pforams@mikrotax - Trilobatus immaturus

Citation: Trilobatus immaturus (LeRoy, 1939)

Basionym: Globigerinoides sacculiferus (Brady) var. immaturus LeRoy, 1939

Synonyms:

Globigerinoides sacculiferus (Brady) var. immatura LeRoy, 1939:236, pl. 3, figs. 19-21 [Miocene, Rokan-Tapanoeli area, Central Sumatra, Indonesia].
Globigerinoides trilobus immaturus LeRoy.—Keller, 1981, pl. 1 [lower Miocene Zone N4, DSDP Site 292, northwest Pacific Ocean].—Bolli and Saunders, 1985, fig. 20(14) [holotype re-illustrated].
Globigerinoides immaturus LeRoy.—Kennett and Srinivasan, 1983:64, pl. 10, fig.3; pl. 13, figs. 7-9 [upper Miocene Zone N16, DSDP Site 289, Ontong Java Plateau, western equatorial Pacific Ocean].—Spezzaferri, 1994:37, pl. 13, figs. 3a-c [lower Miocene, Subzone N4a, DSDP Hole 516F, southeastern Atlantic Ocean].

Taxonomic discussion:

There is little consensus on how many species to recognise within this group. In the modern ocean the sacculifer, quadrilobatus, immaturus and trilobus test morphotypes are all produced by the same species (Andre et al. 2013), and so are no longer separated by biologists. They are, however, used by palaeontologists including Spezzaferri et al. (2018) and Poole & Wade (2019). [editor's comment - JRY 2018]

LeRoy (1939) described this form from Sumatra, Java and Borneo, and considered it either an immature form of T. sacculifer, or a T. sacculifer lacking the typical sac-like chamber due to ecological influence. Kennett and Srinivasan (1983), described a lineage consisting of trilobus-immaturus-quadrilobatus-sacculifer. However, successive observations in Spezzaferri (1994) show that the base of T. immaturus preceded the base of T. trilobus. Therefore the lineage of Kennett and Srinivasan (1983) is not retained. [Spezzaferri et al. 2018]

Distinguishing features:
Parent taxon (Trilobatus): Supplementary apertures and cancellate wall.
This taxon: Like T. trilobus but slightly more lobate and the primary aperture is a low umbilical arch across the antepenultimate chamber.

Description

Although very similar to T. trilobus (Bolli and Saunders, 1985) this species is slightly more lobate and the primary aperture is a low umbilical arch across the antepenultimate chamber, whereas in T. trilobus it is an elongated slit encompassing the penultimate and antepenultimate chambers. Although Bolli (1957) distinguished T. trilobus from T. immaturus by the larger last chamber in T. trilobus, this criterion is not retained here because of large size variability of the last chamber in both species. It differs from T. altospiralis n. sp. by having 3-3½ chambers in the last whorl instead of 4, by its less lobulate profile, and a more elongated subrectangular outline. It differs from T. subsacculifer because it lacks the last sac-like chamber and for its more elongated profile. [Spezzaferri et al. 2018]

Low trochospiral, consisting of about 2½-3 whorls, subrectangular to ovate, moderately lobulate in outline, chambers globular; 3½ subspherical chambers in the last whorl, increasing moderately to rapidly in size. Sutures depressed, straight to slightly curved on both sides, umbilicus narrow and tending to close. Primary aperture umbilical, a low arch tending to become extraumbilical and encompassing the antepenultimate chamber, sometimes bordered by a thin rim. A single small to medium sized slightly arched supplementary aperture is placed over the sutures separating the last and the penultimate chamber. Rarely two supplementary apertures are present. [Spezzaferri et al. 2018]

Normal perforate, spinose, sacculifer-type wall.

Height of holotype 0.43 mm. [Spezzaferri et al. 2018]

Biogeography and Palaeobiology

Cosmopolitan but more abundant at middle and low latitudes. [Spezzaferri et al. 2018]

This species records the lowest δ18O values and high δ13C values within the assemblages where it is found (Gasperi and Kennett, 1993). Nikolaev and others (1998) indicate a surface habitat range of this species between 25 and 100 m. [Spezzaferri et al. 2018]

It evolved from T. primordius just above the base of Subzone M1a and probably gave origin to T. trilobus. [Spezzaferri et al. 2018]

Biostratigraphic distribution

Geological Range:
Notes: From the lower Miocene lower part of Subzone M1a (Spezzaferri, 1994) to the Recent (e.g., Bolli and Saunders, 1985). The FO of T. trilobus s. l. given in Wade and others (2011) at 23.73 Ma. However, this datum is based on the taxonomic concept of Pearson and Chaisson (1997) that lumps T. trilobus and T. immaturus, and was astronomically calibrated by Shackleton and others (2000). Since the FO of T. immaturus is observed before the FO of T. trilobus, the datum of 23.73 Ma is here retained for the FO of T. immaturus. [Spezzaferri et al. 2018]
Last occurrence (top): Non-extinct palaeontological taxon. Data source: Brummer & Kucera 2022: The morphotype occurs at the present day but is formed by the species T. sacculifer, so this taxon is not used by biologists
First occurrence (base): within M1a subzone (22.44-22.96Ma, base in Aquitanian stage). Data source: Spezzaferri et al. 2018

Primary source for this page: Spezzaferri et al. 2018 - Olig Atlas chap.9 p.289

References:

Bolli, H. M. & Saunders, J. B. (1985). Oligocene to Holocene low latitude planktic foraminifera. In, Bolli, H. M., Saunders, J. B. & Perch-Neilsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge, UK 155-262. gs

Bolli, H. M. (1957b). Planktonic foraminifera from the Oligocene-Miocene Cipero and Lengua formations of Trinidad, B.W.I. 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: 97-123. gs

Brummer, G-J. A. & Kucera, M. (2022). Taxonomic review of living planktonic foraminifera. Journal of Micropalaeontology. 41: 29-74. gs

Gasperi, J. T. & Kennett, J. P. (1993). Vertical thermal structure evolution of Miocene surface waters; western Equatorial Pacific DSDP Site 289. Marine Micropaleontology. 22: 235-254. gs

Keller, G. (1981a). Origin and evolution of the genus Globigerinoides in the Early Miocene of the northwestern Pacific, DSDP Site 292. Micropaleontology. 27(3): 293-304. gs

Kennett, J. P. & Srinivasan, M. S. (1983). Neogene Planktonic Foraminifera. Hutchinson Ross Publishing Co., Stroudsburg, Pennsylvania. 1-265. gs

LeRoy, L. W. (1939). Some small foraminifera ostracoda and otoliths from the Neogene (Miocene) of the Rokan-Tapanoeli area, central Sumatra,. Natuurkunde Tijdschrift voor Nederlandsch-Indië. 99(6): 215-296. gs

Nikolaev, S. D., Oskina, N. S., Blyum, N. S. & Bubenshchikova, N. V. (1998). Neogene-Quaternary variations of the ‘Pole-Equator’ temperature gradient of the surface oceanic waters in the North Atlantic and North Pacific. Global and Planetary Change. 18: 85-11. gs

Pearson, P. N. & Chaisson, W. P. (1997). Late Paleocene to middle Miocene planktonic foraminifer biostratigraphy, Ceara Rise. Proceedings of the Ocean Drilling Program, Scientific Results. 154: 33-68. gs

Poole, C. R. & Wade, B. S. (2019). Systematic taxonomy of the Trilobatus sacculifer plexus and descendant Globigerinoidesella fistulosa (planktonic foraminifera). Journal of Systematic Palaeontology. 1-42. gs

Postuma, J. A. (1971). Manual of planktonic foraminifera. Elsevier for Shell Group, The Hague. 1-406. gs

Shackleton, N. J., Hall, M. A., Raffi, I., Tauxe, L. & Zachos, J. (2000). Astronomical calibration age for the Oligocene/Miocene boundary. Geology. 28: 447-450. gs

Spezzaferri, S. (1994). Planktonic foraminiferal biostratigraphy and taxonomy of the Oligocene and lower Miocene in the oceanic record. An overview. Palaeontographia Italica. 81: 1-187. gs

Spezzaferri, S., Olsson, R. K. & Hemleben, C. (2018c). Taxonomy, biostratigraphy, and phylogeny of Oligocene to Lower Miocene Globigerinoides and Trilobatus. 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 9): 269-306. gs

Wade, B. S., Pearson, P. N., Berggren, W. A. & Pälike, H. (2011). Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale. Earth-Science Reviews. 104: 111-142. gs

test outline:	Lobate	chamber arrangement:	Trochospiral	edge view:	Equally biconvex	aperture:	Umbilical
sp chamber shape:	Globular	coiling axis:	Low-moderate	periphery:	N/A	aperture border:	Thin lip
umb chbr shape:	Globular	umbilicus:	Wide	periph margin shape:	Broadly rounded	accessory apertures:	Sutural
spiral sutures:	Moderately depressed	umb depth:	Deep	wall texture:	Cancellate	shell porosity:	Macroperforate: >2.5µm
umbilical or test sutures:	Strongly depressed	final-whorl chambers:	3.5-3.5	N.B. These characters are used for advanced search. N/A - not applicable

Trilobatus immaturus

Taxonomy

Description

Biogeography and Palaeobiology

Biostratigraphic distribution

References:

Add Comment

Comments