Trilobatus praeimmaturus


Classification: pf_cenozoic -> Globigerinidae -> Trilobatus -> Trilobatus praeimmaturus
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 praeimmaturus (Brönnimann and Resig, 1971)
Rank: species
Basionym: Globigerinoides quadrilobatus praeimmaturus Brönnimann and Resig, 1971
Synonyms:
Taxonomic discussion:

Brönnimann and Resig (1971) considered this form as a subspecies of T. quadrilobatus and related it to T. quadrilobatus immaturus. The holotype they describe is covered by a relatively thick cortex (“secondary shell substance”) concealing the sutures of the last whorl. Trilobatus praeimmaturus has been overlooked and possibly attributed to other Globigerinoides species, although it is relatively abundant. [Spezzaferri et al. 2018]

Catalog entries: Globigerinoides quadrilobatus praeimmaturus

Type images:

Distinguishing features: Like T. immaturus and T. trilobus but more subcircular and compact outline; aperture slit-like encompassing the penultimate chamber, and usually 4 chambers in the final whorl.

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:

Trilobatus praeimmaturus is distinguished form T. immaturus and T. trilobus by its more subcircular and compact outline, by the slit-like aperture encompassing the penultimate chamber, and by having mainly 4 chambers in the last whorl. [Spezzaferri et al. 2018]


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

Test morphology: Low trochospiral, subglobular to ovate, compact in outline consisting of about 2½-3 whorls, 3½-4 subglobular chambers in the last whorl, increasing rapidly in size. Sutures depressed, straight to slightly curved on both sides, umbilicus narrow and tending to close. Primary aperture umbilical to extraumbilical, a low arch encompassing the penultimate chamber, and lacking any lip or rim but sometimes showing short blunt or composite pustules fused together. A single triangular slit-like to low arched supplementary aperture is placed over the sutures separating the last and the penultimate chamber. [Spezzaferri et al. 2018]

Size: Maximum diameter of holotype 0.22 mm, its axial height is about 0.19 mm. [Spezzaferri et al. 2018]

Character matrix

test outline:Ovatechamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical-extraumbilical
sp chamber shape:Globularcoiling axis:Low-moderateperiphery:N/Aaperture border:
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:3.5-4.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: Cosmopolitan, abundant in the South Atlantic and southwestern Pacific Oceans. [Spezzaferri et al. 2018]

Isotope paleobiology: No data available. [Spezzaferri et al. 2018]

Phylogenetic relations: Trilobatus praeimmaturus evolved from T. immaturus in the middle part of Subzones M1b. [Spezzaferri et al. 2018]

Most likely ancestor: Trilobatus immaturus - at confidence level 3 (out of 5). Data source: Spezzaferri et al. 2018.

Biostratigraphic distribution

Geological Range:
Notes: From the middle part of Subzone M1b to Zone M5 (Brönnimann and Resig, 1971). Additional investigations are needed to prove its presence in younger Miocene sediment. [Spezzaferri et al. 2018]
Last occurrence (top): within M5 zone (15.10-16.38Ma, top in Langhian stage). Data source: Spezzaferri et al. 2018
First occurrence (base): within M1b subzone (21.12-22.44Ma, 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.292

References:

Brönnimann, P. & Resig, J. (1971). A Neogene globigerinacean biochronologic time-scale of the southwestern Pacific. Initial Reports of the Deep Sea Drilling Project. 7(2): 1235-1469. 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


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

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Short stable page link: http://mikrotax.org/pforams/index.php?id=104366 Go to Archive.is to create a permanent copy of this page - citation notes



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