assignation of BRADY's forms to this genus by CUSHMAN in 1931. Hence, the writer examined as many as possible of the forms selected and examined by BRADY prior to 1884, which were called by him "Pulvinulina micheliana", in order to fully appreciate BRADY'S concept of the morphotype. Unfortunately, BRADY did not select any specimens of "P. micheliana" from the area from which D'ORBIGNY described his taxon Rotalina truncatulinoides but the Challenger material from off Gomera, Canary Islands, is virtually topotypic for D'ORBIGNY's R. truncatulinoides. From this material, the writer has selected a specimen as neotype.
Remarks: The neotype of G. (G.) truncatulinoides truncatulinoides shows a normal wall texture and structure which is not thickened by a sheath like structure (cf. G. (G.) truncatulinoides pachytheca, see P. 4o5 below). The pustules although densely packed over the earlier parts of the test are clearly not fused together and they still show their individuality as drawn by BANNER for the neotype. In other specimens, such as that illustrated in apertural view by stereoscan (Pl. 49, figure 6), the individual nature of the pustules can be clearly seen although this form, in optical examination, appears to be as densely pustulose as the neotype for the region of the umbilical and ventral margins of the first and second chamber of the last whorl. Thus, in G. (G.) truncatulinoides truncatulinoides there is a normal perforate wall which is not overlain by an "imperforate" sheath like structure.
G. (G.) truncatulinoides truncatulinoides differs from G. (G.) truncatulinoides Pachytheca in characters other than the lack of the "imperforate" sheath like structure. Thus, truncatulinoides (sensu stricto) possesses more laterally compressed chambers in the final whorl, a more widely open umbilicus, a somewhat less tightly coiled test, less embracing chambers and more completely radial dorsal intercameral sutures. Further, the ventral side as a whole and the individual chambers on the ventral side are both more sharply and acutely conical in truncatulinoides (sensu stricto) than in pachytheca.
G. (G.) truncatulinoides truncatulinoides develops from G. (T.) tosaensis tenuitheca by the acquisition of an "imperforate" carina and the first appearance of the peripheral carina, no matter where or to what extent it is developed, is utilized to separate taxonomically the two taxa. There is a general trend for the umbilicus to increase in relative width and the test to become more ventrally conical with more laterally compressed chambers during the evolution of truncatulinoides from tenuitheca; this trend continuous subsequent to the first appearance of the carina and thus in forms referred here to G. (G.) truncatulinoides truncatulinoides.
Stratigraphical Range: Ranges from the base of Zone N.22 to Zone N.23. |
| Synonym list: |
Blow (1969):
Quilty (1976):
|
| References: |
d'Orbigny,A.D. (1839):
Foraminfčres des Iles Canaries.
In: Histoire naturelle des Iles Canaries Vol. 2(2) Eds: Barker Webb, P.Berthelot, S.
Brady,H.B. (1884):
Report on the foraminifera dredged by H.M.S. Challenger during the years 1873-1876.
In: Report of the scientific results of the voyage of H.M.S. Challenger, 1873-1876, Zoology Vol. 9 p. 1-814
Cushman,J.A. (1931):
The foraminifera of the Atlantic Ocean; Part VIII- Rotaliidae, Amphisteginidae, Calcarinidae, Cymbaloporettidae, Globorotaliidae, Anomalinidae, Planorbulinae, Rupertiidae and Homotremidae . United States National Museum Bulletin Vol. 104 p. 1-179
Blow,W.H. (1969):
Late middle Eocene to Recent planktonic foraminiferal biostratigraphy.
In: Proceedings of the First International Conference on Planktonic Microfossils, Geneva 1967 Vol. 1 Eds: Bronnimann, P.Renz, H.H. p. 199-422
Quilty,P.G.. (1976):
Planctonic foraminifera DSDP Leg 34- Nazca Plata . DSDP initial reports Vol. 34
|
This work is licensed under a Creative Commons Attribution 2.5 License.
|
|
Taxon Concept provided by