Trilobatus immaturus


Classification: pf_cenozoic -> Globigerinidae -> Trilobatus -> Trilobatus immaturus
Sister taxa: T. sacculifer, T. quadrilobatus, T. immaturus, T. trilobus, T. bisphericus, T. sicanus, T. altospiralis, T. praeimmaturus, T. primordius, T. subsacculifer, T. sp.,

Taxonomy

Citation: Trilobatus immaturus (LeRoy, 1939)
Rank: species
Basionym: Globigerinoides sacculiferus (Brady) var. immaturus LeRoy, 1939
Synonyms:
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]

Catalog entries: Globigerinoides sacculiferus immatura

Type images:

Distinguishing features: Like T. trilobus but slightly more lobate and the primary aperture is a low umbilical arch across the antepenultimate chamber.

NB These concise distinguishing features statements are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus.
They are being edited as the site is developed and comments on them are especially welcome.

Description


Diagnostic characters:

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]


Wall type: Normal perforate, spinose, sacculifer-type wall.

Test morphology: 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]

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

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical
sp chamber shape:Globularcoiling axis:Low-moderateperiphery:N/Aaperture border:Thin lip
umb chbr shape:Globularumbilicus:Wideperiph margin shape:Broadly roundedaccessory apertures:Sutural
spiral sutures:Moderately depressedumb depth:Deepwall texture:Cancellateshell porosity:Macroperforate: >2.5µm
umbilical or test sutures:Strongly depressedfinal-whorl chambers:3.5-3.5 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


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

Isotope paleobiology: 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]

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

Most likely ancestor: Trilobatus primordius - at confidence level 4 (out of 5). Data source: Spezzaferri et al. 2018.
Likely descendants: Trilobatus praeimmaturus; Trilobatus trilobus;

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): Extant Data source: Spezzaferri et al. 2018
First occurrence (base): within M1a subzone (22.44-22.96Ma, base in Aquitanian stage). Data source: Spezzaferri et al. 2018

Plot of occurrence data:

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

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. (1981). 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,. Natuurk. Tijdschr. Nederl.-Indie.. 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. 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. (2018b). 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


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Trilobatus immaturus compiled by the pforams@mikrotax project team viewed: 17-10-2019

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